From: "Wang, Zhihong" <zhihong.wang@intel.com>
To: Jianbo Liu <jianbo.liu@linaro.org>
Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>,
Maxime Coquelin <maxime.coquelin@redhat.com>,
"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v3 0/5] vhost: optimize enqueue
Date: Mon, 10 Oct 2016 07:25:34 +0000 [thread overview]
Message-ID: <8F6C2BD409508844A0EFC19955BE09414E7BC2C1@SHSMSX103.ccr.corp.intel.com> (raw)
In-Reply-To: <CAP4Qi3-5_5aAATEqnHhNtH0j6Q_VkzF4xbZQGZYbN5KA6oEX_g@mail.gmail.com>
> -----Original Message-----
> From: Jianbo Liu [mailto:jianbo.liu@linaro.org]
> Sent: Monday, October 10, 2016 2:58 PM
> To: Wang, Zhihong <zhihong.wang@intel.com>
> Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>; Maxime Coquelin
> <maxime.coquelin@redhat.com>; dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v3 0/5] vhost: optimize enqueue
>
> On 10 October 2016 at 14:22, Wang, Zhihong <zhihong.wang@intel.com>
> wrote:
> >
> >
> >> -----Original Message-----
> >> From: Jianbo Liu [mailto:jianbo.liu@linaro.org]
> >> Sent: Monday, October 10, 2016 1:32 PM
> >> To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> >> Cc: Wang, Zhihong <zhihong.wang@intel.com>; Maxime Coquelin
> >> <maxime.coquelin@redhat.com>; dev@dpdk.org
> >> Subject: Re: [dpdk-dev] [PATCH v3 0/5] vhost: optimize enqueue
> >>
> >> On 10 October 2016 at 10:44, Yuanhan Liu <yuanhan.liu@linux.intel.com>
> >> wrote:
> >> > On Sun, Oct 09, 2016 at 12:09:07PM +0000, Wang, Zhihong wrote:
> >> >> > > > Tested with testpmd, host: txonly, guest: rxonly
> >> >> > > > size (bytes) improvement (%)
> >> >> > > > 64 4.12
> >> >> > > > 128 6
> >> >> > > > 256 2.65
> >> >> > > > 512 -1.12
> >> >> > > > 1024 -7.02
> >> >> > >
> >> >> > > There is a difference between Zhihong's code and the old I spotted
> in
> >> >> > > the first time: Zhihong removed the avail_idx prefetch. I
> understand
> >> >> > > the prefetch becomes a bit tricky when mrg-rx code path is
> >> considered;
> >> >> > > thus, I didn't comment on that.
> >> >> > >
> >> >> > > That's one of the difference that, IMO, could drop a regression. I
> then
> >> >> > > finally got a chance to add it back.
> >> >> > >
> >> >> > > A rough test shows it improves the performance of 1400B packet
> size
> >> >> > greatly
> >> >> > > in the "txonly in host and rxonly in guest" case: +33% is the number
> I
> >> get
> >> >> > > with my test server (Ivybridge).
> >> >> >
> >> >> > Thanks Yuanhan! I'll validate this on x86.
> >> >>
> >> >> Hi Yuanhan,
> >> >>
> >> >> Seems your code doesn't perform correctly. I write a new version
> >> >> of avail idx prefetch but didn't see any perf benefit.
> >> >>
> >> >> To be honest I doubt the benefit of this idea. The previous mrg_off
> >> >> code has this method but doesn't give any benefits.
> >> >
> >> > Good point. I thought of that before, too. But you know that I made it
> >> > in rush, that I didn't think further and test more.
> >> >
> >> > I looked the code a bit closer this time, and spotted a bug: the prefetch
> >> > actually didn't happen, due to following code piece:
> >> >
> >> > if (vq->next_avail_idx >= NR_AVAIL_IDX_PREFETCH) {
> >> > prefetch_avail_idx(vq);
> >> > ...
> >> > }
> >> >
> >> > Since vq->next_avail_idx is set to 0 at the entrance of enqueue path,
> >> > prefetch_avail_idx() will be called. The fix is easy though: just put
> >> > prefetch_avail_idx before invoking enqueue_packet.
> >> >
> >> > In summary, Zhihong is right, I see no more gains with that fix :(
> >> >
> >> > However, as stated, that's kind of the only difference I found between
> >> > yours and the old code, that maybe it's still worthwhile to have a
> >> > test on ARM, Jianbo?
