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SubjectRe: [PATCH] mm: Reduce the amount of work done when updating min_free_kbytes
On Fri, 11 Nov 2011 16:21:19 +0000
Mel Gorman <mgorman@suse.de> wrote:

> When min_free_kbytes is updated, some pageblocks are marked MIGRATE_RESERVE.
> Ordinarily, this work is unnoticable as it happens early in boot but on
> large machines with 1TB of memory, this has been reported to delay
> boot times, probably due to the NUMA distances involved.
>
> The bulk of the work is due to calling calling pageblock_is_reserved()
> an unnecessary amount of times and accessing far more struct page
> metadata than is necessary. This patch significantly reduces the
> amount of work done by setup_zone_migrate_reserve() improving boot
> times on 1TB machines.
>

By how much? :)

(I mainly ask because I'm curious to know how long the kernel takes to
boot on a 1TB machine...)



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