Re: [libvirt] [PATCH 0/7] Add more options for IOThreads
On 09/15/2014 07:06 PM, Eric Blake wrote:
On 09/03/2014 10:15 AM, John Ferlan wrote:
> The following patches will add more support for IOThreads not completed
> from the initial patches. These changes support the remaining elements of
> bz https://bugzilla.redhat.com/show_bug.cgi?id=1101574 (working through
> unsetting the private bits - as there's nothing in there that should
> necessarily be private).
>
> Changes:
>
> 1. Add "--iothread" option to virsh attach-disk to allow using a specific
> iothread when attaching a disk
>
> 2. Add the ability to set CPU affinity for an IOThread. This involves
> multiple steps (patches 2-6) of adding the infrastructure to support
> setting scheduler affinity for the IOThread including cgroup setup.
> For the most part it's a "copy" of the vCPU pinning code, but
without
> the external interfaces - those will come at a later time after RHEL7.1.
>
> 3. Add to <cpuset/> a new element <iothreadpin iothread='#"
cpuset="string"/>
>
> NOTE: I can combine any/all of patches 2-6 - I just kept them separate
> so it wasn't a larger single patch.
>
> Although future changes will support API's and virsh commands to modify
> the iothreadpin, this set of changes at least is backportable to RHEL7.1
> since there are no external API changes.
>
> John Ferlan (7):
> virsh: Add iothread to 'attach-disk'
> qemu: Issue query-iothreads and to get list of active IOThreads
> vircgroup: Introduce virCgroupNewIOThread
> qemu_domain: Add niothreadpids and iothreadpids
Up to this patch, things worked for me,
Hmm... not sure what happened because I usually do go thru these one at
a time before sending them out - of course that was Sep 3 before my
brain was flooded with Coverity issues, so I don't quite remember
everthing I did. I think adding the cgroup code was something I did
last though since and figured I could rearrange things, but I guess I
failed to check if the rearranging worked.
In any case, the domain_conf.h from patch 7 should have been added
before/with "qemu_cgroup: Introduce cgroup functions for IOThreads"
Doing that resolves the build issue... and if I build/install from there
I can run the code below for the first patch, but not the second one.
The second one fails because of :
if (niothreads <= 0)
goto cleanup;
However, changing it to
+ if (niothreads < 0)
goto cleanup;
+ if (niothreads == 0)
+ return 0;
Now this is even more perplexing because I'm quite certain I tested the
path of starting a guest without iothreads configured, but apparently
that doesn't seem to be the case.
Patches coming...
<sigh>
John
> qemu_cgroup: Introduce cgroup functions for IOThreads
> qemu: Allow pinning specific IOThreads to a CPU
but with these two patches, I get a compilation failure:
qemu/qemu_cgroup.c: In function 'qemuSetupCgroupForIOThreads':
qemu/qemu_cgroup.c:1160:41: error: 'struct <anonymous>' has no member
named 'niothreadspin'
for (j = 0; j < def->cputune.niothreadspin; j++) {
^
> domain_conf: Add iothreadpin to cputune
and with this patch, I'm now unable to start a transient domain, with a
less-than-stellar message:
$ qemu-img create -f qcow2 -o compat=0.10 base.img 10M
$ virsh create /dev/stdin <<EOF
<domain type='kvm'>
<name>testvm1</name>
<memory unit='MiB'>256</memory>
<vcpu>1</vcpu>
<os>
<type arch='x86_64'>hvm</type>
</os>
<devices>
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2'/>
<source file='$PWD/base.img'/>
<target dev='vda' bus='virtio'/>
</disk>
<graphics type='vnc'/>
</devices>
</domain>
EOF
error: Failed to create domain from /dev/stdin
error: An error occurred, but the cause is unknown
Normally, that command starts up a guest (yeah, the guest is doing
nothing but wasting CPU cycles, because it has a blank disk, but it's a
great little smoke test for my recent work in block jobs)
Sounds like this smoke test needs to be added to the list of make check
tests somehow...