From: Will Deacon <will@kernel.org>
To: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Cc: jean-philippe@linaro.org, julien@xen.org, maz@kernel.org,
linux-kernel@vger.kernel.org, linuxarm@huawei.com,
catalin.marinas@arm.com, kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4 00/16] kvm/arm: Align the VMID allocation with the arm64 ASID one
Date: Thu, 22 Apr 2021 17:08:48 +0100 [thread overview]
Message-ID: <20210422160846.GB2214@willie-the-truck> (raw)
In-Reply-To: <20210414112312.13704-1-shameerali.kolothum.thodi@huawei.com>
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.
Will
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next prev parent reply other threads:[~2021-04-22 16:08 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-14 11:22 [PATCH v4 00/16] kvm/arm: Align the VMID allocation with the arm64 ASID one Shameer Kolothum
2021-04-14 11:22 ` [PATCH v4 01/16] arm64/mm: Introduce asid_info structure and move asid_generation/asid_map to it Shameer Kolothum
2021-04-14 11:22 ` [PATCH v4 02/16] arm64/mm: Move active_asids and reserved_asids to asid_info Shameer Kolothum
2021-04-14 11:22 ` [PATCH v4 03/16] arm64/mm: Move bits " Shameer Kolothum
2021-04-14 11:23 ` [PATCH v4 04/16] arm64/mm: Move the variable lock and tlb_flush_pending " Shameer Kolothum
2021-04-14 11:23 ` [PATCH v4 05/16] arm64/mm: Remove dependency on MM in new_context Shameer Kolothum
2021-04-14 11:23 ` [PATCH v4 06/16] arm64/mm: Introduce NUM_CTXT_ASIDS Shameer Kolothum
2021-04-14 11:23 ` [PATCH v4 07/16] arm64/mm: Move Pinned ASID related variables to asid_info Shameer Kolothum
2021-04-14 11:23 ` [PATCH v4 08/16] arm64/mm: Split asid_inits in 2 parts Shameer Kolothum
2021-04-14 11:23 ` [PATCH v4 09/16] arm64/mm: Split the function check_and_switch_context in 3 parts Shameer Kolothum
2021-04-14 11:23 ` [PATCH v4 10/16] arm64/mm: Split the arm64_mm_context_get/put Shameer Kolothum
2021-04-14 11:23 ` [PATCH v4 11/16] arm64/mm: Introduce a callback to flush the local context Shameer Kolothum
2021-04-14 11:23 ` [PATCH v4 12/16] arm64/mm: Introduce a callback to set reserved bits Shameer Kolothum
2021-04-14 11:23 ` [PATCH v4 13/16] arm64: Move the ASID allocator code in a separate file Shameer Kolothum
2021-04-14 11:23 ` [PATCH v4 14/16] arm64/lib: Add an helper to free memory allocated by the ASID allocator Shameer Kolothum
2021-04-14 11:23 ` [PATCH v4 15/16] arch/arm64: Introduce a capability to tell whether 16-bit VMID is available Shameer Kolothum
2021-04-14 11:23 ` [PATCH v4 16/16] kvm/arm: Align the VMID allocation with the arm64 ASID one Shameer Kolothum
2021-04-22 16:08 ` Will Deacon [this message]
2021-04-23 8:31 ` [PATCH v4 00/16] " Shameerali Kolothum Thodi
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