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Reader-Writer Concurrency

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By Honnappa Nagarahalli

As an increasingly higher number of cores are packed together in a SoC, thread synchronization plays a key role in scalability of the application. In the context of networking applications, because of the  partitioning of the application into control plane (write-mostly threads) and data plane (read-mostly  threads), reader-writer concurrency is a frequently encountered thread synchronization use case.  Without an effective solution for reader-writer concurrency, the application will end up with: 

  • race conditions, which are hard to solve 
  • unnecessary/excessive validations in the reader, resulting in degraded performance excessive use of memory barriers, affecting the performance 
  • and, finally, code that is hard to understand and maintain 

In this blog, I will 

  • briefly introduce the reader-writer concurrency problem 
  • talk about solving reader-writer concurrency using full memory barriers and the C11 memory  model 
  • and, talk about complex scenarios that exist 

Problem Statement 

Consider two or more threads or processes sharing memory. Writer threads/processes (writers) update a data structure in shared memory in order to convey information to readers. Reader threads/processes (readers) read the same data structure to carry out some action. E.g.: in the context of a networking  application, the writer could be a control plane thread writing to a hash table, the reader could be a data  plane thread performing lookups in the hash table to identify an action to take on a packet. 

Essentially, the writer wants to communicate some data to the reader. It must be done such that the  reader observes the data consistently and atomically instead of observing an incomplete or  intermediate state of data. 

This problem can easily be solved using a reader-writer lock. But locks have scalability problems, and a  lock free solution is required so that performance scales linearly with the number of readers. 

Solution 

In order to communicate the ‘data’ atomically, a ‘guard variable’ can be used. Consider the following  diagram.

The writer sets the guard variable atomically after it writes the data. The write barrier between the two  ensures that the store to data completes before the store to guard variable. 

The reader reads the guard variable atomically and checks if it is set. If it is set, indicating that the writer  has completed writing data, the reader can read the data. The read barrier between the two ensures  that the load of data starts only after the guard variable has been loaded. i.e. the reader is prevented  from reading data (speculatively or due to reordering) till the guard variable is set. There is no need for any additional validations in the reader. 

As shown, the writer and the reader synchronize with each other using the guard variable. The use of  the guard variable ensures that the data is available to the reader atomically irrespective of the size of  the data. There is no need of any additional barriers in the writer or the reader. 

Some of the CPU architectures enforce the program order for memory operations in the writer and the  reader without the need for explicit barriers. However, since the compiler can introduce re-ordering, the  compiler barriers are required on such architectures. 

So, when working on a reader-writer concurrency use-case, the first step is to identify the ‘data’ and the  ‘guard variable’. 

Solving reader-writer concurrency using C11 memory model 

In the above algorithm, the read and write barriers can be implemented as full barriers. However, full  barriers are not necessary. The ordering needs to be enforced between the memory operations on the  data (and other operations dependent on data) and the guard variable. Other independent memory  operations need not be ordered with respect to memory operations on data or guard variable. This provides CPU micro-architectures more flexibility in re-ordering the operations while executing the  code. C11 memory model allows for expressing such behaviors. In particular, C11 memory model allows  for replacing the full barriers with one-way barriers. 

As shown above, the writer uses the atomic_store_explicit function with memory_order_release to set  the guard variable. This ensures that the write to data completes before the write to guard variable completes while allowing for later memory operations to hoist above the barrier. 

The reader uses the atomic_load_explicit function with memory_order_acquire to load the guard  variable. This ensures that the load of the data starts only after the load of the guard variable completes while allowing for the earlier operations to sink below the barrier. 

atomic_store_explicit and atomic_load_explicit functions ensure that the operations are atomic and  enforce the required compiler barriers implicitly. 

Challenges 

The above paragraphs did not go into various details associated with data. The contents of data, support  for atomic operations in the CPU architecture, and support for APIs to modify the data can present various challenges. 

Size of data is more than the size of atomic operations 

Consider data of the following structure.

The size of the data is 160 bits, which is more than the size of the atomic operations supported by the CPU architectures. In this case, the guard variable is required to communicate the data atomically to the  reader. 

If support required is for add API alone, the basic algorithm described in above paragraphs is sufficient.  The following code shows the implementation of writer and reader. 

However, several challenges exist if one wants to support an API to modify/update data depending on  the total size of modifications. 

Size of the modified elements is larger than the size of atomic operations

Let us consider the case when the total size of modifications is more than the size of atomic operations supported. 

