From: Frederic Weisbecker <frederic@kernel.org>
To: Christoph Lameter <cl@gentwo.de>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
atomlin@atomlin.com, tglx@linutronix.de, mingo@kernel.org,
peterz@infradead.org, pauld@redhat.com, neelx@redhat.com,
oleksandr@natalenko.name, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH v13 2/6] mm/vmstat: Use vmstat_dirty to track CPU-specific vmstat discrepancies
Date: Tue, 10 Jan 2023 13:18:46 +0100 [thread overview]
Message-ID: <Y71XpnJGumySL9ej@lothringen> (raw)
In-Reply-To: <b89a9828-d4e-9874-d482-dbb6cbe46@gentwo.de>
On Tue, Jan 10, 2023 at 01:06:37PM +0100, Christoph Lameter wrote:
> On Thu, 5 Jan 2023, Marcelo Tosatti wrote:
> > @@ -577,6 +579,9 @@ static inline void mod_zone_state(struct
> > s8 __percpu *p = pcp->vm_stat_diff + item;
> > long o, n, t, z;
> >
> > + /* cmpxchg and vmstat_mark_dirty should happen on the same CPU */
> > + preempt_disable();
>
> If you are disabling preemption then why do we still need cmpxchg?
> Same again below.
Note I'm absolutely clueless with vmstat. But I was wondering about it as well
while reviewing Marcelo's series, so git blame pointed me to:
7c83912062c801738d7d19acaf8f7fec25ea663c ("vmstat: User per cpu atomics to avoid
interrupt disable / enable")
And this seem to mention that this can race with IRQs as well, hence the local
cmpxchg operation.
next prev parent reply other threads:[~2023-01-10 12:18 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-05 12:52 [PATCH v13 0/6] Ensure quiet_vmstat() is called when returning to userpace and when idle tick is stopped Marcelo Tosatti
2023-01-05 12:52 ` [PATCH v13 1/6] mm/vmstat: Add CPU-specific variable to track a vmstat discrepancy Marcelo Tosatti
2023-01-10 11:58 ` Christoph Lameter
2023-01-10 12:12 ` Frederic Weisbecker
2023-01-05 12:52 ` [PATCH v13 2/6] mm/vmstat: Use vmstat_dirty to track CPU-specific vmstat discrepancies Marcelo Tosatti
2023-01-10 12:06 ` Christoph Lameter
2023-01-10 12:18 ` Frederic Weisbecker [this message]
2023-01-10 13:39 ` Christoph Lameter
2023-01-10 20:09 ` Marcelo Tosatti
2023-01-11 8:42 ` Christoph Lameter
2023-01-11 17:07 ` Marcelo Tosatti
2023-01-16 9:51 ` Christoph Lameter
2023-01-16 16:11 ` Marcelo Tosatti
2023-01-17 12:52 ` Christoph Lameter
2023-01-05 12:52 ` [PATCH v13 3/6] mm/vmstat: manage per-CPU stats from CPU context when NOHZ full Marcelo Tosatti
2023-01-05 12:52 ` [PATCH v13 4/6] tick/nohz_full: Ensure quiet_vmstat() is called on exit to user-mode when the idle tick is stopped Marcelo Tosatti
2023-01-05 12:52 ` [PATCH v13 5/6] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too Marcelo Tosatti
2023-01-05 12:52 ` [PATCH v13 6/6] mm/vmstat: avoid queueing work item if cpu stats are clean Marcelo Tosatti
[not found] ` <20230106001244.4463-1-hdanton@sina.com>
2023-01-06 12:51 ` [PATCH v13 3/6] mm/vmstat: manage per-CPU stats from CPU context when NOHZ full Marcelo Tosatti
2023-01-06 15:01 ` Hillf Danton
2023-01-06 18:16 ` Marcelo Tosatti
2023-01-07 0:15 ` Hillf Danton
2023-01-09 14:12 ` Marcelo Tosatti
2023-01-10 2:43 ` Hillf Danton
2023-01-10 11:50 ` Marcelo Tosatti
2023-01-10 15:19 ` Hillf Danton
2023-01-10 16:12 ` Frederic Weisbecker
2023-01-10 23:58 ` Hillf Danton
2023-01-11 0:09 ` Frederic Weisbecker
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