About this list Date view Thread view Subject view Author view Attachment view

From: Liam Helmer (linuxlists_at_thevenue.org)
Date: Tue 05 Oct 2004 - 19:43:34 BST

I've actually been trying to track down a bug with 2.6.8(.1), vserver
1.9.2, and squashfs. I'm getting a page allocation failure as well, and
and occasional (temporary until reboot) corruption of a squashfs
filesystem. I was trying to track it down with Philip, who built

The basic issue is that after allocating a lot of cache to a squashfs
filesystem, the filesystem is unable to allocate any more RAM to new
squashfs filesystems. It's basically acting as though it's running out
of allocatable kernel memory (which squashfs has to allocate in in 64k
continuous chunks). His suggestion was that it was a case of high memory
fragmentation. However, this was on a box with 512MB of RAM, after
running it in maintenance mode (without any running processes), and
simply filling up the cache. I was getting a page allocation, order 4,
at this point.

Herbert: Is there anything about the way that memory is allocated in
vserver, especially when caching data from disk (or, potentially, from
the network, as we're seeing here) that prevents that memory from being
re:used elsewhere? I remember you fixed an in 1.9.1rc4 where filesystem
cache for squashfs was being marked for a particular XID, and thus if a
file was first accessed in a vserver, then other vservers were unable to
use that file. Could there be anything similar here?

Here's the oops that I'm getting:

mount: page allocation failure. order:4, mode:0xd0
 [<c0141153>] __alloc_pages+0x243/0x350
 [<c014127f>] __get_free_pages+0x1f/0x40
 [<c014448f>] kmem_getpages+0x1f/0xd0
 [<c014501a>] cache_grow+0xaa/0x160
 [<c0145236>] cache_alloc_refill+0x166/0x210
 [<c01456a7>] __kmalloc+0x67/0x90
 [<c01e9a0b>] squashfs_fill_super+0x69b/0xbe0
 [<c025f1d9>] snprintf+0x19/0x20
 [<c0190c91>] disk_name+0x71/0x80
 [<c015ffd0>] get_sb_bdev+0xf0/0x130
 [<c0140fcf>] __alloc_pages+0xbf/0x350
 [<c0141163>] __alloc_pages+0x253/0x350
 [<c01eb90e>] squashfs_get_sb+0x1e/0x30
 [<c01e9370>] squashfs_fill_super+0x0/0xbe0
 [<c01601e8>] do_kern_mount+0x88/0x170
 [<c01760dd>] do_new_mount+0x9d/0xe0
 [<c01767d7>] do_mount+0x187/0x1e0
 [<c0141163>] __alloc_pages+0x253/0x350
 [<c026002e>] copy_from_usother er+0x3e/0x70
 [<c01765fc>] copy_mount_options+0x4c/0xa0
 [<c0176bbf>] sys_mount+0x9f/0x130
 [<c0105e77>] syscall_call+0x7/0xb
SQUASHFS error: Failed to allocate read_page block


On Tue, 2004-10-05 at 19:16 +0200, Yann.Dupont wrote:
> Herbert Poetzl wrote:
> >
> >depends on the hardware, and of course on the usage pattern,
> >because one instance of postfix will not cause _any_ memory
> >pressure on a typical system ...
> >
> >
> >
> Yes. The other machine with 2.6 kernel also have vservers but with much
> lighter usage
> >>Is there a chance there are allocations on vserver code that can affect
> >>this ?
> >>
> >>
> >
> >sure, and it might even be the cause (especially because
> >it for sure adds to the memory pressure) ...
> >
> >
> Ok, so do you think vserver IS the culprit, because of a bug in vserver
> 2.6 memory allocation code, Or (much more probable)
> vserver just triggers the bug because the vservers, in a cumulative
> effect are BIG consummer of memory ?
> In that case, vserver is not the bug owner, it's the 2.6 kernel in
> itself that have defficiencies in that case...
> Maybe time to buy an opteron system :) Or just see the 2G/2G option I
> already seen discussed in linux kernel mailing lists...
> And posting in linux kernel mailing list.
> Thanks for your response...
> Oh, btw, You may be interrested by the fact we have now more than 100
> vservers deployed... Thanks again (you & others) for this
> very nice piece of software...

Liam Helmer <linuxlists_at_thevenue.org>

_______________________________________________ Vserver mailing list Vserver_at_list.linux-vserver.org http://list.linux-vserver.org/mailman/listinfo/vserver

About this list Date view Thread view Subject view Author view Attachment view
[Next/Previous Months] [Main vserver Project Homepage] [Howto Subscribe/Unsubscribe] [Paul Sladen's vserver stuff]
Generated on Tue 05 Oct 2004 - 19:43:54 BST by hypermail 2.1.3