linux-kernel - [PATCH 0/2] Protect vmstats on PREEMPT

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Message-Id: <20210723100034.13353-1-mgorman@techsingularity.net>
Date:   Fri, 23 Jul 2021 11:00:32 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Hugh Dickins <hughd@...gle.com>, Linux-MM <linux-mm@...ck.org>,
        Linux-RT-Users <linux-rt-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mel Gorman <mgorman@...hsingularity.net>
Subject: [PATCH 0/2] Protect vmstats on PREEMPT_RT

When adding local_lock support to mm/page_alloc.c and reducing the overhead
of vmstats in general, I wondered how vmstats could be safe on PREEMPT_RT
as it partially relies on interrupts being disabled for the stats that
must be accurate for correctness. As it turns out, the preempt-rt tree
already encountered the same problem.

This series protects just the primary counters. While there is another
vmstat-related patch, it is related to memcg getting using local_lock and
I have not fully considered those patches and whether they are ok as-is
or need modification but this series makes a start.

Patch 1 is authored by Thomas (cc'd) and has not being altered.

Patch 2 is authored by Ingo (cc'd) but I modified what he implemented
for reasons explained in the changelog.

This is specific to PREEMPT_RT which cannot be enabled on mainline yet
and should have no impact on !PREEMPT_RT kernels.

 include/linux/preempt.h | 18 +++++++++++++++++-
 mm/vmstat.c             | 12 ++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

-- 
2.26.2