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Re: [libvirt] [PATCHv4 4/4] blkiotune: add qemu support for blkiotune.device_weight



On Mon, Nov 14, 2011 at 09:30:02PM -0700, Eric Blake wrote:
> From: Hu Tao <hutao cn fujitsu com>
> 
> Implement setting/getting per-device blkio weights in qemu,
> using the cgroups blkio.weight_device tunable.
> ---
>  src/libvirt_private.syms                           |    1 +
>  src/qemu/qemu_cgroup.c                             |   20 ++
>  src/qemu/qemu_driver.c                             |  218 +++++++++++++++++++-
>  src/util/cgroup.c                                  |   51 +++++
>  src/util/cgroup.h                                  |    4 +
>  .../qemuxml2argv-blkiotune-device.args             |    4 +
>  tests/qemuxml2argvtest.c                           |    1 +
>  tests/qemuxml2xmltest.c                            |    1 +
>  8 files changed, 295 insertions(+), 5 deletions(-)
>  create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-blkiotune-device.args
> 
> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> index d78fd53..3575fe0 100644
> --- a/src/libvirt_private.syms
> +++ b/src/libvirt_private.syms
> @@ -89,6 +89,7 @@ virCgroupKillRecursive;
>  virCgroupMounted;
>  virCgroupPathOfController;
>  virCgroupRemove;
> +virCgroupSetBlkioDeviceWeight;
>  virCgroupSetBlkioWeight;
>  virCgroupSetCpuShares;
>  virCgroupSetCpuCfsPeriod;
> diff --git a/src/qemu/qemu_cgroup.c b/src/qemu/qemu_cgroup.c
> index 2a10bd2..eda4c66 100644
> --- a/src/qemu/qemu_cgroup.c
> +++ b/src/qemu/qemu_cgroup.c
> @@ -312,6 +312,26 @@ int qemuSetupCgroup(struct qemud_driver *driver,
>          }
>      }
> 
> +    if (vm->def->blkio.ndevices) {
> +        if (qemuCgroupControllerActive(driver, VIR_CGROUP_CONTROLLER_BLKIO)) {
> +            for (i = 0; i < vm->def->blkio.ndevices; i++) {
> +                virBlkioDeviceWeightPtr dw = &vm->def->blkio.devices[i];
> +                rc = virCgroupSetBlkioDeviceWeight(cgroup, dw->path,
> +                                                   dw->weight);
> +                if (rc != 0) {
> +                    virReportSystemError(-rc,
> +                                         _("Unable to set io device weight "
> +                                           "for domain %s"),
> +                                         vm->def->name);
> +                    goto cleanup;
> +                }
> +            }
> +        } else {
> +            qemuReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                            _("Block I/O tuning is not available on this host"));
> +        }
> +    }
> +
>      if (vm->def->mem.hard_limit != 0 ||
>          vm->def->mem.soft_limit != 0 ||
>          vm->def->mem.swap_hard_limit != 0) {
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index b0ce115..43f4041 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -112,7 +112,7 @@
>  # define KVM_CAP_NR_VCPUS 9       /* returns max vcpus per vm */
>  #endif
> 
> -#define QEMU_NB_BLKIO_PARAM  1
> +#define QEMU_NB_BLKIO_PARAM  2
> 
>  static void processWatchdogEvent(void *data, void *opaque);
> 
> @@ -5885,6 +5885,105 @@ cleanup:
>      return ret;
>  }
> 
> +/* deviceWeightStr in the form of /device/path,weight,/device/path,weight
> + * for example, /dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0,800
> + */
> +static int
> +parseBlkioWeightDeviceStr(char *deviceWeightStr,
> +                          virBlkioDeviceWeightPtr *dw, int *size,
> +                          virCgroupPtr cgroup)
> +{
> +    char *temp;
> +    int ndevices = 0;
> +    int nsep = 0;
> +    int i;
> +    virBlkioDeviceWeightPtr result = NULL;
> +
> +    temp = deviceWeightStr;
> +    while (temp) {
> +        temp = strchr(temp, ',');
> +        if (temp) {
> +            temp++;
> +            nsep++;
> +        }
> +    }
> +
> +    /* A valid string must have even number of fields, hence an odd
> +     * number of commas.  */
> +    if (!(nsep & 1))
> +        goto error;
> +
> +    ndevices = (nsep + 1) / 2;
> +
> +    if (VIR_ALLOC_N(result, ndevices) < 0) {
> +        virReportOOMError();
> +        return -1;
> +    }
> +
> +    i = 0;
> +    temp = deviceWeightStr;
> +    while (temp) {
> +        char *p = temp;
> +
> +        /* device path */
> +        p = strchr(p, ',');
> +        if (!p)
> +            goto error;
> +
> +        result[i].path = strndup(temp, p - temp);
> +        if (!result[i].path) {
> +            virReportOOMError();
> +            goto cleanup;
> +        }
> +
> +        /* weight */
> +        temp = p + 1;
> +
> +        if (virStrToLong_ui(temp, &p, 10, &result[i].weight) < 0)
> +            goto error;
> +
> +        if (cgroup) {
> +            int rc = virCgroupSetBlkioDeviceWeight(cgroup,
> +                                                   result[i].path,
> +                                                   result[i].weight);

