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[libvirt] [PATCH v2 5/8] libxl: implement virDomainBlockStats



Introduce initial support for domainBlockStats API call that
allow us to query block device statistics. openstack nova
uses this API call to query block statistics, alongside
virDomainMemoryStats and virDomainInterfaceStats.  Note that
this patch only introduces it for VBD for starters. QDisk
will come in a separate patch series.

A new statistics data structure is introduced to fit common
statistics among others specific to the underlying block
backends. For the VBD statistics on linux these are exported
via sysfs on the path:

"/sys/bus/xen-backend/devices/vbd-<domid>-<devid>/statistics"

To calculate the block devno libxlDiskPathToID is introduced.
Each backend implements its own function to extract statistics
and let there be handled the different platforms. An alternative
would be to reuse libvirt xen driver function.

VBD stats are exposed in reqs and number of sectors from
blkback, and it's up to us to convert it to sector sizes.
The sector size is gathered through xenstore in the device
backend entry "physical-sector-size". This adds up an extra
dependency namely of xenstore for doing the xs_read.

BlockStatsFlags variant is also implemented which has the
added benefit of getting the number of flush requests.

Signed-off-by: Joao Martins <joao m martins oracle com>
---
Changes since v1:
 - Fix identation issues
 - Set ret to LIBXL_VBD_SECTOR_SIZE
 - Reuse VIR_STRDUP error instead of doing virReportError
 when we fail to set stats->backend
 - Change virAsprintf(...) error checking
 - Change error to VIR_ERR_OPERATION_FAILED when xenstore path
 does not exist and when failing to read stat.
 - Resolve issues with 'make syntax-check' with cppi installed.
 - Remove libxlDiskPathMatches in favor of using virutil
 virDiskNameParse to fetch disk and partition index.
 - Rename libxlDiskPathParse to libxlDiskPathToID and rework
 function to just convert disk and partition index to devno.
 - Bump version to 1.2.22
---
 configure.ac             |   2 +-
 src/libxl/libxl_driver.c | 375 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 376 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index f481c50..10c56e5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -896,7 +896,7 @@ if test "$with_libxl" != "no" ; then
         LIBS="$LIBS $LIBXL_LIBS"
         AC_CHECK_LIB([xenlight], [libxl_ctx_alloc], [
             with_libxl=yes
-            LIBXL_LIBS="$LIBXL_LIBS -lxenlight -lxenctrl"
+            LIBXL_LIBS="$LIBXL_LIBS -lxenlight -lxenctrl -lxenstore"
         ],[
             if test "$with_libxl" = "yes"; then
                 fail=1
diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c
index 9a5a74c..ba1d67b 100644
--- a/src/libxl/libxl_driver.c
+++ b/src/libxl/libxl_driver.c
@@ -59,6 +59,7 @@
 #include "network/bridge_driver.h"
 #include "locking/domain_lock.h"
 #include "virstats.h"
+#include <xenstore.h>
 
 #define VIR_FROM_THIS VIR_FROM_LIBXL
 
@@ -75,6 +76,7 @@ VIR_LOG_INIT("libxl.libxl_driver");
 #define LIBXL_CONFIG_FORMAT_SEXPR "xen-sxpr"
 
 #define LIBXL_NB_TOTAL_CPU_STAT_PARAM 1
+#define LIBXL_NB_TOTAL_BLK_STAT_PARAM 6
 
 #define HYPERVISOR_CAPABILITIES "/proc/xen/capabilities"
 #define HYPERVISOR_XENSTORED "/dev/xen/xenstored"
@@ -103,6 +105,25 @@ struct _libxlOSEventHookInfo {
     int id;
 };
 
+/* Object used to store disk statistics across multiple xen backends */
+typedef struct _libxlBlockStats libxlBlockStats;
+typedef libxlBlockStats *libxlBlockStatsPtr;
+struct _libxlBlockStats {
+    long long rd_req;
+    long long rd_bytes;
+    long long wr_req;
+    long long wr_bytes;
+    long long f_req;
+
+    char *backend;
+    union {
+        struct {
+            long long ds_req;
+            long long oo_req;
+        } vbd;
+    } u;
+};
+
 /* Function declarations */
 static int
 libxlDomainManagedSaveLoad(virDomainObjPtr vm,
@@ -4644,6 +4665,358 @@ libxlDomainIsUpdated(virDomainPtr dom)
 }
 
