6:01 a.m.
On Thu, Oct 01, 2015 at 07:50:09PM -0400, John Ferlan wrote:
On 10/01/2015 08:10 AM, Martin Kletzander wrote:
> We are using memory-backing-file even when it's not needed, for example
> if user requests hugepages for mamory backing, but does not specify any
^^^^^^
Different body part altogether ;-)
> pagesize, neither memory node pinning. This causes migrations to fail
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Doesn't read well - as in I'm not quite sure what you meant... Neither
and nor are usually paired together if that helps any
I edited that few times and messed that up during those edits
probably. I did s/, neither/ or/ so it reads more cleanly.
> when migrating from older libvirt that did not do this. So
similarly to
> commit 7832fac84741d65e851dbdbfaf474785cbfdcf3c which does it for
> memory-backend-ram, this commit makes is more generic and
> backend-agnostic, so the backend is not used if there is no specific
> pagesize of hugepages requested, no nodeset the memory node should be
> bound to, no memory access change required, and so on.
>
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1266856
>
> Signed-off-by: Martin Kletzander <mkletzan(a)redhat.com>
> ---
> src/qemu/qemu_command.c | 36 ++++++++++------------
> .../qemuxml2argv-hugepages-numa.args | 6 ++--
> 2 files changed, 19 insertions(+), 23 deletions(-)
>
> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> index 321a5e931350..7ff3e535a543 100644
> --- a/src/qemu/qemu_command.c
> +++ b/src/qemu/qemu_command.c
> @@ -5120,12 +5120,6 @@ qemuBuildMemoryBackendStr(unsigned long long size,
> }
>
> if (pagesize || hugepage) {
> - if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_MEMORY_FILE)) {
> - virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> - _("this qemu doesn't support hugepage memory
backing"));
> - goto cleanup;
> - }
> -
Wasn't clear to me why this was removed. The code that follows within
the if will create a memory-backend-file
This code is a hairy ball of **** ***. This function creates the
objects, but only after all of them are created we know whether the
backend is needed or not (you cannot mix mem= and memdev= in -numa
specification). So only after all that is done, the objects are
either transformed into '-num' parameter or not.
So with the change that I'm doing here it just removes the check
simply because we don't know yet whether memory-backend-file object
will be needed or not, and the decision is moved downwards.
I see below the check is made in the else case but there's no
hugepage
the list of !x && !y && !z ...
That's exactly aligned with the change I'm doing here. You don't need
memory-backend-file just because hugepage backing is requested.
Perhaps I'm being thrown by the use of "pagesize" and
"hugepage"
conditions. The 'hugepage' only gets set if 'pagesize = 0'... If
'hugepage' is set, can pagesize be '0' (outside if pagesize ==
system_page_size)
Sorry - just trying to think through the logic...
No problem, that's the important part to understand what I'm doing
here. And I understand this change is definitely not
straight-forward, that's why I was trying to make the last commit as
small and self-contained as possible.
I guess removing it is fine, but it's not obvious without digging
in a
bit...
> if (pagesize) {
> /* Now lets see, if the huge page we want to use is even mounted
> * and ready to use */
> @@ -5204,29 +5198,31 @@ qemuBuildMemoryBackendStr(unsigned long long size,
> goto cleanup;
> }
>
> - if (!hugepage && !pagesize) {
> -
> - if ((userNodeset || nodeSpecified || force) &&
> - !virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_MEMORY_RAM)) {
> + /* If none of the following is requested... */
> + if (!pagesize && !userNodeset && !memAccess &&
!nodeSpecified && !force) {
hmmm. force isn't documented - in the input args... I know different problem
Force means that we must use the memory-backend-{file-ram}. With
force == true, this function is called to construct the object for
memory device as opposed to numa node memory.
> + /* report back that using the new backend is not
necessary
> + * to achieve the desired configuration */
> + ret = 1;
> + } else {
> + /* otherwise check the required capability */
> + if (STREQ(*backendType, "memory-backend-file") &&
> + !virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_MEMORY_FILE)) {
> virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> _("this qemu doesn't support the "
> - "memory-backend-ram object"));
> + "memory-backend-file object"));
> goto cleanup;
> + } else if (STREQ(*backendType, "memory-backend-ram") &&
> + !virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_MEMORY_RAM)) {
> + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> + _("this qemu doesn't support the "
> + "memory-backend-ram object"));
> }
>
> - /* report back that using the new backend is not necessary to achieve
> - * the desired configuration */
> - if (!userNodeset && !nodeSpecified) {
> - *backendProps = props;
> - props = NULL;
> - ret = 1;
> - goto cleanup;
> - }
> + ret = 0;
As confusing as the diff is - it looks cleaner in it's final version.
yes, I didn't know how to split any more of this out into separate
commits, sorry.
Hopefully Michal or Peter can also look at the final product - it
looks
good to me though
ACK with some adjustments
I'll se if they have anything to say, thanks for the review!
John
> }
>
> *backendProps = props;
> props = NULL;
> - ret = 0;
>
> cleanup:
> virJSONValueFree(props);
> diff --git a/tests/qemuxml2argvdata/qemuxml2argv-hugepages-numa.args
b/tests/qemuxml2argvdata/qemuxml2argv-hugepages-numa.args
> index 37511b109b6e..3496cf1a732d 100644
> --- a/tests/qemuxml2argvdata/qemuxml2argv-hugepages-numa.args
> +++ b/tests/qemuxml2argvdata/qemuxml2argv-hugepages-numa.args
> @@ -4,9 +4,9 @@ LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test
QEMU_AUDIO_DRV=spice \
> -M pc-i440fx-2.3 \
> -m size=1048576k,slots=16,maxmem=1099511627776k \
> -smp 2 \
> --object memory-backend-file,id=ram-node0,prealloc=yes,\
> -mem-path=/dev/hugepages2M/libvirt/qemu,size=1073741824 \
> --numa node,nodeid=0,cpus=0-1,memdev=ram-node0 \
> +-mem-prealloc \
> +-mem-path /dev/hugepages2M/libvirt/qemu \
> +-numa node,nodeid=0,cpus=0-1,mem=1024 \
> -object memory-backend-file,id=memdimm0,prealloc=yes,\
> mem-path=/dev/hugepages1G/libvirt/qemu,size=1073741824,host-nodes=1-3,policy=bind \
> -device pc-dimm,node=0,memdev=memdimm0,id=dimm0 \
>