> >> >
> >> I haven't tested it, but I think it could be no improvement for ARM either.
> >>
> >> A smalll suggestion for enqueue_packet:
> >>
> >> .....
> >> + /* start copy from mbuf to desc */
> >> + while (mbuf_avail || mbuf->next) {
> >> .....
> >>
> >> Considering pkt_len is in the first cache line (same as data_len),
> >> while next pointer is in the second cache line,
> >> is it better to check the total packet len, instead of the last mbuf's
> >> next pointer to jump out of while loop and avoid possible cache miss?
> >
> > Jianbo,
> >
> > Thanks for the reply!
> >
> > This idea sounds good, but it won't help the general perf in my
> > opinion, since the 2nd cache line is accessed anyway prior in
> > virtio_enqueue_offload.
> >
> Yes, you are right. I'm thinking of prefetching beforehand.
> And if it's a chained mbuf, virtio_enqueue_offload will not be called
> in next loop.
>
> > Also this would bring a NULL check when actually access mbuf->next.
> >
> > BTW, could you please publish the number of:
> >
> > 1. mrg_rxbuf=on, comparison between original and original + this patch
> >
> > 2. mrg_rxbuf=off, comparison between original and original + this patch
> >
> > So we can have a whole picture of how this patch impact on ARM platform.
> >
> I think you already have got many results in my previous emails.
> Sorry I can't test right now and busy with other things.
We're still missing mrg on data.
next prev parent reply other threads:[~2016-10-10 7:25 UTC|newest]
Thread overview: 140+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-16 3:50 [dpdk-dev] [PATCH] optimize vhost enqueue Zhihong Wang
2016-08-16 13:59 ` Maxime Coquelin
2016-08-17 1:45 ` Wang, Zhihong
2016-08-17 2:38 ` Yuanhan Liu
2016-08-17 6:41 ` Wang, Zhihong
2016-08-17 9:17 ` Maxime Coquelin
2016-08-17 9:51 ` Yuanhan Liu
2016-08-18 13:44 ` Wang, Zhihong
2016-08-17 10:07 ` Wang, Zhihong
2016-08-18 6:33 ` [dpdk-dev] [PATCH v2 0/6] vhost: optimize enqueue Zhihong Wang
2016-08-18 6:33 ` [dpdk-dev] [PATCH v2 1/6] vhost: rewrite enqueue Zhihong Wang
2016-08-19 2:39 ` Yuanhan Liu
2016-08-19 7:07 ` Wang, Zhihong
2016-08-18 6:33 ` [dpdk-dev] [PATCH v2 2/6] vhost: remove obsolete Zhihong Wang
2016-08-19 2:32 ` Yuanhan Liu
2016-08-19 7:08 ` Wang, Zhihong
2016-08-18 6:33 ` [dpdk-dev] [PATCH v2 3/6] vhost: remove useless volatile Zhihong Wang
2016-08-18 6:33 ` [dpdk-dev] [PATCH v2 4/6] vhost: add desc prefetch Zhihong Wang
2016-08-18 6:33 ` [dpdk-dev] [PATCH v2 5/6] vhost: batch update used ring Zhihong Wang
2016-08-18 6:33 ` [dpdk-dev] [PATCH v2 6/6] vhost: optimize cache access Zhihong Wang
2016-08-19 5:43 ` [dpdk-dev] [PATCH v3 0/5] vhost: optimize enqueue Zhihong Wang
2016-08-19 5:43 ` [dpdk-dev] [PATCH v3 1/5] vhost: rewrite enqueue Zhihong Wang
2016-08-22 9:35 ` Maxime Coquelin
2016-08-23 2:27 ` Wang, Zhihong
2016-08-25 4:00 ` Yuanhan Liu
