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

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

> -----Original Message-----
> From: He, Xingguang <xingguang.he@intel.com>
> Sent: Friday, July 8, 2022 3:53 PM
> To: Ding, Xuan <xuan.ding@intel.com>; Maxime Coquelin
> <maxime.coquelin@redhat.com>; Xia, Chenbo <chenbo.xia@intel.com>
> Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@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: 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.

Sorry, the drop of checksum offload patch series is ~3%. 
The drop between DPDK22.03 and DPDK22.07-rc3 is ~5%.  

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