linux-kernel - Re: ppoll() stuck on POLLIN while TCP peer is sending

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Date:	Thu, 10 Jan 2013 09:25:11 +0000
From:	Eric Wong <normalperson@...t.net>
To:	Mel Gorman <mgorman@...e.de>
Cc:	linux-mm@...ck.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan@...nel.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: ppoll() stuck on POLLIN while TCP peer is sending

Mel Gorman <mgorman@...e.de> wrote:
> page->pfmemalloc can be left set for captured pages so try this but as
> capture is rarely used I'm strongly favouring a partial revert even if
> this works for you. I haven't reproduced this using your workload yet
> but I have found that high-order allocation stress tests for 3.8-rc2 are
> completely screwed. 71% success rates at rest in 3.7 and 6% in 3.8-rc2 so
> I have to chase that down too.
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 9d20c13..c242d21 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2180,8 +2180,10 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
>  	current->flags &= ~PF_MEMALLOC;
>  
>  	/* If compaction captured a page, prep and use it */
> -	if (page && !prep_new_page(page, order, gfp_mask))
> +	if (page && !prep_new_page(page, order, gfp_mask)) {
> +		page->pfmemalloc = false;
>  		goto got_page;
> +	}
>  
>  	if (*did_some_progress != COMPACT_SKIPPED) {
>  		/* Page migration frees to the PCP lists but we want merging */

This (on top of your previous patch) seems to work great after several
hours of testing on both my VM and real machine.  I haven't tried your
partial revert, yet.  Will try that in a bit on the VM.
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