[libvirt] [PATCH 3/5] qemu: Extract -mem-path building into its own function

[John Ferlan]

On 10/01/2015 08:10 AM, Martin Kletzander wrote:
> That function is called qemuBuildMemPathStr() and will be used in
> other places in the future.  The change in the test suite is proper due
> to the fact that -mem-prealloc makes only sense with -mem-path (from
> qemu documentation -- html/qemu-doc.html).
> 
> Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
> ---
>  src/qemu/qemu_command.c                            | 120 ++++++++++++---------
>  .../qemuxml2argv-hugepages-pages6.args             |   2 +-
>  2 files changed, 73 insertions(+), 49 deletions(-)
> 

Not quite a straight refactor, but it seems OK - just a couple
nit/comments below.  Your call on how/if there's
> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> index 492313cbcba9..17e5cfd71702 100644
> --- a/src/qemu/qemu_command.c
> +++ b/src/qemu/qemu_command.c
> @@ -7981,6 +7981,71 @@ qemuBuildSmpArgStr(const virDomainDef *def,
>  }
> 
>  static int
> +qemuBuildMemPathStr(virQEMUDriverConfigPtr cfg,
> +                    virDomainDefPtr def,
> +                    virQEMUCapsPtr qemuCaps,
> +                    virCommandPtr cmd)
> +{
> +    const long system_page_size = virGetSystemPageSizeKB();

If cpu cycles are important... could save a few by fetching this after
the No-op if hugepages not requested... or refactor a bit to pass it
around since both qemuBuildNumaArgStr and this fetches the same value.

Not required, but just noted...  There was something long ago in my
history where sysconf() calls were noted as "expensive" - not sure what
triggered that repressed memory.

> +    char *mem_path = NULL;
> +    size_t i = 0;
> +
> +    /*
> +     *  No-op if hugepages were not requested.
> +     */
> +    if (!def->mem.nhugepages)
> +        return 0;
> +
> +    /* There is one special case: if user specified "huge"
> +     * pages of regular system pages size.
> +     * And there is nothing to do in this case.
> +     */
> +    if (def->mem.hugepages[0].size == system_page_size)
> +        return 0;

Just clarifying - in this case you wouldn't need to pass -mem-prealloc
in this case.

> +
> +    if (!cfg->nhugetlbfs) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR,
> +                       "%s", _("hugetlbfs filesystem is not mounted "
> +                               "or disabled by administrator config"));
> +        return -1;
> +    }
> +
> +    if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_MEM_PATH)) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR,
> +                       _("hugepage backing not supported by '%s'"),
> +                       def->emulator);
> +        return -1;
> +    }
> +
> +    if (!def->mem.hugepages[0].size) {
> +        if (!(mem_path = qemuGetDefaultHugepath(cfg->hugetlbfs,
> +                                                cfg->nhugetlbfs)))
> +            return -1;
> +    } else {
> +        for (i = 0; i < cfg->nhugetlbfs; i++) {
> +            if (cfg->hugetlbfs[i].size == def->mem.hugepages[0].size)
> +                break;
> +        }
> +
> +        if (i == cfg->nhugetlbfs) {
> +            virReportError(VIR_ERR_INTERNAL_ERROR,
> +                           _("Unable to find any usable hugetlbfs "
> +                             "mount for %llu KiB"),
> +                           def->mem.hugepages[0].size);
> +            return -1;
> +        }
> +
> +        if (!(mem_path = qemuGetHugepagePath(&cfg->hugetlbfs[i])))
> +            return -1;
> +    }
> +
> +    virCommandAddArgList(cmd, "-mem-prealloc", "-mem-path", mem_path, NULL);
> +    VIR_FREE(mem_path);
> +
> +    return 0;
> +}
> +
> +static int
>  qemuBuildNumaArgStr(virQEMUDriverConfigPtr cfg,
>                      virDomainDefPtr def,
>                      virCommandPtr cmd,
> @@ -9354,54 +9419,13 @@ qemuBuildCommandLine(virConnectPtr conn,
>         virCommandAddArgFormat(cmd, "%llu", virDomainDefGetMemoryInitial(def) / 1024);
>      }
> 
> -    if (def->mem.nhugepages && !virDomainNumaGetNodeCount(def->numa)) {
> -        const long system_page_size = virGetSystemPageSizeKB();
> -        char *mem_path = NULL;
> -
> -        if (def->mem.hugepages[0].size == system_page_size) {
> -            /* There is one special case: if user specified "huge"
> -             * pages of regular system pages size. */
> -        } else {
> -            if (!cfg->nhugetlbfs) {
> -                virReportError(VIR_ERR_INTERNAL_ERROR,
> -                               "%s", _("hugetlbfs filesystem is not mounted "
> -                                       "or disabled by administrator config"));
> -                goto error;
> -            }
> -            if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_MEM_PATH)) {
> -                virReportError(VIR_ERR_INTERNAL_ERROR,
> -                               _("hugepage backing not supported by '%s'"),
> -                               def->emulator);
> -                goto error;
> -            }
> -
> -            if (def->mem.hugepages[0].size) {
> -                for (j = 0; j < cfg->nhugetlbfs; j++) {
> -                    if (cfg->hugetlbfs[j].size == def->mem.hugepages[0].size)
> -                        break;
> -                }
> -
> -                if (j == cfg->nhugetlbfs) {
> -                    virReportError(VIR_ERR_INTERNAL_ERROR,
> -                                   _("Unable to find any usable hugetlbfs mount for %llu KiB"),
> -                                   def->mem.hugepages[0].size);
> -                    goto error;
> -                }
> -
> -                if (!(mem_path = qemuGetHugepagePath(&cfg->hugetlbfs[j])))
> -                    goto error;
> -            } else {
> -                if (!(mem_path = qemuGetDefaultHugepath(cfg->hugetlbfs,
> -                                                        cfg->nhugetlbfs)))
> -                    goto error;
> -            }
> -        }
> -
> -        virCommandAddArg(cmd, "-mem-prealloc");
> -        if (mem_path)
> -            virCommandAddArgList(cmd, "-mem-path", mem_path, NULL);
> -        VIR_FREE(mem_path);
> -    }
> +    /*
> +     * Add '-mem-path' parameter here only if there is no numa node
> +     * specified.

Technically adding both -mem-prealloc and -mem-path ;-)

> +     */
> +    if (!virDomainNumaGetNodeCount(def->numa) &&
> +        qemuBuildMemPathStr(cfg, def, qemuCaps, cmd) < 0)
> +        goto error;
> 
>      if (def->mem.locked && !virQEMUCapsGet(qemuCaps, QEMU_CAPS_MLOCK)) {
>          virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> diff --git a/tests/qemuxml2argvdata/qemuxml2argv-hugepages-pages6.args b/tests/qemuxml2argvdata/qemuxml2argv-hugepages-pages6.args
> index 4eccb86e95ae..a3a4e5732622 100644
> --- a/tests/qemuxml2argvdata/qemuxml2argv-hugepages-pages6.args
> +++ b/tests/qemuxml2argvdata/qemuxml2argv-hugepages-pages6.args
> @@ -1,4 +1,4 @@
>  LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test QEMU_AUDIO_DRV=none \
> -/usr/bin/qemu -S -M pc -m 1024 -mem-prealloc -smp 2 -nographic \
> +/usr/bin/qemu -S -M pc -m 1024 -smp 2 -nographic \
>  -monitor unix:/tmp/test-monitor,server,nowait -no-acpi -boot c -usb \
>  -hda /dev/HostVG/QEMUGuest1 -net none -serial none -parallel none
>