From: Marcelo Tosatti <mtosatti@redhat.com>
To: Christoph Lameter <cl@gentwo.de>
Cc: Aaron Tomlin <atomlin@atomlin.com>,
Frederic Weisbecker <frederic@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 3/5] mm/vmstat: use cmpxchg loop in cpu_vm_stats_fold
Date: Thu, 2 Feb 2023 12:54:12 -0300 [thread overview]
Message-ID: <Y9vcpO5Dh2G3Y6ib@tpad> (raw)
In-Reply-To: <fb371ac-cf69-28a6-eca0-6caccda4e0b8@gentwo.de>
On Thu, Feb 02, 2023 at 03:38:58PM +0100, Christoph Lameter wrote:
> On Wed, 1 Feb 2023, Marcelo Tosatti wrote:
>
> > In preparation to switch vmstat shepherd to flush
> > per-CPU counters remotely, use a cmpxchg loop
> > instead of a pair of read/write instructions.
>
> You are mixing full atomic cmpxchg and per cpu atomic cmpxchg? That does
> not work.
OK, missing locked on the local functions. Can fix that.
> I thought you would only run this while the kernel is not active on the
> remote cpu? Then you dont need any cmpxchg and you can leave the function
> as is.
The remote cpu can enter kernel mode while this function executes.
There is no mode which indicates userspace cannot enter the kernel.
next prev parent reply other threads:[~2023-02-02 15:54 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-01 19:50 [PATCH 0/5] fold per-CPU vmstats remotely Marcelo Tosatti
2023-02-01 19:50 ` [PATCH 1/5] mm/vmstat: remove remote node draining Marcelo Tosatti
2023-02-01 19:50 ` [PATCH 2/5] mm/vmstat: switch counter modification to cmpxchg Marcelo Tosatti
2023-02-01 19:50 ` [PATCH 3/5] mm/vmstat: use cmpxchg loop in cpu_vm_stats_fold Marcelo Tosatti
2023-02-02 14:38 ` Christoph Lameter
2023-02-02 15:54 ` Marcelo Tosatti [this message]
2023-02-03 9:34 ` Christoph Lameter
2023-02-03 18:52 ` Marcelo Tosatti
2023-02-06 9:42 ` Christoph Lameter
2023-02-06 19:10 ` Marcelo Tosatti
2023-02-06 19:19 ` Matthew Wilcox
2023-02-01 19:50 ` [PATCH 4/5] mm/vmstat: switch vmstat shepherd to flush per-CPU counters remotely Marcelo Tosatti
2023-02-01 19:50 ` [PATCH 5/5] mm/vmstat: refresh stats remotely instead of via work item Marcelo Tosatti
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