Since all modified elements of data need to be observed by the reader atomically, a new copy of the  data needs to be created. This new copy can consist of a mix of modified and unmodified elements. The  guard variable can be a pointer to data or any atomically modifiable variable used to derive the address  of data, for ex: an index into an array. After the new copy is created, the writer updates the guard  variable to point to the new data. This ensures that, the modified data is observed by the reader  atomically.

As shown above, the elements b, c and d need to be updated. Memory at addr 0x200 is allocated for the  new copy of data. Element a is copied from the current data. Elements b, c and d are updated with new  values in the new copy of data. The guard variable is updated with the new memory address 0x200. This  ensures that the modifications of the elements b, c and d appear atomically to the reader. 

In the reader, there is dependency between data and the guard variable as data cannot be loaded  without loading the guard variable. Hence, the barrier between the load of the guard variable and data  is not required. While using C11 memory model, memory_order_relaxed can be used to load the guard  variable. 

The following code shows the implementation of writer and reader.

Note that, the writer must ensure that all the readers have stopped referencing the memory containing  the old data before freeing it. 

Size of the modified elements is equal to the size of atomic operations 

Now, consider the case when the total size of modifications is equal to the size of atomic operations supported. 

Such modifications do not need a new copy of data as the atomic operations supported by the CPU  architecture ensure that the updates are observed by the reader atomically. These updates must use  atomic operations. 

As shown above, if only element b has to be updated, it can be updated atomically without creating a  new copy of data in the writer. The store and load operations in writer and reader do not require any  barriers. memory_order_relaxed can be used with atomic_store_explicit and atomic_load_explicit  functions. 

Size of data is equal to the size of atomic operations 

Consider a structure for data as follows 

The size of the data is 64 bits. All modern CPU architectures support 64 bit atomic operations. 

In this case, there is no need of a separate guard variable for both add and modify APIs. Atomic store of  the data in writer and atomic load of the data in reader is sufficient. The store and load operations do  not require any barrier in the writer or reader either. memory_order_relaxed can be used with both  atomic_store_explicit and atomic_load_explicit functions. As shown above, if required, part of the data  can indicate if it contains valid data. 

Conclusion 

So, whenever faced with a reader-writer synchronization issue, identify the data, consider if a guard  variable is required. Keep in mind that what matters is the ordering of memory operations and not when  the data is visible to the reader. Following the methods mentioned above will ensure that unnecessary  barriers and validations are avoided, and the code is race free and optimized.

Community Issues DPDK 21.05 Release

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By Thomas Monjalon, DPDK Tech Board

A new DPDK release is now available, 21.05:  https://fast.dpdk.org/rel/dpdk-21.05.tar.xz

It was a quite big cycle, as is typical with our May releases:

  •  1352 commits from 176 authors
  •   2396 files changed, 134413 insertions(+), 63913 deletions(-)

There are no plans to start a maintenance branch for 21.05, and this version is ABI-compatible with 20.11 and 21.02.

Below are some new features:

  • General
    • compilation support for GCC 11, clang 12 and Alpine Linux
    •  mass renaming of lib directories
    • allow disabling some libraries
    • log names alignment and help command
    •  phase-fair lock
    • Marvell CN10K driver
  • Networking
    • predictable RSS
    •  port representor syntax for sub-function and multi-host
    • metering extended to flow rule matching
    • packet integrity in flow rule matching
    •  TCP connection tracking offload with flow rule
    •  Windows support of ice, pcap and vmxnet3 drivers

More details in the release notes:  https://doc.dpdk.org/guides/rel_notes/release_21_05.html

There are 41 new contributors (including authors, reviewers and testers)!  Welcome to Alexandre Ferrieux, Amir Shay, Ashish Paul, Ashwin Sekhar T K, Chaoyong He, David Bouyeure, Dheemanth Mallikarjun, Elad Nachman, Gabriel Ganne, Haifei Luo, Hengjian Zhang, Jie Wang, John Hurley, Joshua Hay, Junjie Wan, Kai Ji, Kamil Vojanec, Kathleen Capella, Keiichi Watanabe, Luc Pelletier, Maciej Machnikowski, Piotr Kubaj, Pu Xu, Richael Zhuang, Robert Malz, Roy Shterman, Salem Sol, Shay Agroskin, Shun Hao, Siwar Zitouni, Smadar Fuks, Sridhar Samudrala, Srikanth Yalavarthi, Stanislaw Kardach, Stefan Wegrzyn, Tengfei Zhang, Tianyu Li, Vidya Sagar Velumuri, Vishwas Danivas, Wenwu Ma and Yan Xia.

