Re: [libvirt] [PATCH v2 0/2] Add support for zero-write detection
On 12/14/2015 09:57 AM, Martin Kletzander wrote:
QEMU supports detect-zeroes option since version 2.1, but we never
added support for it in libvirt. If was requested by Vasiliy Tolstov
in the list, so I just added it.
There are two discussions to be had, optionally. One is to decide
whether we should disable detect_zeros='unmap' if discard is not set
to 'unmap', but this is getting very hypervisor-specific, so I just
documented the behaviour. The other one is the naming. I described
why I made the decision for "zeros" instead of "zeroes" the decision
in the patch, but I have no problem changing it to what others like
better.
Unfortunate that qemu chose "zeroes" instead of "zeros" or instead of
"detect_zero_writes" (or something even longer and more descriptive).
Seems strange though to say "detect_zeros=unmap". Would perhaps
something like :
detect = zero_write [or just zero, zeros, or zeroes]
detect = unmap
...
or
detect_zero = write
detect_zero = unmap
...
Be more generic? Also, I would think detect_zero[e]s = off is
meaningless since it's an optional parameter. The way the code is
written, passing detect_zeroes=off to me would be akin to not providing
it at all.
I think from my quick read - this would be similar to the "discard"
option, w.r.t. values used/set.
John
v2:
- format detect_zeroes on the command line instead of detect_zeros
v1:
- https://www.redhat.com/archives/libvir-list/2015-December/msg00484.html
Martin Kletzander (2):
conf: Add support of zero-detection for disks
qemu: Add support for zero-detection writes
docs/formatdomain.html.in | 10 ++++++
docs/schemas/domaincommon.rng | 12 +++++++
src/conf/domain_conf.c | 23 +++++++++++++-
src/conf/domain_conf.h | 11 +++++++
src/libvirt_private.syms | 2 ++
src/qemu/qemu_capabilities.c | 2 ++
src/qemu/qemu_capabilities.h | 1 +
src/qemu/qemu_command.c | 11 +++++++
tests/qemucapabilitiesdata/caps_2.1.1-1.caps | 1 +
tests/qemucapabilitiesdata/caps_2.4.0-1.caps | 1 +
tests/qemucapabilitiesdata/caps_2.5.0-1.caps | 1 +
.../qemuxml2argv-disk-drive-detect-zeros.args | 27 ++++++++++++++++
.../qemuxml2argv-disk-drive-detect-zeros.xml | 37 ++++++++++++++++++++++
tests/qemuxml2argvtest.c | 4 +++
tests/qemuxml2xmltest.c | 1 +
15 files changed, 143 insertions(+), 1 deletion(-)
create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-disk-drive-detect-zeros.args
create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-disk-drive-detect-zeros.xml
--
2.6.4
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