Re: [patch v3 2/6] mm, compaction: return failed migration target pages back to freelist

[Andrew Morton]

On Tue, 6 May 2014 19:22:43 -0700 (PDT) David Rientjes <rientjes@xxxxxxxxxx> wrote:

> Memory compaction works by having a "freeing scanner" scan from one end of a 
> zone which isolates pages as migration targets while another "migrating scanner" 
> scans from the other end of the same zone which isolates pages for migration.
> 
> When page migration fails for an isolated page, the target page is returned to 
> the system rather than the freelist built by the freeing scanner.  This may 
> require the freeing scanner to continue scanning memory after suitable migration 
> targets have already been returned to the system needlessly.
> 
> This patch returns destination pages to the freeing scanner freelist when page 
> migration fails.  This prevents unnecessary work done by the freeing scanner but 
> also encourages memory to be as compacted as possible at the end of the zone.
> 
> Reported-by: Greg Thelen <gthelen@xxxxxxxxxx>

What did Greg actually report?  IOW, what if any observable problem is
being fixed here?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/