Below is the percentage of commits per employer company:

Based on Reviewed-by and Acked-by tags, the top non-PMD reviewers are:

         46     Ferruh Yigit 
         39     David Marchand 
         34     Andrew Rybchenko 
         30     Bruce Richardson
         27     Maxime Coquelin 
         26     Viacheslav Ovsiienko
         25     Akhil Goyal 
         23     Thomas Monjalon 
         22     Jerin Jacob 
         20     Ajit Khaparde 
         18     Xiaoyun Li 
         18     Anatoly Burakov 
         16     Ori Kam 
         12     Matan Azrad 
         12     Konstantin Ananyev 
         12     Honnappa Nagarahalli 
         11     Olivier Matz 
         11     Hemant Agrawal 
         10     Ruifeng Wang 

The new features for 21.08 may be submitted through 1 June.

DPDK 21.08 should be released on early August, in a tight schedule: http://core.dpdk.org/roadmap#dates

Please share your features roadmap.

Thanks, everyone, for allowing us to close a great 21.05 on 21/05!

DPDK Developer Spotlight: Dmitry Kozlyuk

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The DPDK community is comprised of a diverse set of active developers who are passionate about transforming the industry through open source. This blog series highlights the people who are collaborating in the trenches to transform data plane acceleration.

Name: Dmitry Kozlyuk
Title: Software Developer
Employer: BIFIT

When did you start getting into programming in general? What about data plane?
It began with C++ self-study in middle school around 2007. In 2014 I got my first networking-related job in high-frequency trading (HFT), since 2016 I’m working on a DDoS protection product based on DPDK.

 How are you involved in DPDK?
I mostly work on Windows subsystem; it’s my free-time activity.

 What intrigued you about DPDK or what prompted you to want to contribute to the project?
The product I’m working at is based on DPDK. I’d always been looking up to the project and the people building it. Then I discovered that I can be of help and become one of them.

 When did you start contributing to DPDK?
February 2020. 

 What is your favorite thing about working with DPDK, and what are you most proud of? 
The impact: DPDK is used so widely that every contribution may be valuable to someone, often to many.

What has been the most challenging part of working with DPDK?
The scale and variety of environments you have to care of and test your code for.

 What advice would you give to developers (or others) interested in joining DPDK?
Read mail discussions to learn what’s going on, what people care about, what are the best practices—then share your work just as they do.

What are other things you are interested in outside of DPDK (hobbies, fun facts, etc.)?
I teach programming at university (mpei.ru). At free time, I love reading SciFi books.

DPDK Summit APAC Receives First “Diversity & Inclusion” Event Badge

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We are thrilled to announce that our recent DPDK Summit APAC was the first Linux Foundation event to have earned a Gold Diversity & Inclusion badge from the Linux Foundation’s CHAOSS project! 

Event organizers can apply for an Event D&I  Badge for reasons of leadership, self-reflection, and self-improvement on issues critical to fostering more diverse and inclusive events. For us, this means taking conscious steps to make it easier for people of all backgrounds to participate in our events — from submitting speaking sessions to attending. 

The awarding of the CHAOSS D&I badge is an acknowledgement of DPDK’s commitment to implementing healthy Diversity and Inclusion (D&I) practices. These efforts are complementary to community-driven efforts to engage in using more inclusive language within the DPDK codebase. For this event, we were  measured on our efforts related to Speaker and Attendee Diversity & Inclusion, commitment to a specific code of conduct for all attendees, and measurement of access to the event, specifically measuring what, if any, barriers to access attendees must overcome to attend the event. Because all recent DPDK Summit events have been virtual, it has been an especially important initiative to welcome attendees from all over the world. One way we have been able to accomplish this is to offer all virtual events free of cost. 

While we are still a long way off from a fully diverse crowd, we are thrilled to have been recognized for the efforts we are making. It is so important –especially in a community as traditionally homogeneous as DPDK — that all voices be heard and welcomed. 

Big thanks to Rachel Braun and the Linux Foundation Events team for help making this a reality. 

We look forward to making even more strides towards greater diversity and wider inclusion among DPDK events in the future. 

 

 

 

DPDK adopts the C11 memory model

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By Honnappa Nagarahalli

DPDK is widely used across the technology industry to accelerate packet processing on a varied mix of platforms and architectures. However, all architectures are not created the same way and they all have differing characteristics. For frameworks such as DPDK, it is a challenge to efficiently use specific architecture features without impacting performance of other supported architectures.

One such characteristic is the memory model, which describes the behavior of accesses to shared memory by multi-processor systems. The Arm and PowerPC architectures support a weakly ordered memory model whereas x86 supports a strongly ordered memory model. Consider the following table that shows the ordering guarantees provided by these architectures for various sequences of memory operations.

