Message ID | 1447407013-6986-1-git-send-email-tkiely@brocade.com (mailing list archive) |
---|---|
State | Superseded, archived |
Delegated to: | Bruce Richardson |
Headers |
Return-Path: <dev-bounces@dpdk.org> X-Original-To: patchwork@dpdk.org Delivered-To: patchwork@dpdk.org Received: from [92.243.14.124] (localhost [IPv6:::1]) by dpdk.org (Postfix) with ESMTP id 9F42B93B8; Fri, 13 Nov 2015 10:30:55 +0100 (CET) Received: from mx0b-000f0801.pphosted.com (mx0b-000f0801.pphosted.com [67.231.152.113]) by dpdk.org (Postfix) with ESMTP id 07F6C93B4 for <dev@dpdk.org>; Fri, 13 Nov 2015 10:30:53 +0100 (CET) Received: from pps.filterd (m0048192.ppops.net [127.0.0.1]) by mx0b-000f0801.pphosted.com (8.15.0.59/8.15.0.59) with SMTP id tAD99Ms0020370 for <dev@dpdk.org>; Fri, 13 Nov 2015 01:30:53 -0800 Received: from brmwp-exmb11.corp.brocade.com ([208.47.132.227]) by mx0b-000f0801.pphosted.com with ESMTP id 1y53251bv5-1 (version=TLSv1/SSLv3 cipher=AES256-SHA bits=256 verify=NOT) for <dev@dpdk.org>; Fri, 13 Nov 2015 01:30:53 -0800 Received: from EMEAWP-EXMB12.corp.brocade.com (172.29.11.86) by BRMWP-EXMB11.corp.brocade.com (172.16.59.77) with Microsoft SMTP Server (TLS) id 15.0.1104.5; Fri, 13 Nov 2015 02:30:51 -0700 Received: from BRA-19P4P12.brocade.com (10.252.48.12) by EMEAWP-EXMB12.corp.brocade.com (172.29.11.86) with Microsoft SMTP Server (TLS) id 15.0.1104.5; Fri, 13 Nov 2015 10:30:48 +0100 From: Tom Kiely <tkiely@brocade.com> To: <dev@dpdk.org> Date: Fri, 13 Nov 2015 09:30:13 +0000 Message-ID: <1447407013-6986-1-git-send-email-tkiely@brocade.com> X-Mailer: git-send-email 1.7.10.4 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.252.48.12] X-ClientProxiedBy: hq1wp-excas14.corp.brocade.com (10.70.38.103) To EMEAWP-EXMB12.corp.brocade.com (172.29.11.86) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.15.21, 1.0.33, 0.0.0000 definitions=2015-11-13_09:2015-11-12, 2015-11-13, 1970-01-01 signatures=0 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 suspectscore=3 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=7.0.1-1508030000 definitions=main-1511130153 Subject: [dpdk-dev] [PATCH] virtio: fix rx ring descriptor starvation X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK <dev.dpdk.org> List-Unsubscribe: <http://dpdk.org/ml/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://dpdk.org/ml/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <http://dpdk.org/ml/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> Errors-To: dev-bounces@dpdk.org Sender: "dev" <dev-bounces@dpdk.org> |
Commit Message
Tom Kiely
Nov. 13, 2015, 9:30 a.m. UTC
If all rx descriptors are processed while transient
mbuf exhaustion is present, the rx ring ends up with
no available descriptors. Thus no packets are received
on that ring. Since descriptor refill is performed post
rx descriptor processing, in this case no refill is
ever subsequently performed resulting in permanent rx
traffic drop.