2016-08-19 5:43 ` [dpdk-dev] [PATCH v3 2/5] vhost: remove useless volatile Zhihong Wang
2016-08-19 5:43 ` [dpdk-dev] [PATCH v3 3/5] vhost: add desc prefetch Zhihong Wang
2016-08-19 5:43 ` [dpdk-dev] [PATCH v3 4/5] vhost: batch update used ring Zhihong Wang
2016-08-25 3:48 ` Yuanhan Liu
2016-08-25 5:19 ` Wang, Zhihong
2016-08-19 5:43 ` [dpdk-dev] [PATCH v3 5/5] vhost: optimize cache access Zhihong Wang
2016-08-22 8:11 ` [dpdk-dev] [PATCH v3 0/5] vhost: optimize enqueue Maxime Coquelin
2016-08-22 10:01 ` Maxime Coquelin
2016-08-22 10:35 ` Thomas Monjalon
2016-08-24 3:37 ` Wang, Zhihong
2016-08-23 2:31 ` Wang, Zhihong
2016-08-23 10:43 ` Wang, Zhihong
2016-08-23 12:16 ` Maxime Coquelin
2016-08-23 12:22 ` Yuanhan Liu
2016-08-23 2:15 ` Wang, Zhihong
2016-09-21 8:50 ` Jianbo Liu
2016-09-21 9:27 ` Wang, Zhihong
2016-09-21 12:54 ` Jianbo Liu
2016-09-22 2:11 ` Wang, Zhihong
2016-09-22 2:29 ` Yuanhan Liu
2016-09-22 5:47 ` Jianbo Liu
2016-09-22 6:58 ` Wang, Zhihong
2016-09-22 9:01 ` Jianbo Liu
2016-09-22 10:04 ` Wang, Zhihong
2016-09-22 14:41 ` Jianbo Liu
2016-09-23 2:56 ` Wang, Zhihong
2016-09-23 10:41 ` Jianbo Liu
2016-09-23 13:41 ` Thomas Monjalon
2016-09-25 5:41 ` Wang, Zhihong
2016-09-26 5:12 ` Jianbo Liu
2016-09-26 5:25 ` Wang, Zhihong
2016-09-26 5:38 ` Jianbo Liu
2016-09-26 6:00 ` Wang, Zhihong
2016-09-26 4:24 ` Jianbo Liu
2016-09-26 5:37 ` Luke Gorrie
2016-09-26 5:40 ` Jianbo Liu
2016-09-27 10:21 ` Yuanhan Liu
2016-09-27 16:45 ` Wang, Zhihong
2016-10-09 12:09 ` Wang, Zhihong
2016-10-10 2:44 ` Yuanhan Liu
2016-10-10 5:31 ` Jianbo Liu
2016-10-10 6:22 ` Wang, Zhihong
2016-10-10 6:57 ` Jianbo Liu
2016-10-10 7:25 ` Wang, Zhihong [this message]
2016-10-12 2:53 ` Yuanhan Liu
2016-10-12 12:22 ` Wang, Zhihong
2016-10-12 15:31 ` Thomas Monjalon
2016-10-13 1:21 ` Wang, Zhihong
2016-10-13 3:51 ` Jianbo Liu
2016-10-13 5:33 ` Yuanhan Liu
2016-10-13 5:35 ` Yuanhan Liu
2016-10-13 6:02 ` Wang, Zhihong
2016-10-13 7:54 ` Maxime Coquelin
2016-10-13 9:23 ` Maxime Coquelin
2016-10-14 10:11 ` Yuanhan Liu
2016-08-30 3:35 ` [dpdk-dev] [PATCH v4 0/6] " Zhihong Wang
2016-08-30 3:35 ` [dpdk-dev] [PATCH v4 1/6] vhost: fix windows vm hang Zhihong Wang
2016-09-05 5:24 ` [dpdk-dev] [dpdk-stable] " Yuanhan Liu
2016-09-05 5:25 ` Wang, Zhihong
2016-09-05 5:40 ` Yuanhan Liu
2016-08-30 3:36 ` [dpdk-dev] [PATCH v4 2/6] vhost: rewrite enqueue Zhihong Wang
2016-09-05 6:39 ` Yuanhan Liu
2016-09-07 5:33 ` Yuanhan Liu
2016-09-07 5:39 ` Wang, Zhihong
2016-08-30 3:36 ` [dpdk-dev] [PATCH v4 3/6] vhost: remove useless volatile Zhihong Wang
2016-08-30 3:36 ` [dpdk-dev] [PATCH v4 4/6] vhost: add desc prefetch Zhihong Wang
2016-08-30 3:36 ` [dpdk-dev] [PATCH v4 5/6] vhost: batch update used ring Zhihong Wang
2016-08-30 3:36 ` [dpdk-dev] [PATCH v4 6/6] vhost: optimize cache access Zhihong Wang
2016-09-09 3:39 ` [dpdk-dev] [PATCH v5 0/6] vhost: optimize enqueue Zhihong Wang
