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

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

> -----Original Message-----
> From: Ding, Xuan <xuan.ding@intel.com>
> Sent: Friday, July 8, 2022 3:04 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
> 
> 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.

The fix is for a critical issue, I tested dpdk22.07-rc3 with the patch, 
the performance drop introduced by refactoring have been fixed 
and no other regressions were seen as a result of the patch, 
but the packed ring still exist drop around 5%.  

Tested-by: Xingguang He<xingguang.he@intel.com>

> 
> 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.

I tested the performance of Vhost before and after checksum offload patch series, 
there exist  ~5% performance drop.

> 
> Could you help to double check this patch series, is it as expected?
> Your assistance is really appreciated.
> 
> Regards,
> Xuan
> 
> >
> > > Thanks,
> > > Chenbo
> > >
> >
> > Thanks,
> > Maxime