Signed-off-by: Tom Kiely <tkiely@brocade.com>
---
drivers/net/virtio/virtio_rxtx.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
Comments
Any review, please? 2015-11-13 09:30, Tom Kiely: > If all rx descriptors are processed while transient > mbuf exhaustion is present, the rx ring ends up with > no available descriptors. Thus no packets are received > on that ring. Since descriptor refill is performed post > rx descriptor processing, in this case no refill is > ever subsequently performed resulting in permanent rx > traffic drop. > > Signed-off-by: Tom Kiely <tkiely@brocade.com>
On Tue, Nov 24, 2015 at 10:20:22PM +0100, Thomas Monjalon wrote: > Any review, please? Huawei, would you review it? Sorry that I've not read too much code about virtio PMD driver yet. --yliu > 2015-11-13 09:30, Tom Kiely: > > If all rx descriptors are processed while transient > > mbuf exhaustion is present, the rx ring ends up with > > no available descriptors. Thus no packets are received > > on that ring. Since descriptor refill is performed post > > rx descriptor processing, in this case no refill is > > ever subsequently performed resulting in permanent rx > > traffic drop. > > > > Signed-off-by: Tom Kiely <tkiely@brocade.com>
On 11/25/2015 9:47 AM, Yuanhan Liu wrote: > On Tue, Nov 24, 2015 at 10:20:22PM +0100, Thomas Monjalon wrote: >> Any review, please? > Huawei, would you review it? Sorry that I've not read too much > code about virtio PMD driver yet. Np. will do it by end of this week. > > --yliu > > >> 2015-11-13 09:30, Tom Kiely: >>> If all rx descriptors are processed while transient >>> mbuf exhaustion is present, the rx ring ends up with >>> no available descriptors. Thus no packets are received >>> on that ring. Since descriptor refill is performed post >>> rx descriptor processing, in this case no refill is >>> ever subsequently performed resulting in permanent rx >>> traffic drop. >>> >>> Signed-off-by: Tom Kiely <tkiely@brocade.com>
On 11/13/2015 5:33 PM, Tom Kiely wrote: > If all rx descriptors are processed while transient > mbuf exhaustion is present, the rx ring ends up with > no available descriptors. Thus no packets are received > on that ring. Since descriptor refill is performed post > rx descriptor processing, in this case no refill is > ever subsequently performed resulting in permanent rx > traffic drop. > > Signed-off-by: Tom Kiely <tkiely@brocade.com> > --- > drivers/net/virtio/virtio_rxtx.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c > index 5770fa2..a95e234 100644 > --- a/drivers/net/virtio/virtio_rxtx.c > +++ b/drivers/net/virtio/virtio_rxtx.c > @@ -586,7 +586,8 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t nb_pkts) > if (likely(num > DESC_PER_CACHELINE)) > num = num - ((rxvq->vq_used_cons_idx + num) % DESC_PER_CACHELINE); > > - if (num == 0) > + /* Refill free descriptors even if no pkts recvd */ > + if (num == 0 && virtqueue_full(rxvq)) Should the return condition be that no used buffers and we have avail descs in avail ring, i.e, num == 0 && rxvq->vq_free_cnt != rxvq->vq_nentries rather than num == 0 && rxvq->vq_free_cnt == 0 ? > return 0; > > num = virtqueue_dequeue_burst_rx(rxvq, rcv_pkts, len, num); > @@ -683,7 +684,8 @@ virtio_recv_mergeable_pkts(void *rx_queue, > > virtio_rmb(); > > - if (nb_used == 0) > + /* Refill free descriptors even if no pkts recvd */ > + if (nb_used == 0 && virtqueue_full(rxvq)) > return 0; > > PMD_RX_LOG(DEBUG, "used:%d\n", nb_used);
On 11/26/2015 1:33 AM, Xie, Huawei wrote: > On 11/13/2015 5:33 PM, Tom Kiely wrote: >> If all rx descriptors are processed while transient >> mbuf exhaustion is present, the rx ring ends up with >> no available descriptors. Thus no packets are received >> on that ring. Since descriptor refill is performed post >> rx descriptor processing, in this case no refill is >> ever subsequently performed resulting in permanent rx >> traffic drop. >> >> Signed-off-by: Tom Kiely <tkiely@brocade.com> >> --- >> drivers/net/virtio/virtio_rxtx.c | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c >> index 5770fa2..a95e234 100644 >> --- a/drivers/net/virtio/virtio_rxtx.c >> +++ b/drivers/net/virtio/virtio_rxtx.c >> @@ -586,7 +586,8 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t nb_pkts) >> if (likely(num > DESC_PER_CACHELINE)) >> num = num - ((rxvq->vq_used_cons_idx + num) % DESC_PER_CACHELINE); >> >> - if (num == 0) >> + /* Refill free descriptors even if no pkts recvd */ >> + if (num == 0 && virtqueue_full(rxvq)) > Should the return condition be that no used buffers and we have avail > descs in avail ring, i.e, > num == 0 && rxvq->vq_free_cnt != rxvq->vq_nentries > > rather than > num == 0 && rxvq->vq_free_cnt == 0 > ? Tom: Any further progress? >> return 0; >> >> num = virtqueue_dequeue_burst_rx(rxvq, rcv_pkts, len, num); >> @@ -683,7 +684,8 @@ virtio_recv_mergeable_pkts(void *rx_queue, >> >> virtio_rmb(); >> >> - if (nb_used == 0) >> + /* Refill free descriptors even if no pkts recvd */ >> + if (nb_used == 0 && virtqueue_full(rxvq)) >> return 0; >> >> PMD_RX_LOG(DEBUG, "used:%d\n", nb_used); >
Hi, Sorry for the delay. I have been occupied on another critical issue. I'll look at this today. Tom On 12/17/2015 04:47 AM, Xie, Huawei wrote: > On 11/26/2015 1:33 AM, Xie, Huawei wrote: >> On 11/13/2015 5:33 PM, Tom Kiely wrote: >>> If all rx descriptors are processed while transient >>> mbuf exhaustion is present, the rx ring ends up with >>> no available descriptors. Thus no packets are received >>> on that ring. Since descriptor refill is performed post >>> rx descriptor processing, in this case no refill is >>> ever subsequently performed resulting in permanent rx >>> traffic drop. >>> >>> Signed-off-by: Tom Kiely <tkiely@brocade.com> >>> --- >>> drivers/net/virtio/virtio_rxtx.c | 6 ++++-- >>> 1 file changed, 4 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c >>> index 5770fa2..a95e234 100644 >>> --- a/drivers/net/virtio/virtio_rxtx.c >>> +++ b/drivers/net/virtio/virtio_rxtx.c >>> @@ -586,7 +586,8 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t nb_pkts) >>> if (likely(num > DESC_PER_CACHELINE)) >>> num = num - ((rxvq->vq_used_cons_idx + num) % DESC_PER_CACHELINE); >>> >>> - if (num == 0) >>> + /* Refill free descriptors even if no pkts recvd */ >>> + if (num == 0 && virtqueue_full(rxvq)) >> Should the return condition be that no used buffers and we have avail >> descs in avail ring, i.e, >> num == 0 && rxvq->vq_free_cnt != rxvq->vq_nentries >> >> rather than >> num == 0 && rxvq->vq_free_cnt == 0 >> ? > Tom: > Any further progress? >>> return 0; >>> >>> num = virtqueue_dequeue_burst_rx(rxvq, rcv_pkts, len, num); >>> @@ -683,7 +684,8 @@ virtio_recv_mergeable_pkts(void *rx_queue, >>> >>> virtio_rmb(); >>> >>> - if (nb_used == 0) >>> + /* Refill free descriptors even if no pkts recvd */ >>> + if (nb_used == 0 && virtqueue_full(rxvq)) >>> return 0; >>> >>> PMD_RX_LOG(DEBUG, "used:%d\n", nb_used);
On 11/25/2015 05:32 PM, Xie, Huawei wrote: > On 11/13/2015 5:33 PM, Tom Kiely wrote: >> If all rx descriptors are processed while transient >> mbuf exhaustion is present, the rx ring ends up with >> no available descriptors. Thus no packets are received >> on that ring. Since descriptor refill is performed post >> rx descriptor processing, in this case no refill is >> ever subsequently performed resulting in permanent rx >> traffic drop. >> >> Signed-off-by: Tom Kiely <tkiely@brocade.com> >> --- >> drivers/net/virtio/virtio_rxtx.c | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c >> index 5770fa2..a95e234 100644 >> --- a/drivers/net/virtio/virtio_rxtx.c >> +++ b/drivers/net/virtio/virtio_rxtx.c >> @@ -586,7 +586,8 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t nb_pkts) >> if (likely(num > DESC_PER_CACHELINE)) >> num = num - ((rxvq->vq_used_cons_idx + num) % DESC_PER_CACHELINE); >> >> - if (num == 0) >> + /* Refill free descriptors even if no pkts recvd */ >> + if (num == 0 && virtqueue_full(rxvq)) > Should the return condition be that no used buffers and we have avail > descs in avail ring, i.e, > num == 0 && rxvq->vq_free_cnt != rxvq->vq_nentries > > rather than > num == 0 && rxvq->vq_free_cnt == 0 Yes we could do that but I don't see a good reason to wait until the vq_free_cnt == vq_nentries before attempting the refill. The existing code will attempt refill even if only 1 packet was received and the free count is small. To me it seems safer to extend that to try refill even if no packet was received but the free count is non-zero. Tom >> return 0; >> >> num = virtqueue_dequeue_burst_rx(rxvq, rcv_pkts, len, num); >> @@ -683,7 +684,8 @@ virtio_recv_mergeable_pkts(void *rx_queue, >> >> virtio_rmb(); >> >> - if (nb_used == 0) >> + /* Refill free descriptors even if no pkts recvd */ >> + if (nb_used == 0 && virtqueue_full(rxvq)) >> return 0; >> >> PMD_RX_LOG(DEBUG, "used:%d\n", nb_used);