As shown above, in the Arm architecture, all four possibilities of sequences of memory operations can be reordered. If an algorithm requires these memory operations to be executed (completed) in the program order, memory barriers are required to enforce the ordering. On x86, only store – load sequence can be reordered and requires a barrier to enforce the program order. The other sequences are guaranteed to execute in the program order.

However, not all algorithms need the stronger ordering guarantees. For example, take the case of a simple spinlock protecting a critical section.

The operations inside the critical section are not allowed to hoist above ‘spinlock-lock’ and sink below ‘spinlock-unlock’. But the operations above are allowed to sink below ‘spinlock-lock’ and the operations below are allowed to hoist above ‘spinlock-unlock’. In this case, protecting the critical section using locks does not require that lock and unlock functions provide full barriers. This gives more flexibility to the CPU to execute the instructions efficiently during run time. Note that this is just one example and many other algorithms have similar behaviors. The Arm architecture ‘provides load/store instructions, atomic instructions and barriers that support sinking and hoisting of memory operations in one direction [3].

In order to support such architectural differences DPDK uses abstract APIs. The rte_smp_mb/wmb/rmb APIs provide support for full memory barrier, store memory barrier and load memory barrier. APIs for atomic operations such as  rte_atomic_load/store/add/sub are also available. These APIs use full barriers and do not take any memory ordering parameter that help implement one-way barriers. Hence, it is not possible for the DPDK internal algorithms and applications to make use of the underlying CPU architecture effectively.

Exploring options

The DPDK community explored several options to solve this issue. The first option looked at relaxing the memory barriers used in the implementation of the above-mentioned APIs. It was soon realized that the type of memory ordering required depends on the algorithm and cannot be generalized. i.e., different algorithms may call the same API with different memory ordering. The second option looked at extending the existing APIs to take the memory ordering as one of the parameters while providing backward compatibility to existing APIs. This would however have resulted in writing large number of APIs to conform with the existing APIs.

Enter C11 Memory Model

The C language introduced the C11 memory model to address the above discussed differences in CPU architectures. It provides a memory model, that encompasses the behavior of widely used architectures, for multiple threads of execution to communicate with each other using shared memory. The C language supports this memory model through the atomic_xxx APIs provided in stdatomic.h. GCC and Clang compilers also provide __atomic_xxx built-ins. These APIs and built-ins allow the programmers to express the weak memory ordering inherent in their algorithms.

Several algorithms in DPDK were modified to use the C11 memory model on Arm. These changes didn’t affect the performance on x86 and at the same time, it improved the performance on weakly ordered memory model architectures like Arm. Thorough testing was done on several more algorithms to prove this further. Based on these results, the DPDK Tech Board voted unanimously to adopt the C11 memory model as the default memory model starting in the 20.08 release [4]. This means that, all the patches submitted by the DPDK community for subsequent releases should use C11 memory model. In order to support this adoption, Arm has agreed to change the existing code to use C11 memory model.

Community Discussions

The community discussed whether to use the __atomic_xxx built-ins or the atomic_xxx APIs provided via stdatomic.h. The __atomic_xxx built-ins require the memory order parameter in every built-in, requiring the programmer to make a conscious decision on the right memory order to use. They are supported by GCC, ICC and Clang compilers. The atomic_xxx APIs are not supported by compilers packaged with older versions of Linux distributions. After some debate it was decided to use the built-ins as there was no advantage in using the atomic APIs.

For x86 architecture, the __atomic_thread_fence(__ATOMIC_SEQ_CST) generates mfence instruction. DPDK implements the same barrier semantics with less overhead. Hence a decision was taken to introduce a wrapper rte_atomic_thread_fence. For x86 architecture, it calls the optimized implementation for __ATOMIC_SEQ_CST and calls __atomic_thread_fence for the rest. For rest of the architectures, it calls __atomic_thread_fence.

The community also decided to enforce this adoption using the check patch script. The script is updated to throw a warning if the patch uses the rte_smp_mb/rmb/wmb and rte_atomic_xxx APIs. All patch owners must fix such warning by using the __atomic_xxx built-ins. It is also the maintainers’ responsibility to look out for these warnings.

Current Status

Even though Arm has agreed to change the existing code to use C11 memory model, contributions from the community are highly welcome. So far 12 libraries have been updated with several more still to be updated. Several race conditions and atomicity related bugs have been identified and fixed during this process.

Conclusion

The adoption of the C11 memory model has helped DPDK community to develop robust code that performs best on all supported architectures. The community has developed a very good understanding of the C11 memory model. 

If anyone needs help in designing/coding their next algorithm using C11 memory model, please ask at dev@dpdk.org.

