From: Johannes Weiner <hannes@cmpxchg.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Hillf Danton <hdanton@sina.com>,
Mel Gorman <mgorman@techsingularity.net>,
linux-mm@kvack.org, Minchan Kim <minchan@kernel.org>,
Yang Shi <yang.shi@linux.alibaba.com>
Subject: Re: [PATCH] mm: vmscan: Add warn on inadvertently reclaiming mapped page
Date: Wed, 29 May 2019 13:01:44 -0400 [thread overview]
Message-ID: <20190529170144.GA30884@cmpxchg.org> (raw)
In-Reply-To: <20190528212257.f795b405ac1b88d72bb3fa2f@linux-foundation.org>
On Tue, May 28, 2019 at 09:22:57PM -0700, Andrew Morton wrote:
> On Sun, 26 May 2019 14:23:53 +0800 Hillf Danton <hdanton@sina.com> wrote:
>
> > In the function isolate_lru_pages(), we check scan_control::may_unmap and set
> > isolation mode accordingly in order to not isolate from the lru list any page
> > that does not match the isolation mode. For example, we should skip all sill
> > mapped pages if isolation mode is set to be ISOLATE_UNMAPPED.
> >
> > So complain, while scanning the isolated pages, about the very unlikely event
> > that we hit a mapped page that we should never have isolated. Note no change
> > is added in the current scanning behavior without VM debug configured.
>
> The patch is inoffensive enough, but one wonders what inspired it. Do
> you have reason to believe that this will trigger?
I don't think this patch makes sense.
There isn't anything preventing someone from mapping the page between
the LRU isolation and shrink_page_list(). The isolation filter is only
an optimization to reduce unnecessary LRU churn, not a guarantee.
prev parent reply other threads:[~2019-05-29 17:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190526062353.14684-1-hdanton@sina.com>
2019-05-27 7:42 ` [PATCH] mm: vmscan: Add warn on inadvertently reclaiming mapped page Yang Shi
2019-05-29 4:22 ` Andrew Morton
2019-05-29 17:01 ` Johannes Weiner [this message]
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