On 12/17/2015 7:18 PM, Tom Kiely wrote: > > > On 11/25/2015 05:32 PM, Xie, Huawei wrote: >> On 11/13/2015 5:33 PM, Tom Kiely wrote: >>> If all rx descriptors are processed while transient >>> mbuf exhaustion is present, the rx ring ends up with >>> no available descriptors. Thus no packets are received >>> on that ring. Since descriptor refill is performed post >>> rx descriptor processing, in this case no refill is >>> ever subsequently performed resulting in permanent rx >>> traffic drop. >>> >>> Signed-off-by: Tom Kiely <tkiely@brocade.com> >>> --- >>> drivers/net/virtio/virtio_rxtx.c | 6 ++++-- >>> 1 file changed, 4 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/net/virtio/virtio_rxtx.c >>> b/drivers/net/virtio/virtio_rxtx.c >>> index 5770fa2..a95e234 100644 >>> --- a/drivers/net/virtio/virtio_rxtx.c >>> +++ b/drivers/net/virtio/virtio_rxtx.c >>> @@ -586,7 +586,8 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf >>> **rx_pkts, uint16_t nb_pkts) >>> if (likely(num > DESC_PER_CACHELINE)) >>> num = num - ((rxvq->vq_used_cons_idx + num) % >>> DESC_PER_CACHELINE); >>> - if (num == 0) >>> + /* Refill free descriptors even if no pkts recvd */ >>> + if (num == 0 && virtqueue_full(rxvq)) >> Should the return condition be that no used buffers and we have avail >> descs in avail ring, i.e, >> num == 0 && rxvq->vq_free_cnt != rxvq->vq_nentries >> >> rather than >> num == 0 && rxvq->vq_free_cnt == 0 > Yes we could do that but I don't see a good reason to wait until the > vq_free_cnt == vq_nentries > before attempting the refill. The existing code will attempt refill > even if only 1 packet was received > and the free count is small. To me it seems safer to extend that to > try refill even if no packet was received > but the free count is non-zero. The existing code attempt to refill only if 1 packet was received. If we want to refill even no packet was received, then the strict condition should be num == 0 && rxvq->vq_free_cnt != rxvq->vq_nentries The safer condition, what you want to use, should be num == 0 && !virtqueue_full(...) rather than num == 0 && virtqueue_full(...) We could simplify things a bit, just remove this check, if the following receiving code already takes care of the "num == 0" condition. I find virtqueue_full is confusing, maybe we could change it to some other meaningful name. > > Tom > >>> return 0; >>> num = virtqueue_dequeue_burst_rx(rxvq, rcv_pkts, len, num); >>> @@ -683,7 +684,8 @@ virtio_recv_mergeable_pkts(void *rx_queue, >>> virtio_rmb(); >>> - if (nb_used == 0) >>> + /* Refill free descriptors even if no pkts recvd */ >>> + if (nb_used == 0 && virtqueue_full(rxvq)) >>> return 0; >>> PMD_RX_LOG(DEBUG, "used:%d\n", nb_used); > >
On Tue, Jan 05, 2016 at 07:13:04AM +0000, Xie, Huawei wrote: > On 12/17/2015 7:18 PM, Tom Kiely wrote: > > > > > > On 11/25/2015 05:32 PM, Xie, Huawei wrote: > >> On 11/13/2015 5:33 PM, Tom Kiely wrote: > >>> If all rx descriptors are processed while transient > >>> mbuf exhaustion is present, the rx ring ends up with > >>> no available descriptors. Thus no packets are received > >>> on that ring. Since descriptor refill is performed post > >>> rx descriptor processing, in this case no refill is > >>> ever subsequently performed resulting in permanent rx > >>> traffic drop. > >>> > >>> Signed-off-by: Tom Kiely <tkiely@brocade.com> > >>> --- > >>> drivers/net/virtio/virtio_rxtx.c | 6 ++++-- > >>> 1 file changed, 4 insertions(+), 2 deletions(-) > >>> > >>> diff --git a/drivers/net/virtio/virtio_rxtx.c > >>> b/drivers/net/virtio/virtio_rxtx.c > >>> index 5770fa2..a95e234 100644 > >>> --- a/drivers/net/virtio/virtio_rxtx.c > >>> +++ b/drivers/net/virtio/virtio_rxtx.c > >>> @@ -586,7 +586,8 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf > >>> **rx_pkts, uint16_t nb_pkts) > >>> if (likely(num > DESC_PER_CACHELINE)) > >>> num = num - ((rxvq->vq_used_cons_idx + num) % > >>> DESC_PER_CACHELINE); > >>> - if (num == 0) > >>> + /* Refill free descriptors even if no pkts recvd */ > >>> + if (num == 0 && virtqueue_full(rxvq)) > >> Should the return condition be that no used buffers and we have avail > >> descs in avail ring, i.e, > >> num == 0 && rxvq->vq_free_cnt != rxvq->vq_nentries > >> > >> rather than > >> num == 0 && rxvq->vq_free_cnt == 0 > > Yes we could do that but I don't see a good reason to wait until the > > vq_free_cnt == vq_nentries > > before attempting the refill. The existing code will attempt refill > > even if only 1 packet was received > > and the free count is small. To me it seems safer to extend that to > > try refill even if no packet was received > > but the free count is non-zero. > The existing code attempt to refill only if 1 packet was received. > > If we want to refill even no packet was received, then the strict > condition should be > num == 0 && rxvq->vq_free_cnt != rxvq->vq_nentries > > The safer condition, what you want to use, should be > num == 0 && !virtqueue_full(...) > rather than > num == 0 && virtqueue_full(...) > > We could simplify things a bit, just remove this check, if the following > receiving code already takes care of the "num == 0" condition. > > I find virtqueue_full is confusing, maybe we could change it to some > other meaningful name. > > > > > Tom > > Ping. Tom and Huawei, what is the status of this patch? Will there be a V2? /Bruce
On Tue, Jan 5, 2016 at 2:13 AM, Xie, Huawei <huawei.xie@intel.com> wrote: > On 12/17/2015 7:18 PM, Tom Kiely wrote: >> >> >> On 11/25/2015 05:32 PM, Xie, Huawei wrote: >>> On 11/13/2015 5:33 PM, Tom Kiely wrote: >>>> If all rx descriptors are processed while transient >>>> mbuf exhaustion is present, the rx ring ends up with >>>> no available descriptors. Thus no packets are received >>>> on that ring. Since descriptor refill is performed post >>>> rx descriptor processing, in this case no refill is >>>> ever subsequently performed resulting in permanent rx >>>> traffic drop. >>>> >>>> Signed-off-by: Tom Kiely <tkiely@brocade.com> >>>> --- >>>> drivers/net/virtio/virtio_rxtx.c | 6 ++++-- >>>> 1 file changed, 4 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/drivers/net/virtio/virtio_rxtx.c >>>> b/drivers/net/virtio/virtio_rxtx.c >>>> index 5770fa2..a95e234 100644 >>>> --- a/drivers/net/virtio/virtio_rxtx.c >>>> +++ b/drivers/net/virtio/virtio_rxtx.c >>>> @@ -586,7 +586,8 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf >>>> **rx_pkts, uint16_t nb_pkts) >>>> if (likely(num > DESC_PER_CACHELINE)) >>>> num = num - ((rxvq->vq_used_cons_idx + num) % >>>> DESC_PER_CACHELINE); >>>> - if (num == 0) >>>> + /* Refill free descriptors even if no pkts recvd */ >>>> + if (num == 0 && virtqueue_full(rxvq)) >>> Should the return condition be that no used buffers and we have avail >>> descs in avail ring, i.e, >>> num == 0 && rxvq->vq_free_cnt != rxvq->vq_nentries >>> >>> rather than >>> num == 0 && rxvq->vq_free_cnt == 0 >> Yes we could do that but I don't see a good reason to wait until the >> vq_free_cnt == vq_nentries >> before attempting the refill. The existing code will attempt refill >> even if only 1 packet was received >> and the free count is small. To me it seems safer to extend that to >> try refill even if no packet was received >> but the free count is non-zero. > The existing code attempt to refill only if 1 packet was received. > > If we want to refill even no packet was received, then the strict > condition should be > num == 0 && rxvq->vq_free_cnt != rxvq->vq_nentries > > The safer condition, what you want to use, should be > num == 0 && !virtqueue_full(...) > rather than > num == 0 && virtqueue_full(...) > > We could simplify things a bit, just remove this check, if the following > receiving code already takes care of the "num == 0" condition. > FWIW, I fixed this issue myself