Acknowledgements

Special thanks to Ola Liljedahl, Philippe Robin, Ananyev Konstantin, David Christensen and David Marchand for reviewing this blog.

References

[1] https://openpowerfoundation.org/?resource_lib=power-isa-version-3-0
[2] https://software.intel.com/content/www/us/en/develop/download/intel-64-and-ia-32-architectures-sdm-volume-3a-system-programming-guide-part-1.html
[3] https://developer.arm.com/documentation/100941/0100/
[4] https://mails.dpdk.org/archives/dev/2020-April/165143.html

DPDK Release 21.02 is Now Available!

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By Thomas Monjalon from the DPDK Tech Board 

The DPDK community has issued a new release, 21.02: https://fast.dpdk.org/rel/dpdk-21.02.tar.xz

It was a light period as February releases of the 2 previous years:

  •  941 commits from 140 authors
  •  1208 files changed, 53571 insertions(+), 21946 deletions(-)

There are no plans to start a maintenance branch for 21.02. This version is ABI-compatible with 20.11.

Note 1: you may need pyelftools to compile DPDK drivers.
Note 2: a cleanup made out-of-tree drivers more difficult to compile.

Below are some new features, grouped by category.

  • Networking
    • power management for core polling single ethdev queue
    •  generic modify action in flow API
    • GENEVE TLV option in flow API
    • Marvell OCTEON TX EP net PMD
    •  Virtio PMD rework
    •  Windows support of i40e and mlx5
  • Cryptography
    • callback API for enqueue/dequeue
  • Compression
    • Mellanox compress PMD
  •  Others
    • new pmdinfogen with Windows support

More technical details in the full release notes: https://doc.dpdk.org/guides/rel_notes/release_21_02.html

There are 34 new contributors (including authors, reviewers and testers).

Welcome to Andrew Boyer, Andrii Pypchenko, Ashish Sadanandan, Barry Cao, Dana Vardi, Dapeng Yu, Fabio Pricoco, Fei Chen, Francis Kelly, Fredrik A Lindgren, George Prekas, Jacek Bułatek, Jiawei Zhu, Kiran KN, Lingyu Liu, Louis Peens, Mateusz Pacuszka, Meir Levi, Milena Olech, Murphy Yang, Nalla Pradeep, Neel Patel, Odi Assli, Paolo Valerio, Peng He, Samik Gupta, Simon Ellmann, Somalapuram Amaranath, Subhi Masri, Szymon T Cudzilo, Tyler Retzlaff, Viacheslav Galaktionov, Wenjun Wu and Yongxin Liu.

Below is the percentage of commits per employer (with authors count):

Based on Reviewed-by and Acked-by tags, the top non-PMD reviewers are:

         31     Ruifeng Wang <ruifeng.wang@arm.com>
         29     Ferruh Yigit <ferruh.yigit@intel.com>
         25     David Marchand <david.marchand@redhat.com>
         23     Maxime Coquelin <maxime.coquelin@redhat.com>
         17     Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
         16     Ori Kam <orika@nvidia.com>
         15     Jerin Jacob <jerinj@marvell.com>
         13     Konstantin Ananyev <konstantin.ananyev@intel.com>
         11     Viacheslav Ovsiienko <viacheslavo@nvidia.com>

The new features for 21.05 may be submitted until mid-March, in order to be reviewed and integrated before mid-April.

DPDK 21.05 should be released at mid-May: https://core.dpdk.org/roadmap#dates

Please share your features roadmap.

Thanks everyone, enjoy Spring Festival and Valentine’s Day, and let’s share as much love as we can.

  

On ABI Stability, v20 in review

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In DPDK 20.11, the DPDK community adopted ABI stable releases with the aim of easing the adoption of new features for DPDK users. If ABI stable releases is a new concept for you, or to simply refresh your memory, please read the previous post on Why is ABI Stability Important? The DPDK community put the policies and mechanisms in place to make ABI stability a reality from DPDK 19.11 onwards with a commitment to reviewing progress after a year. A year has now passed, so how did things go? The good news is that 100% backward compatibility was preserved through all the quarterly releases since DPDK 19.11.

100% compatibility means that a packet processing application built with DPDK 19.11, works just as well when upgraded to DPDK 20.08. This is crucially without necessitating an application rebuild, making for seamless upgrades. This is during a period when significant new features were added to DPDK, such as Cryptodev support for ChaCha20-Poly1305 AEAD for example. To really understand what DPDK ABI Stability means for a DPDK user, watch the demo …

 

https://bit.ly/33PcDFd 

The DPDK 20.11 release declares a new major ABI version v21 and begins a new period of backward compatibly with the DPDK 20.11 release. Kudos and thanks to all the maintainers and contributors whose hard work have made ABI stability a success.

