RE: [PATCH] vhost: fix unnecessary dirty page logging

["He, Xingguang" <xingguang.he@intel.com>]

Hi,

> -----Original Message-----
> From: Ding, Xuan <xuan.ding@intel.com>
> Sent: Friday, July 8, 2022 4:09 PM
> To: Maxime Coquelin <maxime.coquelin@redhat.com>; Xia, Chenbo
> <chenbo.xia@intel.com>
> Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; He, Xingguang
> <xingguang.he@intel.com>; Yang, YvonneX <yvonnex.yang@intel.com>;
> Jiang, Cheng1 <cheng1.jiang@intel.com>
> Subject: RE: [PATCH] vhost: fix unnecessary dirty page logging
> 
> 
> 
> > -----Original Message-----
> > From: Maxime Coquelin <maxime.coquelin@redhat.com>
> > Sent: 2022年7月8日 15:58
> > To: Ding, Xuan <xuan.ding@intel.com>; Xia, Chenbo
> > <chenbo.xia@intel.com>
> > Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; He, Xingguang
> > <xingguang.he@intel.com>; Yang, YvonneX <yvonnex.yang@intel.com>;
> > Jiang,
> > Cheng1 <cheng1.jiang@intel.com>
> > Subject: Re: [PATCH] vhost: fix unnecessary dirty page logging
> >
> > Hi,
> >
> > On 7/8/22 09:04, Ding, Xuan wrote:
> > > Hi,
> > >
> > >> -----Original Message-----
> > >> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> > >> Sent: 2022年7月7日 19:31
> > >> To: Xia, Chenbo <chenbo.xia@intel.com>; Ding, Xuan
> > >> <xuan.ding@intel.com>
> > >> Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; He, Xingguang
> > >> <xingguang.he@intel.com>; Yang, YvonneX <yvonnex.yang@intel.com>;
> > >> Jiang,
> > >> Cheng1 <cheng1.jiang@intel.com>
> > >> Subject: Re: [PATCH] vhost: fix unnecessary dirty page logging
> > >>
> > >>
> > >>
> > >> On 7/7/22 11:51, Xia, Chenbo wrote:
> > >>>> -----Original Message-----
> > >>>> From: Ding, Xuan <xuan.ding@intel.com>
> > >>>> Sent: Thursday, July 7, 2022 2:55 PM
> > >>>> To: maxime.coquelin@redhat.com; Xia, Chenbo
> > >>>> <chenbo.xia@intel.com>
> > >>>> Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; He, Xingguang
> > >>>> <xingguang.he@intel.com>; Yang, YvonneX
> <yvonnex.yang@intel.com>;
> > >>>> Jiang,
> > >>>> Cheng1 <cheng1.jiang@intel.com>; Ding, Xuan <xuan.ding@intel.com>
> > >>>> Subject: [PATCH] vhost: fix unnecessary dirty page logging
> > >>>>
> > >>>> From: Xuan Ding <xuan.ding@intel.com>
> > >>>>
> > >>>> The dirty page logging is only required in vhost enqueue
> > >>>> direction for live migration. This patch removes the unnecessary
> > >>>> dirty page logging in vhost dequeue direction. Otherwise, it will
> > >>>> result in a performance drop. Some if-else judgements are also
> > >>>> optimized to improve
> > >> performance.
> > >>>>
> > >>>> Fixes: 6d823bb302c7 ("vhost: prepare sync for descriptor to mbuf
> > >>>> refactoring")
> > >>>> Fixes: b6eee3e83402 ("vhost: fix sync dequeue offload")
> > >>>>
> > >>>> Signed-off-by: Xuan Ding <xuan.ding@intel.com>
> > >>>> ---
> > >>>
> > >>> Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
> > >>>
> > >>> Although it's late in release, we can consider to merge this as I
> > >>> see it impacts the performance by 5%:
> > >>>
> > >>
> >
> http://inbox.dpdk.org/dev/BYAPR11MB2711F13CDA2B0A4535A6591EFE839
> @B
> > >> YAPR
> > >>> 11MB2711.namprd11.prod.outlook.com/T/#t
> > >>
> > >> Yes, I raised we need it in -rc4 at today's Release status meeting.
> > >> I'll review it today.
> > >>
> > >>> But also, it will be good to know the performance issue is solved
> > >>> by sharing the test results.
> > >>
> > >> Yes, Intel performance results would be appreciated.
> > >
> > > This fix patch is for the issue reported at 22.07-rc3. The
> > > refactoring patch
> > brings a 3%~5% perf drop in vhost sync path.
> > > With fix patch, the perf drop introduced by refactoring is solved.
> >
> > Good.
> >
> > > However, the testing result shows there still exists ~5% packed ring
> > > perf drop
> > compared with 22.03.
> > > We find the improving checksum offload patch series in 22.07 may
> > > contribute
> > to the packed ring perf drop.
> > > Because we always do checksum checks in PMD.
> > >
> > > Could you help to double check this patch series, is it as expected?
> > > Your assistance is really appreciated.
> >
> > I will look again, but if your analysis is right, there's not much we
> > can do. The series is filling gaps in the checksum offload support.

What is the result of your investigation? As dpdk-22.07 will be released soon, 
I'd like to know your advice about this issue. Thanks.

> 
> Yes, I think so.
> 
> >
> > I will not have time to work on it for v22.07, we're too late in the
> > cycle. What surprises me is that only packed ring is impacted.
> 
> From the testing results, the packed ring is more sensitive to the patch series,
> while split ring shows a much lower drop in performance.
> 
> Thanks for your support!
> 

Regards,
Xingguang

> Regards,
> Xuan
> 
> >
> > Regards,
> > Maxime
> >
> > >
> > > Regards,
> > > Xuan
> > >
> > >>
> > >>> Thanks,
> > >>> Chenbo
> > >>>
> > >>
> > >> Thanks,
> > >> Maxime
> > >