Bug#519586: linux-image-2.6.26-1-xen-amd64: Huge "Slab Unreclaimable" and continually growing
On Fri, Mar 13, 2009 at 11:22:58AM -0600, Daniel Fussell wrote:
> Package: linux-image-2.6.26-1-xen-amd64
> Severity: critical
> Justification: breaks unrelated software
>
> After ~4 days running a high-load Samba server in a domU with 1G memory,
> SUnreclaim grows to over 700MB, dropping samba performance from ~60MB/s
> transfers to 2MB/s transfers. Appears to also be a problem with stock
> linux-image-2.6.26-1-amd kernel as well, as tested from a physical
> machine w/ 4G memory and 4 Opterons, though it takes longer to fill the
> memory and degrade performance. 'xm mem-set'-ing the domU to 2G memory
> recovers some performance (not all), and slab unreclaimable continues to
> grow.
>
> I've tested with Lenny and Samba versions 3.2.5 (lenny), 3.3.0
> (experimental), and 3.0.23c (compiled from upstream) in a domU, and
> 3.3.0 (experimental) on the physical machine. I have one other
> pre-production Lenny domU running apache that is not showing the
> cancerous slab growth; but it is pre-production and not taking nearly
> the same load as the samba servers.
>
> slabtop shows most of the slabs consumed by size-128 (~1.4M objects
> using ~160MB) and size-256 (~1.4M objects using ~360M)
>
> /boot/config-2.6.26-1-xen-amd64 show SLAB as the allocator in the xen
> and non-xen kernels. I'm currently compiling with SLUB on a xen kernel
> to see if it resolves the issue. Both machine's meminfo and procinfo
> are attached.
How did the tests with the SLUB allocator go?
Cheers,
Moritz
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