Authored by: Ray Kinsella

DPDK Welcomes Microsoft

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To learn more about Microsoft, DPDK’s newest Gold member, and how they are working within the DPDK community, we sat down with Omar Cardona, Doug Stamper and Harini Ramakrishnan from the Core Networking team for a Q&A session.  Read below to see how Microsoft collaborates with DPDK. 

Can you tell us a little about your organization/department?

We are the Core Networking team in the Azure Edge + Platform (Azure E+P) group at Microsoft. Our organization has the charter to deliver platform innovation to support Microsoft Core OSes and bring services to modernize customer infrastructure. Our team is responsible for the L1-L7 networking stack including offloads, driver platform, transports, and HTTP across the cloud and edge. We are also responsible for SDN and container/Kubernetes networking. Key to our mission is a predictable, high bandwidth, low latency networking data plane that serves as the foundation for cloud and edge infrastructure and services. 

Why is your organization adopting an open source approach? 

Microsoft strongly believes in working with the open source communities on technological innovations to deliver transformational experiences. Multiple teams in our organization are contributing to and working with open source communities and standard bodies to innovate in the open, accelerating adoption and standardization. In fact, we have a sister team contributing to the Linux Kernel, and general Linux OS and tooling.  They work across Microsoft Cloud and On-Prem deployments, having a long-standing partnership with the DPDK community.

We have heard from our ecosystem partners and customers a desire in aligning Windows with Linux and Open Source on networking architecture and implementation. Towards this end, it was a natural progression for us to collaborate with the DPDK community and align our data plane investments. 

Why did you join DPDK and what sort of impact do you think DPDK has on the data plane?

Workloads today require an insatiable amount of network bandwidth with low latency performance. NICs are getting faster with 200GbE in the horizon, while single threaded performance of a CPU seems to be stagnating. Customers do not want to compromise their experience and are seamlessly moving workloads between the cloud and the edge deployments. The high packet rates of a cloud and a container world pose a significant challenge to the OS Kernel network stack, specifically for Virtual Networking and Network Function Virtualization. While the Windows network stack has evolved tremendously improving the cycles/per byte performance over the years, we are nearing the point of diminishing returns.  

DPDK successfully by-passes the limitations of the in-kernel network stack, while also providing a path to user mode processing. The ecosystem and ISVs are observing that DPDK allows them to enter a different realm of network performance, even at the cost of dedicating the hardware to the appliance.

We saw this with the MVP Windows DPDK port, back in 2017, when optimized l2fwd and l3fwd sample applications reached up to 70Mpps performance on Windows, Making networking apps scream on Windows with DPDK – YouTube. This is not possible today with native socket implementation on Windows. 

We believe that through our partnership with the DPDK community, we can bring this to more Windows users. 

  What do you see as the top benefits of being part of the DPDK community?

Significant effort has been underway over the last couple of years, to add Windows platform support to DPDK. Today, with v20.11 release, we have ~10 critical core libraries and drivers working on Windows platform. This would not have been possible without the support of our partners at Intel and Mellanox, under the guidance of the Techboard lead Thomas Monjalon. Not to forget critical contributions from DPDK end users and maintainers on memory management and stabilization. We would have likely not gotten the reach that we have today, but for the community. 

There is a long journey ahead to integrate Windows Platform support to ensure that each new version of DPDK libraries and APIs will build and run successfully on Windows (without forking) as validated by testing performed by the community lab. Monumental efforts are required to bring these solutions to work seamlessly with the Windows ecosystem. We hope that by working with the DPDK community, we can learn from the collective expertise and leverage the performance standardization that DPDK brings. We are deeply interested in enabling a kernel-bypass technology on Windows for devices and appliances ranging from IOT, to Client, to Cloud Based Servers. 

Aligning with the community on a high-performance packet processing model allows us to contribute and leverage mindshare, and co-engineer towards a common goal. 

What sort of contributions has your team made –or plans to make — to the community,ecosystem through DPDK participation?

One of the primary contributions from Microsoft has been bringing the ecosystem together to collectively consider DPDK as a viable kernel bypass technology on Windows. In addition, we have begun our contributions with the generic NetUIO driver for Windows. We have contributions in the pipeline which will bring support for applications such as testpmd and tools. This is just the beginning; we are looking forward to working with the UNH lab in standardizing testing on Windows SKUs and bringing our ability to get the most out of Windows to the community. We are experimenting with Network Virtualization for VM and Container performance, and increasingly leveraging DPDK tooling for Network performance profiling.

What do you think sets DPDK apart from other industry alliances or organizations?