by just removing the if(num == 0) checks entirely. I didn't see any benefit in short-circuiting a loop which pretty much does nothing anyway when num == 0. Further, we only hit this case when there's no packets to receive, which means there's probably a few cycles to spare. This is even simpler. > I find virtqueue_full is confusing, maybe we could change it to some > other meaningful name. > >> >> Tom >> >>>> return 0; >>>> num = virtqueue_dequeue_burst_rx(rxvq, rcv_pkts, len, num); >>>> @@ -683,7 +684,8 @@ virtio_recv_mergeable_pkts(void *rx_queue, >>>> virtio_rmb(); >>>> - if (nb_used == 0) >>>> + /* Refill free descriptors even if no pkts recvd */ >>>> + if (nb_used == 0 && virtqueue_full(rxvq)) >>>> return 0; >>>> PMD_RX_LOG(DEBUG, "used:%d\n", nb_used); >> >> >
Hi, Sorry I missed the last few messages until now. I'm happy with just removing the "if". Kyle, when you say you fixed it, do you mean that you will push the patch or have already done so ? Thanks, Tom On 02/18/2016 02:03 PM, Kyle Larose wrote: > On Tue, Jan 5, 2016 at 2:13 AM, Xie, Huawei <huawei.xie@intel.com> wrote: >> On 12/17/2015 7:18 PM, Tom Kiely wrote: >>> >>> On 11/25/2015 05:32 PM, Xie, Huawei wrote: >>>> On 11/13/2015 5:33 PM, Tom Kiely wrote: >>>>> If all rx descriptors are processed while transient >>>>> mbuf exhaustion is present, the rx ring ends up with >>>>> no available descriptors. Thus no packets are received >>>>> on that ring. Since descriptor refill is performed post >>>>> rx descriptor processing, in this case no refill is >>>>> ever subsequently performed resulting in permanent rx >>>>> traffic drop. >>>>> >>>>> Signed-off-by: Tom Kiely <tkiely@brocade.com> >>>>> --- >>>>> drivers/net/virtio/virtio_rxtx.c | 6 ++++-- >>>>> 1 file changed, 4 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/drivers/net/virtio/virtio_rxtx.c >>>>> b/drivers/net/virtio/virtio_rxtx.c >>>>> index 5770fa2..a95e234 100644 >>>>> --- a/drivers/net/virtio/virtio_rxtx.c >>>>> +++ b/drivers/net/virtio/virtio_rxtx.c >>>>> @@ -586,7 +586,8 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf >>>>> **rx_pkts, uint16_t nb_pkts) >>>>> if (likely(num > DESC_PER_CACHELINE)) >>>>> num = num - ((rxvq->vq_used_cons_idx + num) % >>>>> DESC_PER_CACHELINE); >>>>> - if (num == 0) >>>>> + /* Refill free descriptors even if no pkts recvd */ >>>>> + if (num == 0 && virtqueue_full(rxvq)) >>>> Should the return condition be that no used buffers and we have avail >>>> descs in avail ring, i.e, >>>> num == 0 && rxvq->vq_free_cnt != rxvq->vq_nentries >>>> >>>> rather than >>>> num == 0 && rxvq->vq_free_cnt == 0 >>> Yes we could do that but I don't see a good reason to wait until the >>> vq_free_cnt == vq_nentries >>> before attempting the refill. The existing code will attempt refill >>> even if only 1 packet was received >>> and the free count is small. To me it seems safer to extend that to >>> try refill even if no packet was received >>> but the free count is non-zero. >> The existing code attempt to refill only if 1 packet was received. >> >> If we want to refill even no packet was received, then the strict >> condition should be >> num == 0 && rxvq->vq_free_cnt != rxvq->vq_nentries >> >> The safer condition, what you want to use, should be >> num == 0 && !virtqueue_full(...) >> rather than >> num == 0 && virtqueue_full(...) >> >> We could simplify things a bit, just remove this check, if the following >> receiving code already takes care of the "num == 0" condition. >> > FWIW, I fixed this issue myself by just removing the if(num == 0) > checks entirely. I didn't see any benefit in short-circuiting a loop > which pretty much does nothing anyway when num == 0. Further, we only > hit this case when there's no packets to receive, which means there's > probably a few cycles to spare. This is even simpler. > >> I find virtqueue_full is confusing, maybe we could change it to some >> other meaningful name. >> >>> Tom >>> >>>>> return 0; >>>>> num = virtqueue_dequeue_burst_rx(rxvq, rcv_pkts, len, num); >>>>> @@ -683,7 +684,8 @@ virtio_recv_mergeable_pkts(void *rx_queue, >>>>> virtio_rmb(); >>>>> - if (nb_used == 0) >>>>> + /* Refill free descriptors even if no pkts recvd */ >>>>> + if (nb_used == 0 && virtqueue_full(rxvq)) >>>>> return 0; >>>>> PMD_RX_LOG(DEBUG, "used:%d\n", nb_used); >>>
