From: David Matlack <dmatlack@google.com>
To: Vipin Sharma <vipinsh@google.com>
Cc: seanjc@google.com, pbonzini@redhat.com, bgardon@google.com,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [Patch v3 2/7] KVM: x86/mmu: Atomically clear SPTE dirty state in the clear-dirty-log flow
Date: Wed, 15 Feb 2023 13:12:12 -0800 [thread overview]
Message-ID: <Y+1KrHYEi1D4T14P@google.com> (raw)
In-Reply-To: <20230211014626.3659152-3-vipinsh@google.com>
On Fri, Feb 10, 2023 at 05:46:21PM -0800, Vipin Sharma wrote:
> Do atomic-AND to clear the dirty state of SPTEs. Optimize clear-dirty-log
> flow by avoiding to go through __handle_changed_spte() and directly call
> kvm_set_pfn_dirty() instead.
>
> Atomic-AND allows to fetch the latest value in SPTE, clear only its
> dirty state and set the new SPTE value. This optimization avoids
> executing unnecessary checks by not calling __handle_changed_spte().
>
> With the removal of tdp_mmu_set_spte_no_dirty_log(), "record_dirty_log"
> parameter in __tdp_mmu_set_spte() is now obsolete. It will always be set
> to true by its caller. This dead code will be cleaned up in future
> commits.
>
> Tested on a VM (160 vCPUs, 160 GB memory) and found that performance of clear
> dirty log stage improved by ~40% in dirty_log_perf_test
>
> Before optimization:
> --------------------
> Iteration 1 clear dirty log time: 3.638543593s
> Iteration 2 clear dirty log time: 3.145032742s
> Iteration 3 clear dirty log time: 3.142340358s
> Clear dirty log over 3 iterations took 9.925916693s. (Avg 3.308638897s/iteration)
>
> After optimization:
> -------------------
> Iteration 1 clear dirty log time: 2.318988110s
> Iteration 2 clear dirty log time: 1.794470164s
> Iteration 3 clear dirty log time: 1.791668628s
> Clear dirty log over 3 iterations took 5.905126902s. (Avg 1.968375634s/iteration)
>
> Signed-off-by: Vipin Sharma <vipinsh@google.com>
Reviewed-by: David Matlack <dmatlack@google.com>
next prev parent reply other threads:[~2023-02-15 21:12 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-11 1:46 [Patch v3 0/7] Optimize clear dirty log Vipin Sharma
2023-02-11 1:46 ` [Patch v3 1/7] KVM: x86/mmu: Add a helper function to check if an SPTE needs atomic write Vipin Sharma
2023-02-11 1:46 ` [Patch v3 2/7] KVM: x86/mmu: Atomically clear SPTE dirty state in the clear-dirty-log flow Vipin Sharma
2023-02-15 21:12 ` David Matlack [this message]
2023-03-17 22:59 ` Sean Christopherson
2023-03-17 23:50 ` Vipin Sharma
2023-02-11 1:46 ` [Patch v3 3/7] KVM: x86/mmu: Remove "record_dirty_log" in __tdp_mmu_set_spte() Vipin Sharma
2023-02-15 21:10 ` David Matlack
2023-02-11 1:46 ` [Patch v3 4/7] KVM: x86/mmu: Optimize SPTE change for aging gfn range Vipin Sharma
2023-02-15 21:15 ` David Matlack
2023-03-21 0:51 ` Sean Christopherson
2023-02-11 1:46 ` [Patch v3 5/7] KVM: x86/mmu: Remove "record_acc_track" in __tdp_mmu_set_spte() Vipin Sharma
2023-02-22 19:31 ` David Matlack
2023-02-11 1:46 ` [Patch v3 6/7] KVM: x86/mmu: Remove handle_changed_spte_dirty_log() Vipin Sharma
2023-02-22 19:36 ` David Matlack
2023-02-11 1:46 ` [Patch v3 7/7] KVM: x86/mmu: Merge all handle_changed_pte* functions Vipin Sharma
2023-02-22 19:42 ` David Matlack
2023-03-17 22:51 ` Sean Christopherson
2023-03-17 23:48 ` Vipin Sharma
2023-03-17 22:57 ` [Patch v3 0/7] Optimize clear dirty log Sean Christopherson
2023-03-17 23:51 ` Vipin Sharma
2023-03-21 0:41 ` Sean Christopherson
2023-03-21 18:11 ` Vipin Sharma
2023-03-21 19:57 ` Sean Christopherson
2023-03-21 20:40 ` Sean Christopherson
2023-03-21 21:38 ` Sean Christopherson
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