> -----Original Message----- > From: Will Deacon [mailto:will@xxxxxxxxxx] > Sent: 22 April 2021 18:09 > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx> > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; kvmarm@xxxxxxxxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx; maz@xxxxxxxxxx; catalin.marinas@xxxxxxx; > james.morse@xxxxxxx; julien.thierry.kdev@xxxxxxxxx; > suzuki.poulose@xxxxxxx; jean-philippe@xxxxxxxxxx; julien@xxxxxxx; Linuxarm > <linuxarm@xxxxxxxxxx> > Subject: Re: [PATCH v4 00/16] kvm/arm: Align the VMID allocation with the > arm64 ASID one > > On Wed, Apr 14, 2021 at 12:22:56PM +0100, Shameer Kolothum wrote: > > Hi, > > > > This is an attempt to revive this series originally posted by > > Julien Grall[1]. The main motive to work on this now is because > > of the requirement to have Pinned KVM VMIDs and the RFC discussion > > for the same basically suggested[2] to have a common/better vmid > > allocator for KVM which this series provides. > > > > Major Changes from v3: > > > > -Changes related to Pinned ASID support. > > -Changes to take care KPTI related bits reservation. > > -Dropped support for 32 bit KVM. > > -Rebase to 5.12-rc7 > > > > Individual patches have change history for any major changes > > from v3. > > > > Tests were performed on a HiSilicon D06 platform and so far not observed > > any regressions. > > > > For ASID allocation, > > > > Avg of 10 runs(hackbench -s 512 -l 200 -g 300 -f 25 -P), > > 5.12-rc7: Time:18.8119 > > 5.12-rc7+v4: Time: 18.459 > > > > ~1.8% improvement. > > > > For KVM VMID, > > > > The measurement was made with maxcpus set to 8 and with the > > number of VMID limited to 4-bit. The test involves running > > concurrently 40 guests with 2 vCPUs. Each guest will then > > execute hackbench 5 times before exiting. > > > > The performance difference between the current algo and the > > new one are(ag. of 10 runs): > > - 1.9% less exit from the guest > > - 0.7% faster > > > > For complete series, please see, > > https://github.com/hisilicon/kernel-dev/tree/private-v5.12-rc7-asid-v4 > > > > Please take a look and let me know your feedback. > > Although I think aligning the two algorithms makes sense, I'm not completely > sold on the need to abstract all this into a library and whether the > additional indirection is justified. > > It would be great to compare this approach with one where portions of the > code are duplicated into a separate VMID allocator. Have you tried that to > see what it looks like? Doesn't need to be a proper patch set, but comparing > the end result might help to evaluate the proposal here. Ok. I will give it a go and get back. Thanks, Shameer _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
