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Date: Thu, 28 Sep 2006 17:17:06 -0700 From: Andrew Morton <akpm@...l.org> To: Roman Zippel <zippel@...ux-m68k.org> Cc: Dave Jones <davej@...hat.com>, Linux Kernel <linux-kernel@...r.kernel.org> Subject: Re: oom kill oddness. On Fri, 29 Sep 2006 01:03:16 +0200 (CEST) Roman Zippel <zippel@...ux-m68k.org> wrote: > Hi, > > On Wed, 27 Sep 2006, Dave Jones wrote: > > > So I have two boxes that are very similar. > > Both have 2GB of RAM & 1GB of swap space. > > One has a 2.8GHz CPU, the other a 2.93GHz CPU, both dualcore. > > > > The slower box survives a 'make -j bzImage' of a 2.6.18 kernel tree > > without incident. (Although it takes ~4 minutes longer than a -j2) > > > > The faster box goes absolutely nuts, oomkilling everything in sight, > > until eventually after about 10 minutes, the box locks up dead, > > and won't even respond to pings. > > > > Oh, the only other difference - the slower box has 1 disk, whereas the > > faster box has two in RAID0. I'm not surprised that stuff is getting > > oom-killed given the pathological scenario, but the fact that the > > box never recovered at all is a little odd. Does md lack some means > > of dealing with low memory scenarios ? > > I think I see the same thing on the other end on slow machines, here it > only takes a single compile job, which doesn't quite fit into memory and > another task (like top) which occasionally wakes up and tries to allocate > memory and then kills the compile job - that's very annoying. > > AFAICT the basic problem is that "did_some_progress" in __alloc_pages() is > rather local information, other processes can still make progress and keep > this process from making progress, which gets grumpy and starts killing. > What's happing here is that most memory is either mapped or in the swap > cache, so we have a race between processes trying to free memory from the > cache and processes mapping memory back into their address space. Kernel versions please, guys. There have been a lot of oom-killer changes post-2.6.18. > If someone wants to play with the problem, the example program below > triggers the problem relatively easily (booting with only little ram > helps), it starts a number of readers, which should touch a bit more > memory than is available and a few writers, which occasionally allocate > memory. > How much ram, how much swap? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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