[pve-devel] pve-devel Digest, Vol 60, Issue 45

[Stanislav German-Evtushenko]

> Message: 9
> Date: Thu, 28 May 2015 17:47:54 +0200 (CEST)
> From: Dietmar Maurer <dietmar at proxmox.com>
> To: Stanislav German-Evtushenko <ginermail at gmail.com>
> Cc: pve-devel <pve-devel at pve.proxmox.com>
> Subject: Re: [pve-devel] Default cache mode for VM hard drives
> Message-ID:
>         <851217848.227.1432828074143.JavaMail.open-xchange at ronja.mits.lan>
> Content-Type: text/plain; charset=UTF-8
>
>> > But there is currently only one io-thread in qemu, so this
>> > cannot happen with qemu if above is the only problem?
>>
>> But there are other threads, right? Buffer can be changed by another
>> thread where guest OS itself is running.
>
> No, AFAIK there is only one thread doing all IO (currently). But it
> is using async IO with coroutines - maybe that can also trigger the
> problem?
>

Please have a look:

root at virt1:~# for pid in $(pidof kvm); do echo "threads of $pid $(ps
-o nlwp $pid | tail -1)"; done
threads of 900883    6
threads of 606008    5
threads of 524867    4
threads of 524750    5
threads of 524550    7
threads of 521471    8
threads of 520324    4
threads of 519520    3
threads of 518997    4
threads of 152071    4
threads of 9029    3
threads of 8874    4
threads of 8695    3
threads of 8471    3

root at virt1:~# for pid in $(pidof kvm); do echo "threads of $pid $(ps
-o nlwp $pid | tail -1)"; done
threads of 900883    6
threads of 606008    5
threads of 524867    4
threads of 524750    5
threads of 524550    7
threads of 521471    5
threads of 520324    4
threads of 519520    3
threads of 518997    3
threads of 152071    4
threads of 9029    4
threads of 8874    3
threads of 8695    3
threads of 8471    3

Each kvm process have multiple threads and the number of them is
changing in time.

Stanislav