[PATCH 1/5] iommu/arm-smmu-v3: put off the execution of TLBI* to reduce lock confliction

[Jonathan Cameron]

On Thu, 20 Jul 2017 15:07:05 -0400
Nate Watterson <nwatters at codeaurora.org> wrote:

> Hi Jonathan,
> 
> [...]
> >>>>>        
> >>> Hi All,
> >>>
> >>> I'm a bit of late entry to this discussion.  Just been running some more
> >>> detailed tests on our d05 boards and wanted to bring some more numbers to
> >>> the discussion.
> >>>
> >>> All tests against 4.12 with the following additions:
> >>> * Robin's series removing the io-pgtable spinlock (and a few recent fixes)
> >>> * Cherry picked updates to the sas driver, merged prior to 4.13-rc1
> >>> * An additional HNS (network card) bug fix that will be upstreamed shortly.
> >>>
> >>> I've broken the results down into this patch and this patch + the remainder
> >>> of the set. As leizhen mentioned we got a nice little performance
> >>> bump from Robin's series so that was applied first (as it's in mainline now)
> >>>
> >>> SAS tests were fio with noop scheduler, 4k block size and various io depths
> >>> 1 process per disk.  Note this is probably a different setup to leizhen's
> >>> original numbers.
> >>>
> >>> Precentages are off the performance seen with the smmu disabled.
> >>> SAS
> >>> 4.12 - none of this series.
> >>> SMMU disabled
> >>> read io-depth 32 -   384K IOPS (100%)
> >>> read io-depth 2048 - 950K IOPS (100%)
> >>> rw io-depth 32 -     166K IOPS (100%)
> >>> rw io-depth 2048 -   340K IOPS (100%)
> >>>
> >>> SMMU enabled
> >>> read io-depth 32 -   201K IOPS (52%)
> >>> read io-depth 2048 - 306K IOPS (32%)
> >>> rw io-depth 32 -     99K  IOPS (60%)
> >>> rw io-depth 2048 -   150K IOPS (44%)
> >>>
> >>> Robin's recent series with fixes as seen on list (now merged)
> >>> SMMU enabled.
> >>> read io-depth 32 -   208K IOPS (54%)
> >>> read io-depth 2048 - 335K IOPS (35%)
> >>> rw io-depth 32 -     105K IOPS (63%)
> >>> rw io-depth 2048 -   165K IOPS (49%)
> >>>
> >>> 4.12 + Robin's series + just this patch SMMU enabled
> >>>
> >>> (iommu/arm-smmu-v3: put of the execution of TLBI* to reduce lock conflict)
> >>>
> >>> read io-depth 32 -   225K IOPS (59%)
> >>> read io-depth 2048 - 365K IOPS (38%)
> >>> rw io-depth 32 -     110K IOPS (66%)
> >>> rw io-depth 2048 -   179K IOPS (53%)
> >>>
> >>> 4.12 + Robin's series + Second part of this series
> >>>
> >>> (iommu/arm-smmu-v3: put of the execution of TLBI* to reduce lock conflict)
> >>> (iommu: add a new member unmap_tlb_sync into struct iommu_ops)
> >>> (iommu/arm-smmu-v3: add supprot for unmap an iova range with only on tlb sync)
> >>> (iommu/arm-smmu: add support for unmap of a memory range with only one tlb sync)
> >>>
> >>> read io-depth 32 -    225K IOPS (59%)
> >>> read io-depth 2048 -  833K IOPS (88%)
> >>> rw io-depth 32 -      112K IOPS (67%)
> >>> rw io-depth 2048 -    220K IOPS (65%)
> >>>
> >>> Robin's series gave us small gains across the board (3-5% recovered)
> >>> relative to the no smmu performance (which we are taking as the ideal case)
> >>>
> >>> This first patch gets us back another 2-5% of the no smmu performance
> >>>
> >>> The next few patches get us very little advantage on the small io-depths
> >>> but make a large difference to the larger io-depths - in particular the
> >>> read IOPS which is over twice as fast as without the series.
> >>>
> >>> For HNS it seems that we are less dependent on the SMMU performance and