On 2/23/2016 12:23 AM, Tom Kiely wrote: > Hi, > Sorry I missed the last few messages until now. I'm happy with > just removing the "if". Kyle, when you say you fixed it, do you mean > that you will push the patch or have already done so ? > Thanks, > Tom > > On 02/18/2016 02:03 PM, Kyle Larose wrote: >> On Tue, Jan 5, 2016 at 2:13 AM, Xie, Huawei <huawei.xie@intel.com> >> wrote: >>> On 12/17/2015 7:18 PM, Tom Kiely wrote: >>>> >>>> On 11/25/2015 05:32 PM, Xie, Huawei wrote: >>>>> On 11/13/2015 5:33 PM, Tom Kiely wrote: >>>>>> If all rx descriptors are processed while transient >>>>>> mbuf exhaustion is present, the rx ring ends up with >>>>>> no available descriptors. Thus no packets are received >>>>>> on that ring. Since descriptor refill is performed post >>>>>> rx descriptor processing, in this case no refill is >>>>>> ever subsequently performed resulting in permanent rx >>>>>> traffic drop. >>>>>> >>>>>> Signed-off-by: Tom Kiely <tkiely@brocade.com> >>>>>> --- >>>>>> drivers/net/virtio/virtio_rxtx.c | 6 ++++-- >>>>>> 1 file changed, 4 insertions(+), 2 deletions(-) >>>>>> >>>>>> diff --git a/drivers/net/virtio/virtio_rxtx.c >>>>>> b/drivers/net/virtio/virtio_rxtx.c >>>>>> index 5770fa2..a95e234 100644 >>>>>> --- a/drivers/net/virtio/virtio_rxtx.c >>>>>> +++ b/drivers/net/virtio/virtio_rxtx.c >>>>>> @@ -586,7 +586,8 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf >>>>>> **rx_pkts, uint16_t nb_pkts) >>>>>> if (likely(num > DESC_PER_CACHELINE)) >>>>>> num = num - ((rxvq->vq_used_cons_idx + num) % >>>>>> DESC_PER_CACHELINE); >>>>>> - if (num == 0) >>>>>> + /* Refill free descriptors even if no pkts recvd */ >>>>>> + if (num == 0 && virtqueue_full(rxvq)) >>>>> Should the return condition be that no used buffers and we have avail >>>>> descs in avail ring, i.e, >>>>> num == 0 && rxvq->vq_free_cnt != rxvq->vq_nentries >>>>> >>>>> rather than >>>>> num == 0 && rxvq->vq_free_cnt == 0 >>>> Yes we could do that but I don't see a good reason to wait until the >>>> vq_free_cnt == vq_nentries >>>> before attempting the refill. The existing code will attempt refill >>>> even if only 1 packet was received >>>> and the free count is small. To me it seems safer to extend that to >>>> try refill even if no packet was received >>>> but the free count is non-zero. >>> The existing code attempt to refill only if 1 packet was received. >>> >>> If we want to refill even no packet was received, then the strict >>> condition should be >>> num == 0 && rxvq->vq_free_cnt != rxvq->vq_nentries >>> >>> The safer condition, what you want to use, should be >>> num == 0 && !virtqueue_full(...) >>> rather than >>> num == 0 && virtqueue_full(...) >>> >>> We could simplify things a bit, just remove this check, if the >>> following >>> receiving code already takes care of the "num == 0" condition. >>> >> FWIW, I fixed this issue myself by just removing the if(num == 0) >> checks entirely. I didn't see any benefit in short-circuiting a loop >> which pretty much does nothing anyway when num == 0. Further, we only >> hit this case when there's no packets to receive, which means there's >> probably a few cycles to spare. This is even simpler. Yes, as i said, that is the simplest fix. >> >>> I find virtqueue_full is confusing, maybe we could change it to some >>> other meaningful name. >>> >>>> Tom >>>> >>>>>> return 0; >>>>>> num = virtqueue_dequeue_burst_rx(rxvq, rcv_pkts, len, num); >>>>>> @@ -683,7 +684,8 @@ virtio_recv_mergeable_pkts(void *rx_queue, >>>>>> virtio_rmb(); >>>>>> - if (nb_used == 0) >>>>>> + /* Refill free descriptors even if no pkts recvd */ >>>>>> + if (nb_used == 0 && virtqueue_full(rxvq)) >>>>>> return 0; >>>>>> PMD_RX_LOG(DEBUG, "used:%d\n", nb_used); >>>> > >
On 2/23/2016 12:23 AM, Tom Kiely wrote: > Hi, > Sorry I missed the last few messages until now. I'm happy with > just removing the "if". Kyle, when you say you fixed it, do you mean > that you will push the patch or have already done so ? > Thanks, > Tom Could you please send the patch?