DPDK brings unparalleled and extreme focus on network performance.  DPDK is very well organized, with good code structure and great documentation to simplify onboarding.  It has a sensible multi-platform strategy, feasible for Windows inclusion.  Specifically, the modularity and cohesion of the components and ease of combining the minimal necessary libraries to achieve application performance goals.

How will DPDK help your business?

Our team contributes to the multi-OS platform, foundational to operate and scale Microsoft’s businesses across Azure Cloud and Edge portfolio of products. Increasing application density and bandwidth requirements on our data plane, across Windows and Linux, necessitates an investment in a promising network stack bypass technology such as DPDK. DPDK’s user space poll-based, run-to-completion model allows for significant scaling of network performance in the face of stalled CPU speeds.

Working with the community on how DPDK lands on Windows Platform allows modernization of the network data path for future workloads.  Additionally, a common architecture increases the overall quality of the drivers and consumers, benefiting all DPDK high volume platforms.

What advice would you give to someone considering joining DPDK or getting involved in open source?

The first step would be to subscribe to the dev@dpdk.org email list and observe how the community functions. It’s good to start small and identify an area of expertise to contribute to. Something as simple as reviewing and testing incoming patches adds value. Beyond that, participating by submitting patches, contributing to tool chains, adding CI tests are all valuable ways to contribute. 

We are looking for contributions and expertise to bring DPDK Windows forward. Contribute patches under the guidelines, reference “dpdk-windows” in the email or write to dpdkwin@microsoft.com. We have a Windows working group that you can also join to learn how to help. 

What do you want to tell those members of the community that are interested in Windows Platform support?

Test the DPDK libraries on Windows and share your feedback! Head over to the getting started guide. A general roadmap has been published, however, we want to hear from the community to further influence our roadmap. Encourage everyone to participate in the survey below:

DPDK Governing Board Update – November 2020

By Blog

The DPDK Project has had an active third quarter thus far with the DPDK Userspace Summit in September, release of 20.11 release (the biggest DPDK release yet!), and the Governing Board focused on 2021 planning and budgeting during an October 13 virtual meeting. 

A release candidate (RC3)  for 20.11 went out last week, and turned out to be one of the biggest releases to date for DPDK. Notable updates include:  

We continue to seek additional DPDK reviewers and are looking for volunteers. If you are an active contributor to DPDK, we invite you to help review your fellow contributors’ patches; help us collectively improve DPDK releases

DPDK Userspace Summit

Capping off a tumultuous 2020, the DPDK community came together virtually for the  DPDK Userspace Summit, September 22-23rd. With over 550 registrants and 250 active participants from over 46 countries, the ecosystem came together for what was one of the largest DPDK Userspace Summits to date. We would like to extend a thank you to all the speakers, planning committee members, as well as and Arm for sponsoring the event.  Technical Presentations and videos are available in the event archive: https://www.dpdk.org/event/dpdk-userspace-summit/ 

Happy 10 years, DPDK!

DPDK project celebrated it’s 10 year anniversary during the virtual summit, marking the occasion with a new celebratory webpage, with excerpts and pictures from across the community: https://www.dpdk.org/10th-anniversary/ 

Please join us in also recognizing this year’s recipients of the 2020 Community Awards. https://www.dpdk.org/blog/2020/09/27/dpdk-community-awards-recognize-development-excellence/ 

By the Numbers

Looking back at the year, we have a lot to be proud of as a community: 

  • 2,086 Commits, 199 Authors, 18 Repositories
  • Releases: 
  • Membership Revenue saw a 14% increase over 2019
  • Events: DPDK virtual userspace 570 registered, 250 active participants
  • Community Lab testing coverage has expanded, and exceeded the original target set by the Testing Working Group. 
  • DPDK website pageviews: 36,500 (over past 90 days)
  • Publication of the DPDK White paper and video series
  • Twitter followers over 1060+

Other Notable Updates

Upcoming Events: With the prevailing impact of the global pandemic, DPDK continues to monitor and assess the viability of hosting an in person gathering; as of today, we have moved to a virtual event calendar and anticipate our next virtual gathering towards the end of Q1, 2021. Look forward to an event and CFP announcement soon. 

Budget: The Board has updated the budget to reflect our real-time changes as a result of the impact of COVID-19 and is currently discussing 2021 budget priorities and alignment. We will provide an update once the preliminary budget has been made. 

Lab: A sub-team has been working with the DPDK Community Lab team, including UNH-IOL, to expand the testing coverage provided by the Community Lab. We are happy to report that under the guidance of the Technical Steering Committee, the Testing Group has exceeded their targeted testing coverage goals of 40%, with over 56% Functional test coverage in the community lab.  The Community Lab team continues to refine its practices and plans to expand in the coming months. 

