Re: [PATCH 03/34] mm: Reduce the amount of work done when updating min_free_kbytes

Greg KH
2012-07-24T22:47:18Z

On Mon, Jul 23, 2012 at 02:38:16PM +0100, Mel Gorman wrote:
> commit 938929f14cb595f43cd1a4e63e22d36cab1e4a1f upstream.
>
> Stable note: Fixes https://bugzilla.novell.com/show_bug.cgi?id=726210 .
> Large machines with 1TB or more of RAM take a long time to boot
> without this patch and may spew out soft lockup warnings.

In comparing this with the upstream version, you have a few different
coding style differences, but no real content difference. Why?

>
> When min_free_kbytes is updated blocks marked MIGRATE_RESERVE are
> updated. Ordinarily, this work is unnoticable as it happens early
> in boot. However, on large machines with 1TB of memory, this can take
> a considerable time when NUMA distances are taken into account. The bulk
> of the work is done by pageblock_is_reserved() which examines the
> metadata for almost every page in the system. Currently, we are doing
> this far more than necessary as it is only required while there are
> still blocks to be marked MIGRATE_RESERVE. This patch significantly
> reduces the amount of work done by setup_zone_migrate_reserve()
> improving boot times on 1TB machines.
>
> [akpm@linux-foundation.org: coding-style fixes]

I'm guessing you didn't pick these up?

Anyway, I've taken it now as the original one from Linus's tree,
hopefully this doesn't burn me later in the series...

thanks,

greg k-h