Sure. Tom On 03/04/2016 06:16 AM, Xie, Huawei wrote: > On 2/23/2016 12:23 AM, Tom Kiely wrote: >> Hi, >> Sorry I missed the last few messages until now. I'm happy with >> just removing the "if". Kyle, when you say you fixed it, do you mean >> that you will push the patch or have already done so ? >> Thanks, >> Tom > Could you please send the patch? >
On Fri, Mar 4, 2016 at 3:11 AM, Tom Kiely <tkiely@brocade.com> wrote: > Sure. > Tom > > > On 03/04/2016 06:16 AM, Xie, Huawei wrote: >> >> On 2/23/2016 12:23 AM, Tom Kiely wrote: >>> >>> Hi, >>> Sorry I missed the last few messages until now. I'm happy with >>> just removing the "if". Kyle, when you say you fixed it, do you mean >>> that you will push the patch or have already done so ? >>> Thanks, >>> Tom >> >> Could you please send the patch? >> > I should have replied to this earlier. I submitted a patch last week: http://dpdk.org/dev/patchwork/patch/10904/
On Fri, Mar 04, 2016 at 08:25:07AM -0500, Kyle Larose wrote: > On Fri, Mar 4, 2016 at 3:11 AM, Tom Kiely <tkiely@brocade.com> wrote: > > Sure. > > Tom > > > > > > On 03/04/2016 06:16 AM, Xie, Huawei wrote: > >> > >> On 2/23/2016 12:23 AM, Tom Kiely wrote: > >>> > >>> Hi, > >>> Sorry I missed the last few messages until now. I'm happy with > >>> just removing the "if". Kyle, when you say you fixed it, do you mean > >>> that you will push the patch or have already done so ? > >>> Thanks, > >>> Tom > >> > >> Could you please send the patch? > >> > > > > I should have replied to this earlier. I submitted a patch last week: > http://dpdk.org/dev/patchwork/patch/10904/ Thanks, Kyle. Unfortunately the patch you submitted is missing your signoff. Can you perhaps resubmit it as a V2 with the necessary sign-off as described in the contributors guide: http://dpdk.org/doc/guides/contributing/patches.html#commit-messages-body Huawei or Tom, could one of you guys perhaps review and ack the patch once it's submitted with a signoff? Thanks, /Bruce
On Wed, Mar 9, 2016 at 4:37 PM, Bruce Richardson <bruce.richardson@intel.com> wrote: > On Fri, Mar 04, 2016 at 08:25:07AM -0500, Kyle Larose wrote: >> On Fri, Mar 4, 2016 at 3:11 AM, Tom Kiely <tkiely@brocade.com> wrote: >> > Sure. >> > Tom >> > >> > >> > On 03/04/2016 06:16 AM, Xie, Huawei wrote: >> >> >> >> On 2/23/2016 12:23 AM, Tom Kiely wrote: >> >>> >> >>> Hi, >> >>> Sorry I missed the last few messages until now. I'm happy with >> >>> just removing the "if". Kyle, when you say you fixed it, do you mean >> >>> that you will push the patch or have already done so ? >> >>> Thanks, >> >>> Tom >> >> >> >> Could you please send the patch? >> >> >> > >> >> I should have replied to this earlier. I submitted a patch last week: >> http://dpdk.org/dev/patchwork/patch/10904/ > > Thanks, Kyle. Unfortunately the patch you submitted is missing your signoff. > Can you perhaps resubmit it as a V2 with the necessary sign-off as described > in the contributors guide: > http://dpdk.org/doc/guides/contributing/patches.html#commit-messages-body > Hey Bruce, Thanks. I signed off, and resubmitted the patch. Hopefully I didn't make any other amateur mistakes this time! > Huawei or Tom, could one of you guys perhaps review and ack the patch once it's > submitted with a signoff? > > Thanks, > /Bruce
diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c index 5770fa2..a95e234 100644 --- a/drivers/net/virtio/virtio_rxtx.c +++ b/drivers/net/virtio/virtio_rxtx.c @@ -586,7 +586,8 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t nb_pkts) if (likely(num > DESC_PER_CACHELINE)) num = num - ((rxvq->vq_used_cons_idx + num) % DESC_PER_CACHELINE); - if (num == 0) + /* Refill free descriptors even if no pkts recvd */ + if (num == 0 && virtqueue_full(rxvq)) return 0; num = virtqueue_dequeue_burst_rx(rxvq, rcv_pkts, len, num); @@ -683,7 +684,8 @@ virtio_recv_mergeable_pkts(void *rx_queue, virtio_rmb(); - if (nb_used == 0) + /* Refill free descriptors even if no pkts recvd */ + if (nb_used == 0 && virtqueue_full(rxvq)) return 0; PMD_RX_LOG(DEBUG, "used:%d\n", nb_used);