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Reply-To: "Hillf Danton" <hillf.zj@alibaba-inc.com>
From: "Hillf Danton" <hillf.zj@alibaba-inc.com>
To: "'Tetsuo Handa'" <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: "Linus Torvalds" <torvalds@linux-foundation.org>,
        "Michal Hocko" <mhocko@kernel.org>,
        "David Rientjes" <rientjes@google.com>,
        "Johannes Weiner" <hannes@cmpxchg.org>,
        "linux-kernel" <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>
Subject: Re: Silent hang up caused by pages being not scanned?
Date: Wed, 14 Oct 2015 16:03:15 +0800
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> > 
> > In particular, I think that you'll find that you will have to change
> > the heuristics in __alloc_pages_slowpath() where we currently do
> > 
> >         if ((did_some_progress && order <= PAGE_ALLOC_COSTLY_ORDER) || ..
> > 
> > when the "did_some_progress" logic changes that radically.
> > 
> 
> Yes. But we can't simply do
> 
>	if (order <= PAGE_ALLOC_COSTLY_ORDER || ..
> 
> because we won't be able to call out_of_memory(), can we?
>
Can you please try a simplified retry logic?

thanks
Hillf
--- a/mm/page_alloc.c	Wed Oct 14 14:45:28 2015
+++ b/mm/page_alloc.c	Wed Oct 14 15:43:31 2015
@@ -3154,8 +3154,7 @@ retry:
 
 	/* Keep reclaiming pages as long as there is reasonable progress */
 	pages_reclaimed += did_some_progress;
-	if ((did_some_progress && order <= PAGE_ALLOC_COSTLY_ORDER) ||
-	    ((gfp_mask & __GFP_REPEAT) && pages_reclaimed < (1 << order))) {
+	if (did_some_progress) {
 		/* Wait for some write requests to complete then retry */
 		wait_iff_congested(ac->preferred_zone, BLK_RW_ASYNC, HZ/50);
 		goto retry;
--