> >>> can reach the non SMMU speed.
> >>>
> >>> Tests with
> >>> iperf -t 30 -i 10 -c IPADDRESS -P 3 last 10 seconds taken to avoid any
> >>> initial variability.
> >>>
> >>> The server end of the link was always running with smmu v3 disabled
> >>> so as to act as a fast sink of the data. Some variation seen across
> >>> repeat runs.
> >>>
> >>> Mainline v4.12 + network card fix
> >>> NO SMMU
> >>> 9.42 GBits/sec
> >>>
> >>> SMMU
> >>> 4.36 GBits/sec (46%)
> >>>
> >>> Robin's io-pgtable spinlock series
> >>>
> >>> 6.68 to 7.34 (71% - 78% variation across runs)
> >>>
> >>> Just this patch SMMU enabled
> >>>
> >>> (iommu/arm-smmu-v3: put of the execution of TLBI* to reduce lock conflict)
> >>>
> >>> 7.96-8.8 GBits/sec (85% - 94%  some variation across runs)
> >>>
> >>> Full series
> >>>
> >>> (iommu/arm-smmu-v3: put of the execution of TLBI* to reduce lock conflict)
> >>> (iommu: add a new member unmap_tlb_sync into struct iommu_ops)
> >>> (iommu/arm-smmu-v3: add supprot for unmap an iova range with only on tlb sync)
> >>> (iommu/arm-smmu: add support for unmap of a memory range with only one tlb sync)
> >>>
> >>> 9.42 GBits/Sec (100%)
> >>>
> >>> So HNS test shows a greater boost from Robin's series and this first patch.
> >>> This is most likely because the HNS test is not putting as high a load on
> >>> the SMMU and associated code as the SAS test.
> >>>
> >>> In both cases however, this shows that both parts of this patch
> >>> series are beneficial.
> >>>
> >>> So on to the questions ;)
> >>>
> >>> Will, you mentioned that along with Robin and Nate you were working on
> >>> a somewhat related strategy to improve the performance.  Any ETA on that?  
> >>
> >> The strategy I was working on is basically equivalent to the second
> >> part of the series. I will test your patches out sometime this week, and
> >> I'll also try to have our performance team run it through their whole
> >> suite.  
> > 
> > Thanks, that's excellent.  Look forward to hearing how it goes.  
> 
> I tested the patches with 4 NVME drives connected to a single SMMU and
> the results seem to be inline with those you've reported.
> 
> FIO - 512k blocksize / io-depth 32 / 1 thread per drive
>   Baseline 4.13-rc1 w/SMMU enabled: 25% of SMMU bypass performance
>   Baseline + Patch 1              : 28%
>   Baseline + Patches 2-5          : 86%
>   Baseline + Complete series      : 100% [!!]
> 
> I saw performance improvements across all of the other FIO profiles I
> tested, although not always as substantial as was seen in the 512k/32/1
> case. The performance of some of the profiles, especially those with
> many threads per drive, remains woeful (often below 20%), but hopefully
> Robin's iova series will help improve that.
Excellent.  Thanks for the info and running the tests.

Even with both series we are still seeing some reduction in over the no-smmu
performance, but to a much lesser extent. 

Jonathan
> 
> > 
> > Particularly useful would be to know if there are particular performance tests
> > that show up anything interesting that we might want to replicate.
> > 
> > Jonathan and Leizhen  
> >>  
> >>>
> >>> As you might imagine, with the above numbers we are very keen to try and
> >>> move forward with this as quickly as possible.
> >>>
> >>> If you want additional testing we would be happy to help.
> >>>
> >>> Thanks,
> >>>
> >>> Jonathan  
> [...]
> 
> -Nate
>