From: Vlastimil Babka <vbabka@suse.cz>
To: Mel Gorman <mgorman@techsingularity.net>,
Andrew Morton <akpm@linux-foundation.org>
Cc: Nicolas Saenz Julienne <nsaenzju@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Michal Hocko <mhocko@kernel.org>, Hugh Dickins <hughd@google.com>,
Yu Zhao <yuzhao@google.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH 7/7] mm/page_alloc: Replace local_lock with normal spinlock
Date: Mon, 4 Jul 2022 16:39:57 +0200 [thread overview]
Message-ID: <ae15b692-bf68-51a8-1796-7ba15e156d2d@suse.cz> (raw)
In-Reply-To: <20220624125423.6126-8-mgorman@techsingularity.net>
On 6/24/22 14:54, Mel Gorman wrote:
> struct per_cpu_pages is no longer strictly local as PCP lists can be
> drained remotely using a lock for protection. While the use of local_lock
> works, it goes against the intent of local_lock which is for "pure
> CPU local concurrency control mechanisms and not suited for inter-CPU
> concurrency control" (Documentation/locking/locktypes.rst)
>
> local_lock protects against migration between when the percpu pointer is
> accessed and the pcp->lock acquired. The lock acquisition is a preemption
> point so in the worst case, a task could migrate to another NUMA node
> and accidentally allocate remote memory. The main requirement is to pin
> the task to a CPU that is suitable for PREEMPT_RT and !PREEMPT_RT.
>
> Replace local_lock with helpers that pin a task to a CPU, lookup the
> per-cpu structure and acquire the embedded lock. It's similar to local_lock
> without breaking the intent behind the API. It is not a complete API
> as only the parts needed for PCP-alloc are implemented but in theory,
> the generic helpers could be promoted to a general API if there was
> demand for an embedded lock within a per-cpu struct with a guarantee
> that the per-cpu structure locked matches the running CPU and cannot use
> get_cpu_var due to RT concerns. PCP requires these semantics to avoid
> accidentally allocating remote memory.
>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
-fix looks OK too
next prev parent reply other threads:[~2022-07-04 14:40 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-24 12:54 [PATCH v5 00/7] Drain remote per-cpu directly Mel Gorman
2022-06-24 12:54 ` [PATCH 1/7] mm/page_alloc: Add page->buddy_list and page->pcp_list Mel Gorman
2022-06-24 12:54 ` [PATCH 2/7] mm/page_alloc: Use only one PCP list for THP-sized allocations Mel Gorman
2022-06-24 12:54 ` [PATCH 3/7] mm/page_alloc: Split out buddy removal code from rmqueue into separate helper Mel Gorman
2022-06-24 12:54 ` [PATCH 4/7] mm/page_alloc: Remove mistaken page == NULL check in rmqueue Mel Gorman
2022-06-24 12:54 ` [PATCH 5/7] mm/page_alloc: Protect PCP lists with a spinlock Mel Gorman
2022-07-04 12:31 ` Vlastimil Babka
2022-07-05 7:20 ` Mel Gorman
2022-07-04 16:32 ` Nicolas Saenz Julienne
2022-06-24 12:54 ` [PATCH 6/7] mm/page_alloc: Remotely drain per-cpu lists Mel Gorman
2022-07-04 14:28 ` Vlastimil Babka
2022-06-24 12:54 ` [PATCH 7/7] mm/page_alloc: Replace local_lock with normal spinlock Mel Gorman
2022-06-24 18:59 ` Yu Zhao
2022-06-27 8:46 ` [PATCH] mm/page_alloc: Replace local_lock with normal spinlock -fix Mel Gorman
2022-07-04 14:39 ` Vlastimil Babka [this message]
2022-07-04 16:33 ` [PATCH 7/7] mm/page_alloc: Replace local_lock with normal spinlock Nicolas Saenz Julienne
2022-07-03 23:28 ` [PATCH v5 00/7] Drain remote per-cpu directly Andrew Morton
2022-07-03 23:31 ` Yu Zhao
2022-07-03 23:35 ` Andrew Morton
-- strict thread matches above, loose matches on Subject: below --
2022-06-13 12:56 [PATCH v4 " Mel Gorman
2022-06-13 12:56 ` [PATCH 7/7] mm/page_alloc: Replace local_lock with normal spinlock Mel Gorman
2022-06-15 22:43 ` Yu Zhao
[not found] ` <CGME20220615224855eucas1p1ea6d90c23ec9423dfe04b267f6dddd2a@eucas1p1.samsung.com>
2022-06-15 22:48 ` Marek Szyprowski
2022-06-15 23:04 ` Andrew Morton
2022-06-16 3:05 ` Yu Zhao
2022-06-17 7:55 ` Vlastimil Babka
2022-06-17 6:47 ` Marek Szyprowski
2022-06-21 9:21 ` Mel Gorman
2022-06-16 17:01 ` Vlastimil Babka
2022-06-16 21:07 ` Yu Zhao
2022-06-17 7:57 ` Vlastimil Babka
2022-06-21 9:27 ` Mel Gorman
2022-06-21 9:26 ` Mel Gorman
2022-06-17 9:39 ` Nicolas Saenz Julienne
2022-06-21 9:29 ` Mel Gorman
2022-06-21 9:31 ` Nicolas Saenz Julienne
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