From: Johannes Weiner <hannes@cmpxchg.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>, John Dias <joaodias@google.com>,
Tim Murray <timmurray@google.com>,
Matthew Wilcox <willy@infradead.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Martin Liu <liumartin@google.com>
Subject: Re: [PATCH v3] mm: don't be stuck to rmap lock on reclaim path
Date: Tue, 10 May 2022 14:16:07 -0400 [thread overview]
Message-ID: <Ynqr57CVLPOqwhZa@cmpxchg.org> (raw)
In-Reply-To: <20220510171100.48500-1-minchan@kernel.org>
Hi Minchan,
The patch looks reasonable to me, but one thing stands out:
On Tue, May 10, 2022 at 10:11:00AM -0700, Minchan Kim wrote:
> @@ -1391,6 +1391,10 @@ static enum page_references folio_check_references(struct folio *folio,
> if (vm_flags & VM_LOCKED)
> return PAGEREF_ACTIVATE;
>
> + /* page_referenced didn't work due to lock contention */
> + if (referenced_ptes == -1)
> + return PAGEREF_KEEP;
> +
> if (referenced_ptes) {
> /*
> * All mapped folios start out with page table
This means contended inactive pages get rotated.
> @@ -2492,7 +2496,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
> }
>
> if (folio_referenced(folio, 0, sc->target_mem_cgroup,
> - &vm_flags)) {
> + &vm_flags) > 0) {
> /*
> * Identify referenced, file-backed active pages and
> * give them one more trip around the active list. So
This means contended active pages do NOT get rotated.
It's a bit of an arbitrary choice what to do with reclaim candidates
for which you can get no reference information, but staying consistent
is likely a good idea. My preference would be to just rotate contended
pages throughout rather than risk dropping the workingset on the floor.
/* Referenced or rmap lock contention: rotate */
if (folio_referenced() != 0) {
...
What do you think?
next prev parent reply other threads:[~2022-05-10 18:17 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-10 17:11 [PATCH v3] mm: don't be stuck to rmap lock on reclaim path Minchan Kim
2022-05-10 18:16 ` Johannes Weiner [this message]
2022-05-10 21:44 ` Minchan Kim
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