2016-09-09 3:39 ` [dpdk-dev] [PATCH v5 1/6] vhost: fix windows vm hang Zhihong Wang
2016-09-09 3:39 ` [dpdk-dev] [PATCH v5 2/6] vhost: rewrite enqueue Zhihong Wang
2016-09-12 15:42 ` Maxime Coquelin
2016-09-14 8:20 ` Wang, Zhihong
2016-09-15 16:35 ` Maxime Coquelin
2016-09-12 16:26 ` Maxime Coquelin
2016-09-14 8:22 ` Wang, Zhihong
2016-09-18 14:19 ` Yuanhan Liu
2016-09-19 3:29 ` Wang, Zhihong
2016-09-09 3:39 ` [dpdk-dev] [PATCH v5 3/6] vhost: remove useless volatile Zhihong Wang
2016-09-09 3:39 ` [dpdk-dev] [PATCH v5 4/6] vhost: add desc prefetch Zhihong Wang
2016-09-09 3:39 ` [dpdk-dev] [PATCH v5 5/6] vhost: batch update used ring Zhihong Wang
2016-09-12 15:45 ` Maxime Coquelin
2016-09-14 8:43 ` Wang, Zhihong
2016-09-15 16:38 ` Maxime Coquelin
2016-09-18 2:55 ` Yuanhan Liu
2016-09-18 2:57 ` Wang, Zhihong
2016-09-09 3:39 ` [dpdk-dev] [PATCH v5 6/6] vhost: optimize cache access Zhihong Wang
2016-09-12 13:52 ` [dpdk-dev] [PATCH v5 0/6] vhost: optimize enqueue Maxime Coquelin
2016-09-12 13:56 ` Maxime Coquelin
2016-09-12 14:01 ` Yuanhan Liu
2016-09-20 2:00 ` [dpdk-dev] [PATCH v6 " Zhihong Wang
2016-09-20 2:00 ` [dpdk-dev] [PATCH v6 1/6] vhost: fix windows vm hang Zhihong Wang
2016-10-13 6:18 ` [dpdk-dev] [dpdk-stable] " Yuanhan Liu
2016-09-20 2:00 ` [dpdk-dev] [PATCH v6 2/6] vhost: rewrite enqueue Zhihong Wang
2016-09-22 9:58 ` Jianbo Liu
2016-09-22 10:13 ` Wang, Zhihong
2016-09-20 2:00 ` [dpdk-dev] [PATCH v6 3/6] vhost: remove useless volatile Zhihong Wang
2016-09-20 2:00 ` [dpdk-dev] [PATCH v6 4/6] vhost: add desc prefetch Zhihong Wang
2016-09-20 2:00 ` [dpdk-dev] [PATCH v6 5/6] vhost: batch update used ring Zhihong Wang
2016-09-20 2:00 ` [dpdk-dev] [PATCH v6 6/6] vhost: optimize cache access Zhihong Wang
2016-09-21 2:26 ` [dpdk-dev] [PATCH v6 0/6] vhost: optimize enqueue Yuanhan Liu
2016-09-21 4:39 ` Maxime Coquelin
2016-10-14 9:34 ` [dpdk-dev] [PATCH v7 0/7] vhost: optimize mergeable Rx path Yuanhan Liu
2016-10-14 9:34 ` [dpdk-dev] [PATCH v7 1/7] vhost: remove useless volatile Yuanhan Liu
2016-10-14 9:34 ` [dpdk-dev] [PATCH v7 2/7] vhost: optimize cache access Yuanhan Liu
2016-10-14 9:34 ` [dpdk-dev] [PATCH v7 3/7] vhost: simplify mergeable Rx vring reservation Yuanhan Liu
2016-10-25 22:08 ` Thomas Monjalon
2016-10-26 2:56 ` Yuanhan Liu
2016-10-14 9:34 ` [dpdk-dev] [PATCH v7 4/7] vhost: use last avail idx for avail ring reservation Yuanhan Liu
2016-10-14 9:34 ` [dpdk-dev] [PATCH v7 5/7] vhost: shadow used ring update Yuanhan Liu
2016-10-14 9:34 ` [dpdk-dev] [PATCH v7 6/7] vhost: prefetch avail ring Yuanhan Liu
2016-10-14 9:34 ` [dpdk-dev] [PATCH v7 7/7] vhost: retrieve avail head once Yuanhan Liu
2016-10-18 2:25 ` [dpdk-dev] [PATCH v7 0/7] vhost: optimize mergeable Rx path Jianbo Liu
2016-10-18 14:53 ` Maxime Coquelin
2016-10-21 7:51 ` Yuanhan Liu
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