Messages in this thread | | | Date | Fri, 30 Apr 2010 05:52:38 +0200 (CEST) | From | Mikulas Patocka <> | Subject | Re: swapping when there's a free memory |
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On Tue, 27 Apr 2010, KAMEZAWA Hiroyuki wrote:
> On Mon, 26 Apr 2010 15:33:33 -0700 > Andrew Morton <akpm@linux-foundation.org> wrote: > > > On Sun, 25 Apr 2010 09:13:49 +0200 > > Pavel Machek <pavel@ucw.cz> wrote: > > > > > Hi! > > > > > > > I captured this output of vmstat. The machine was freeing cache and > > > > swapping out pages even when there was a plenty of free memory. > > > > > > > > The machine is sparc64 with 1GB RAM with 2.6.34-rc4. This abnormal > > > > swapping happened during running spadfsck --- a fsck program for a custom > > > > filesystem that caches most reads in its internal cache --- so it reads > > > > buffers and allocates memory at the same time. > > > > > > > > Note that sparc64 doesn't have any low/high memory zones, so it couldn't > > > > be explained by filling one zone and needing to allocate pages in it. > > > > > > Fragmented memory + high-order allocation? > > > > Yeah, could be. I wonder which slab/slub/slob implementation you're > > using, and what page sizes it uses for dentries, inodes, etc. Can you > > have a poke in /prob/slabinfo?
It uses one page-per-slab for dentries and two for inodes. But there was certainly no dentry or inode-based load --- the machine runs without X with minimum daemons, there is no major background work. There was just a process reading 128-kbyte blocks from a raw device and caching them in its userspace that triggered this. Can it be that kernel uses high-order allocations for reading from a buffer cache?
> And please /proc/buddyinfo and /proc/zoneinfo when the system is swappy.
It happens rarely, I don't know if I catch it at the right time. The report I sent, was what I found in a scrollback of vmstat. I didn't catch it in real time.
> Thanks, > -Kame
Mikulas
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