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

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Message-ID: <20130103234558.GA1689@dcvr.yhbt.net>
Date:	Thu, 3 Jan 2013 23:45:58 +0000
From:	Eric Wong <normalperson@...t.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: ppoll() stuck on POLLIN while TCP peer is sending

Eric Wong <normalperson@...t.net> wrote:
> Eric Dumazet <eric.dumazet@...il.com> wrote:
> > With the following patch, I cant reproduce the 'apparent stuck'
> 
> Right, the output is just an approximation and the logic there
> was bogus.
> 
> Thanks for looking at this.

I'm still able to reproduce the issue under v3.8-rc2 with your patch
for toosleepy.

(As expected when blocked,) TCP send() will eventually return
ETIMEOUT when I forget to check (and toosleepy will abort from it)

I think this requires frequent dirtying/cycling of pages to reproduce.
(from copying large files around) to interact with compaction.
I'll see if I can reproduce the issue with read-only FS activity.

With 3.7.1 and compaction/THP disabled, I was able to run ~21 hours
and copy a few TB around without anything getting stuck.
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