[pve-devel] applied: [RFC pve-qemu] disable jemalloc
Alexandre.DERUMIER at groupe-cyllene.com
Fri Mar 10 19:05:29 CET 2023
sorry for bumping this old thread.
I'm currently benching again qemu with librbd and memory allocator.
It's seem that they are still performance problem with default glibc
allocator, around 20-25% less iops and bigger latency.
From my bench, i'm around 60k iops vs 80-90k iops with 4k randread.
Redhat have also notice it
I known than jemalloc was buggy with rust lib && pbs block driver,
but did you have evaluated tcmalloc ?
Note that it's possible to load it dynamically with LD_PRELOAD,
so maybe could we add an option in vm config to enable it ?
Le mardi 15 décembre 2020 à 14:43 +0100, Thomas Lamprecht a écrit :
> On 10.12.20 16:23, Stefan Reiter wrote:
> > jemalloc does not play nice with our Rust library (proxmox-backup-
> > qemu),
> > specifically it never releases memory allocated from Rust to the
> > OS.
> > This leads to a problem with larger caches (e.g. for the PBS block
> > driver).
> > It appears to be related to this GitHub issue:
> > https://github.com/jemalloc/jemalloc/issues/1398
> > The background_thread solution seems weirdly hacky, so let's
> > disable
> > jemalloc entirely for now.
> > Signed-off-by: Stefan Reiter <s.reiter at proxmox.com>
> > ---
> > @Alexandre: you were the one to introduce jemalloc into our QEMU
> > builds a long
> > time ago - does it still provide a measurable benefit? If the
> > performance loss
> > would be too great in removing it, we could maybe figure out some
> > workarounds as
> > well.
> > Its current behaviour does seem rather broken to me though...
> > debian/rules | 1 -
> > 1 file changed, 1 deletion(-)
> applied, thanks!
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