Does more than the function name says. Would it be better to just do the
parsing here, and set the cgroup values after parsing(see my comment to
patch 3 for filtering out 0-weight when writing to xml):

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 43f4041..275d5c8 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -5890,8 +5890,7 @@ cleanup:
  */
 static int
 parseBlkioWeightDeviceStr(char *deviceWeightStr,
-                          virBlkioDeviceWeightPtr *dw, int *size,
-                          virCgroupPtr cgroup)
+                          virBlkioDeviceWeightPtr *dw, int *size)
 {
     char *temp;
     int ndevices = 0;
@@ -5942,24 +5941,8 @@ parseBlkioWeightDeviceStr(char *deviceWeightStr,
         if (virStrToLong_ui(temp, &p, 10, &result[i].weight) < 0)
             goto error;
 
-        if (cgroup) {
-            int rc = virCgroupSetBlkioDeviceWeight(cgroup,
-                                                   result[i].path,
-                                                   result[i].weight);
-            if (rc < 0) {
-                virReportSystemError(-rc,
-                                     _("Unable to set io device weight "
-                                       "for path %s"),
-                                     result[i].path);
-                goto cleanup;
-            }
-        }
+        i++;
 
-        /* 0-weight entries only affect cgroups, they don't stick in xml */
-        if (result[i].weight)
-            i++;
-        else
-            VIR_FREE(result[i].path);
         if (*p == '\0')
             break;
         else if (*p != ',')
@@ -6087,7 +6070,23 @@ static int qemuDomainSetBlkioParameters(virDomainPtr dom,
 
                 if (parseBlkioWeightDeviceStr(params[i].value.s,
                                               &devices,
-                                              &ndevices, group) < 0) {
+                                              &ndevices) < 0) {
+                    ret = -1;
+                    continue;
+                }
+                for (i = 0; i < ndevices; i++) {
+                    rc = virCgroupSetBlkioDeviceWeight(group,
+                                                       devices[i].path,
+                                                       devices[i].weight);
+                    if (rc < 0) {
+                        virReportSystemError(-rc,
+                                             _("Unable to set io device weight "
+                                               "for path %s"),
+                                             devices[i].path);
+                        break;
+                    }
+                }
+                if (i != ndevices) {
                     ret = -1;
                     continue;
                 }
@@ -6140,7 +6139,7 @@ static int qemuDomainSetBlkioParameters(virDomainPtr dom,
                 }
                 if (parseBlkioWeightDeviceStr(params[i].value.s,
                                               &devices,
-                                              &ndevices, NULL) < 0) {
+                                              &ndevices) < 0) {
                     ret = -1;
                     continue;
                 }


-- 
Thanks,
Hu Tao


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