Subject: Re: scheduler went mad?
To: Valdis.Kletnieks@vt.edu
Date: Thu, 12 Apr 2001 16:12:55 +0100 (BST)
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <200104121457.f3CEv8o09656@foo-bar-baz.cc.vt.edu> from "Valdis.Kletnieks@vt.edu" at Apr 12, 2001 10:57:08 AM
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Message-Id: <E14nimI-0000oY-00@the-village.bc.nu>
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Sender: linux-kernel-owner@vger.kernel.org

> I've seen the same scenario about 2-3 times a week.  kswapd and one or
> more processes all CPU bound, totalling to 100%.  I've had 'esdplay' hung
> on several occasions, and 2-3 times it's been xscreensaver (3.29) hung.
> The 'hung' processes are consistently immune to kill -9, even as root, which
> indicates to me that they're hung inside a kernel call or something.

Do you have > 800Mb of RAM ?

> In page_alloc.c, __alloc_pages() has a 'goto try_again;' which will
> cause it to loop around and try to get more memory.  I'm wondering if

Even outside of that certain drivers also loop on alloc failures as does 
TCP.

> would explain the high context-switch rate.  I'm not clear on how kswapd
> can end up getting stuck and failing to free up something - unless it ends
> up calling __alloc_pages itself indirectly and the PF_MEMALLOC bit isn't
> enough to get it the memory it needs, causing a deadlock/loop between
> kswapd and __alloc_pages/wakeup_kswapd().

bounce buffers for one

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