Member Outreach: No changes to membership this quarter.  If you have any suggestions for companies or individuals that we should reach out to, please let us know.

 Thank you for your continued engagement with the DPDK community! We hope everyone is staying healthy and keeping busy during these uncertain times.

DPDK Issues 20.11, Most Robust DPDK Release Ever!

By Announcements, Blog

A new major DPDK release is now available: https://fast.dpdk.org/rel/dpdk-20.11.tar.xz

Our Thanksgiving gift to the ecosystem is the biggest DPDK release ever, with:

  •     2195 commits from 214 authors
  •     2665 files changed, 269546 insertions(+), 107426 deletions(-)

The branch 20.11 should be supported for at least two years, making it recommended for system integration and deployment. The maintainer of this new LTS is Kevin Traynor.

The new major ABI version is 21. The next releases 21.02, 21.05 and 21.08 will be ABI compatible with 20.11.

Below are some new features, grouped by category.

  • General
    • mbuf dynamic area increased from 16 to 36 bytes
    • ring zero cop
    • SIMD bitwidth limit API
    • Windows PCI netuio
    • moved igb_uio to dpdk-kmods/linux
    • removed Python 2 support
    • removed Make support
  • Networking
    •  FEC AP
    • Rx buffer split
    • thread safety in flow API
    • shared action in flow API
    •  flow sampling and mirroring
    • tunnel offload API
    •  multi-port hairpin
    • Solarflare EF100 architecture
    • Wangxun txgbe driver
    • vhost-vDPA backend in virtio-user
    • removed vhost dequeue zero-copy
    •  removed legacy ethdev filtering
    • SWX pipeline aligned with P4
  • Baseband
    • Intel ACC100 driver
  • Cryptography
    • raw datapath API
    • Broadcom BCMFS symmetric crypto driver
  • RegEx
    • Marvell OCTEON TX2 regex driver
  • Others
    • Intel DLB/DLB2 drivers
    • Intel DSA support in IOAT driver

More details in the release notes:https://doc.dpdk.org/guides/rel_notes/release_20_11.html

There are 64 new contributors (including authors, reviewers and testers). Welcome to Aidan Goddard, Amit Bernstein, Andrey Vesnovaty, Artur Rojek, Benoît Ganne, Brandon Lo, Brian Johnson, Brian Poole, Christophe Grosse, Churchill Khangar, Conor Walsh, David Liu, Dawid Lukwinski, Diogo Behrens, Dongdong Liu, Franck Lenormand, Galazka Krzysztof, Guoyang Zhou, Haggai Eran, Harshitha Ramamurthy, Ibtisam Tariq, Ido Segev, Jay Jayatheerthan, Jiawen Wu, Jie Zhou, John Alexander, Julien Massonneau, Jørgen Østergaard Sloth, Khoa To, Li Zhang, Lingli Chen, Liu Tianjiao, Maciej Rabeda, Marcel Cornu, Mike Ximing Chen, Muthurajan Jayakumar, Nan Chen, Nick Connolly, Norbert Ciosek, Omkar Maslekar, Padraig Connolly, Piotr Bronowski, Przemyslaw Ciesielski, Qin Sun, Radha Mohan Chintakuntla, Rani Sharoni, Raveendra Padasalagi, Robin Zhang, RongQing Li, Shay Amir, Steve Yang, Steven Lariau, Tom Rix, Venkata Suresh Kumar P, Vijay Kumar Srivastava, Vikas Gupta, Vimal Chungath, Vipul Ashri, Wei Huang, Wei Ling, Weqaar Janjua, Yi Yang, Yogesh Jangra and Zhenghua Zhou.

Below is the breakout of commits by employer:

     Based on Reviewed-by and Acked-by tags, the top non-PMD reviewers are:

        128     Ferruh Yigit <ferruh.yigit@intel.com>
         68     Bruce Richardson <bruce.richardson@intel.com>
         63     Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
         62     David Marchand <david.marchand@redhat.com>
         53     Ruifeng Wang <ruifeng.wang@arm.com>
         40     Konstantin Ananyev <konstantin.ananyev@intel.com>
         38     Ajit Khaparde <ajit.khaparde@broadcom.com>
         37     Ori Kam <orika@nvidia.com>
         33     Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>

New features for 21.02 may be submitted during the next 3 weeks, in order to be reviewed and integrated before mid-January. DPDK 21.02 should be small in order to release in early February:  https://core.dpdk.org/roadmap#dates

Please share your roadmap.

Thanks to everyone who helped make this release happen – what a great way to wrap up 2020!