[libvirt] [PATCH v4 0/2] Add support for qcow2 cache

[Liu Qing]

On Wed, Sep 13, 2017 at 06:51:35AM -0400, John Ferlan wrote:
> 
> 
> On 09/13/2017 05:21 AM, Liu Qing wrote:
> > Qcow2 small IO random write performance will drop dramatically if the l2
> > cache table could not cover the whole disk. This will be a lot of l2
> > cache table RW operations if cache miss happens frequently.
> >  
> > This patch exports the qcow2 driver parameter
> > l2-cache-size/refcount-cache-size, first added in Qemu 2.2, and
> > cache-clean-interval, first added in Qemu 2.5, in libvirt.
> > 
> > Change since v3: a) copy qcow2 cache configurion from source to backing
> >                     to backing file source.
> 
> 
> The difference you list doesn't make any sense. The only difference
> between this an V3 is removing the qemu_command.c from patch1.  I did a
> git diff between the two trees I have from your patches:
> 
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index c3b81e138..e95683965 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -14318,11 +14318,6 @@
> qemuDomainSnapshotDiskDataCollect(virQEMUDriverPtr driver,
>          if (!(dd->src = virStorageSourceCopy(snap->def->disks[i].src,
> false)))
>              goto error;
> 
> -        /* keep the qcow2 cache configuration */
> -        dd->src->l2_cache_size = vm->def->disks[i]->src->l2_cache_size;
> -        dd->src->refcount_cache_size =
> vm->def->disks[i]->src->refcount_cache_size;
> -        dd->src->cache_clean_interval =
> vm->def->disks[i]->src->cache_clean_interval;
If these three lines are not added, the qcow2 element(child of driver
element) will be missed after a external disk snapshot. This is due to the
values of the three parameters will be set to 0.
> -
>          if (virStorageSourceInitChainElement(dd->src, dd->disk->src,
> false) < 0)
>              goto error;
> 
> 
> I'll stick with the v3 version and adjustments from comments that I made.
> 
> John
> > Liu Qing (2):
> >   conf, docs: Add qcow2 cache configuration support
> >   qemu: add capability checking for qcow2 cache configuration
> > 
> >  docs/formatdomain.html.in                          | 43 ++++++++++
> >  docs/schemas/domaincommon.rng                      | 35 ++++++++
> >  src/conf/domain_conf.c                             | 95 +++++++++++++++++++++-
> >  src/qemu/qemu_capabilities.c                       |  9 ++
> >  src/qemu/qemu_capabilities.h                       |  3 +
> >  src/qemu/qemu_command.c                            | 33 ++++++++
> >  src/qemu/qemu_driver.c                             |  5 ++
> >  src/util/virstoragefile.c                          |  3 +
> >  src/util/virstoragefile.h                          |  6 ++
> >  tests/qemucapabilitiesdata/caps_2.5.0.x86_64.xml   |  3 +
> >  .../caps_2.6.0-gicv2.aarch64.xml                   |  3 +
> >  .../caps_2.6.0-gicv3.aarch64.xml                   |  3 +
> >  tests/qemucapabilitiesdata/caps_2.6.0.ppc64le.xml  |  3 +
> >  tests/qemucapabilitiesdata/caps_2.6.0.x86_64.xml   |  3 +
> >  tests/qemucapabilitiesdata/caps_2.7.0.s390x.xml    |  3 +
> >  tests/qemucapabilitiesdata/caps_2.7.0.x86_64.xml   |  3 +
> >  tests/qemucapabilitiesdata/caps_2.8.0.s390x.xml    |  3 +
> >  tests/qemucapabilitiesdata/caps_2.8.0.x86_64.xml   |  3 +
> >  tests/qemucapabilitiesdata/caps_2.9.0.ppc64le.xml  |  3 +
> >  tests/qemucapabilitiesdata/caps_2.9.0.s390x.xml    |  3 +
> >  tests/qemucapabilitiesdata/caps_2.9.0.x86_64.xml   |  3 +
> >  .../qemuxml2argv-disk-drive-qcow2-cache.args       | 28 +++++++
> >  .../qemuxml2argv-disk-drive-qcow2-cache.xml        | 43 ++++++++++
> >  tests/qemuxml2argvtest.c                           |  4 +
> >  .../qemuxml2xmlout-disk-drive-qcow2-cache.xml      | 43 ++++++++++
> >  tests/qemuxml2xmltest.c                            |  1 +
> >  26 files changed, 386 insertions(+), 1 deletion(-)
> >  create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-disk-drive-qcow2-cache.args
> >  create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-disk-drive-qcow2-cache.xml
> >  create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-drive-qcow2-cache.xml
> >