From: Christoph Lameter <cl@gentwo.de>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Frederic Weisbecker <frederic@kernel.org>,
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: Mon, 16 Jan 2023 10:51:40 +0100 (CET) [thread overview]
Message-ID: <24ca2aad-54b2-2c3a-70b5-49a33c9a33@gentwo.de> (raw)
In-Reply-To: <Y77s4x5yC4O1OxTQ@tpad>
On Wed, 11 Jan 2023, Marcelo Tosatti wrote:
> OK, can replace this_cpu operations with this_cpu_ptr + standard C operators
> (and in fact can do that for interrupt disabled functions as well, that
> is CONFIG_HAVE_CMPXCHG_LOCAL not defined).
>
> Is that it?
No that was hyperthetical.
I do not know how to get out of this dilemma. We surely want to keep fast
vmstat operations working.
The fundamental issue that causes the vmstat discrepancies is likely that
the fast this_cpu ops can increment the counter on any random cpu and that
this is the reason you get vmstat discrepancies.
Give up the assumption that an increment of a this_cpu counter on a
specific cpu means that something occurred on that specific cpu. Maybe
that will get you on a path to resolve the issues you are seeing.
next prev parent reply other threads:[~2023-01-16 9:53 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
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 [this message]
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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