Re: [pve-devel] qemu + tcmalloc for rbd

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

Am 10/01/2024 um 10:12 schrieb Fiona Ebner:
> Am 09.01.24 um 18:02 schrieb DERUMIER, Alexandre:
>> Another way (maybe safer), is to build 2 binary in same package 
>> (/usr/bin/kvm-tcmalloc  && /usr/bin/kvm), and give option to user to
>> choose it.
>>
> 
> If we go for this route, I'd rather have two conflicting packages to
> avoid the redundant space usage for most people. Or if we really want to
> support being able to use both on a single system, an add-on kind of
> package with just the second binary.

I would like to avoid both, an extra package or an extra binary, as both
are a significant overhead for both us to maintain and user to work with.

Either tcmalloc works as allocator and is an actual improvement overall,
in which case we should unconditionally use it, or it doesn't work, or is
no improvement, in which case it makes no sense to expose it.

IME changing allocator is nice for some specific benchmarks, but overall
there often even are some regressions in other configurations..
We e.g. tested different allocators extensively when debugging some
memory growth during PBS backups, none of the shiny alternatives was
really any better, thus we resulted to triggering explicit trims.