Re: [PATCH 61 of 66] use compaction for GFP_ATOMIC order > 0

KOSAKI Motohiro
2010-11-09T10:27:44Z

> From: Andrea Arcangeli <aarcange@redhat.com>
>
> This takes advantage of memory compaction to properly generate pages of order >
> 0 if regular page reclaim fails and priority level becomes more severe and we
> don't reach the proper watermarks.
>
> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>

First, I don't think this patch is related to GFP_ATOMIC. So, I think the
patch title is a bit misleading.

Second, this patch has two changes. 1) remove PAGE_ALLOC_COSTLY_ORDER
threshold 2) implement background compaction. please separate them.

Third, This patch makes a lot of PFN order page scan and churn LRU
aggressively. I'm not sure this aggressive lru shuffling is safe and
works effective. I hope you provide some demonstration and/or show
benchmark result.

Thanks.