From: Andrew Morton <akpm@linux-foundation.org>
To: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: steven.sistare@oracle.com, daniel.m.jordan@oracle.com,
mgorman@techsingularity.net, mgorman@suse.de, mhocko@suse.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1] mm: initialize pages on demand during boot
Date: Fri, 12 Jan 2018 15:37:34 -0800 [thread overview]
Message-ID: <20180112153734.1780ccc00ebced508fad397a@linux-foundation.org> (raw)
In-Reply-To: <20180112183405.22193-1-pasha.tatashin@oracle.com>
On Fri, 12 Jan 2018 13:34:05 -0500 Pavel Tatashin <pasha.tatashin@oracle.com> wrote:
> Deferred page initialization allows the boot cpu to initialize a small
> subset of the system's pages early in boot, with other cpus doing the rest
> later on.
>
> It is, however, problematic to know how many pages the kernel needs during
> boot. Different modules and kernel parameters may change the requirement,
> so the boot cpu either initializes too many pages or runs out of memory.
>
> To fix that, initialize early pages on demand. This ensures the kernel
> does the minimum amount of work to initialize pages during boot and leaves
> the rest to be divided in the multithreaded initialization path
> (deferred_init_memmap).
>
> The on-demand code is permanently disabled using static branching once
> deferred pages are initialized. After the static branch is changed to
> false, the overhead is up-to two branch-always instructions if the zone
> watermark check fails or if rmqueue fails.
Presumably this fixes some real-world problem which someone has observed?
Please describe that problem for us in lavish detail.
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next prev parent reply other threads:[~2018-01-12 23:37 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-12 18:34 [PATCH v1] mm: initialize pages on demand during boot Pavel Tatashin
2018-01-12 23:37 ` Andrew Morton [this message]
2018-01-24 19:40 ` Pavel Tatashin
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