From: Christoph Lameter <cl@gentwo.de>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: linux-kernel@vger.kernel.org, Nitesh Lal <nilal@redhat.com>,
Nicolas Saenz Julienne <nsaenzju@redhat.com>,
Frederic Weisbecker <frederic@kernel.org>,
Juri Lelli <juri.lelli@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Alex Belits <abelits@belits.com>, Peter Xu <peterx@redhat.com>
Subject: Re: [patch V3 5/8] task isolation: sync vmstats conditional on changes
Date: Wed, 25 Aug 2021 11:46:12 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.22.394.2108251143270.317806@gentwo.de> (raw)
In-Reply-To: <20210824152646.822271769@fuller.cnet>
On Tue, 24 Aug 2021, Marcelo Tosatti wrote:
> Rather than syncing VM-stats on every return to userspace
> (or VM-entry), keep track of changes through a per-CPU bool.
>
> This improves performance when enabling task isolated
> for vcpu VMs.
And it adds overhead for each time the counters are updated. The static
check is not that bad but the per cpu reference causes an extra cacheline
hit in potentially performance sensitive vm code.
On the other hand: Once we have an indicator that the vmstats have been
updated then the checks for the need to perform a vmstat update can be
simplified using that percpu variable and made much faster.
next prev parent reply other threads:[~2021-08-25 9:46 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-24 15:24 [patch V3 0/8] extensible prctl task isolation interface and vmstat sync Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 1/8] add basic task isolation prctl interface Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 2/8] add prctl task isolation prctl docs and samples Marcelo Tosatti
2021-08-26 9:59 ` Frederic Weisbecker
2021-08-26 12:11 ` Marcelo Tosatti
2021-08-26 19:15 ` Christoph Lameter
2021-08-26 20:37 ` Marcelo Tosatti
2021-08-27 13:08 ` Frederic Weisbecker
2021-08-27 14:44 ` Marcelo Tosatti
2021-08-30 11:38 ` Frederic Weisbecker
2021-09-01 13:11 ` Nitesh Lal
2021-09-01 17:34 ` Marcelo Tosatti
2021-09-01 17:49 ` Nitesh Lal
2021-08-24 15:24 ` [patch V3 3/8] task isolation: sync vmstats on return to userspace Marcelo Tosatti
2021-09-10 13:49 ` nsaenzju
2021-08-24 15:24 ` [patch V3 4/8] procfs: add per-pid task isolation state Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 5/8] task isolation: sync vmstats conditional on changes Marcelo Tosatti
2021-08-25 9:46 ` Christoph Lameter [this message]
2021-08-24 15:24 ` [patch V3 6/8] KVM: x86: call isolation prepare from VM-entry code path Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 7/8] mm: vmstat: move need_update Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 8/8] mm: vmstat_refresh: avoid queueing work item if cpu stats are clean Marcelo Tosatti
2021-08-25 9:30 ` Christoph Lameter
2021-09-01 13:05 ` Nitesh Lal
2021-09-01 17:32 ` Marcelo Tosatti
2021-09-01 18:33 ` Marcelo Tosatti
2021-09-03 17:38 ` Nitesh Lal
2021-08-25 10:02 ` [patch V3 0/8] extensible prctl task isolation interface and vmstat sync Marcelo Tosatti
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