 static int
+libxlDiskPathToID(const char *virtpath)
+{
+    static char const* drive_prefix[] = {"xvd", "hd", "sd"};
+    int disk, partition, chrused;
+    int fmt, id;
+    char *r;
+    size_t i;
+
+    fmt = id = -1;
+
+    /* Find any disk prefixes we know about */
+    for (i = 0; i < ARRAY_CARDINALITY(drive_prefix); i++) {
+        if (STRPREFIX(virtpath, drive_prefix[i]) &&
+            !virDiskNameParse(virtpath, &disk, &partition)) {
+            fmt = i;
+            break;
+        }
+    }
+
+    /* Handle it same way as xvd */
+    if (fmt < 0 &&
+        (sscanf(virtpath, "d%ip%i%n", &disk, &partition, &chrused) >= 2
+         && chrused == strlen(virtpath)))
+        fmt = 0;
+
+    /* Test indexes ranges and calculate the device id */
+    switch (fmt) {
+    case 0: /* xvd */
+        if (disk <= 15 && partition <= 15)
+            id = (202 << 8) | (disk << 4) | partition;
+        else if ((disk <= ((1<<20)-1)) || partition <= 255)
+            id = (1 << 28) | (disk << 8) | partition;
+        break;
+    case 1: /* hd */
+        if (disk <= 3 && partition <= 63)
+            id = ((disk < 2 ? 3 : 22) << 8) | ((disk & 1) << 6) | partition;
+        break;
+    case 2: /* sd */
+        if (disk <= 15 && (partition <= 15))
+            id = (8 << 8) | (disk << 4) | partition;
+        break;
+    default:
+        errno = virStrToLong_i(virtpath, &r, 0, &id);
+        if (errno || *r || id > INT_MAX)
+            id = -1;
+        break;
+    }
+    return id;
+}
+
+#define LIBXL_VBD_SECTOR_SIZE 512
+
+static int
+libxlDiskSectorSize(int domid, int devno)
+{
+    char *path, *val;
+    struct xs_handle *handle;
+    int ret = LIBXL_VBD_SECTOR_SIZE;
+    unsigned int len;
+
+    handle = xs_daemon_open_readonly();
+    if (!handle) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       "%s", _("cannot read sector size"));
+        return ret;
+    }
+
+    if (virAsprintf(&path, "/local/domain/%d/device/vbd/%d/backend",
+                    domid, devno) < 0)
+        goto close;
+
+    if ((val = xs_read(handle, XBT_NULL, path, &len)) == NULL)
+        goto cleanup;
+
+    VIR_FREE(path);
+    if (virAsprintf(&path, "%s/physical-sector-size", val) < 0) {
+        VIR_FREE(val);
+        goto close;
+    }
+
+    VIR_FREE(val);
+    if ((val = xs_read(handle, XBT_NULL, path, &len)) == NULL)
+        goto cleanup;
+
+    if (sscanf(val, "%d", &ret) != 1)
+        ret = LIBXL_VBD_SECTOR_SIZE;
+
+    VIR_FREE(val);
+
+ cleanup:
+    VIR_FREE(path);
+ close:
+    xs_daemon_close(handle);
+    return ret;
+}
+
+static int
+libxlDomainBlockStatsVBD(virDomainObjPtr vm,
+                         const char *dev,
+                         libxlBlockStatsPtr stats)
+{
+    int ret = -1;
+    int devno = libxlDiskPathToID(dev);
+    int size = libxlDiskSectorSize(vm->def->id, devno);
+#ifdef __linux__
+    char *path, *name, *val;
+    unsigned long long stat;
+
+    path = name = val = NULL;
+    if (devno < 0) {
+        virReportError(VIR_ERR_OPERATION_INVALID,
+                       "%s", _("cannot find device number"));
+        return ret;
+    }
+    if (VIR_STRDUP(stats->backend, "vbd") < 0)
+        return ret;
+
+    if (virAsprintf(&path, "/sys/bus/xen-backend/devices/vbd-%d-%d/statistics",
+                    vm->def->id, devno) < 0)
+        return ret;
+
+    if (!virFileExists(path)) {
+        virReportError(VIR_ERR_OPERATION_FAILED,
+                       "%s", _("cannot open bus path"));
+        goto cleanup;
+    }
+
+# define LIBXL_SET_VBDSTAT(FIELD, VAR, MUL)           \
+    if ((virAsprintf(&name, "%s/"FIELD, path) < 0) || \
+        (virFileReadAll(name, 256, &val) < 0) ||      \
+        (sscanf(val, "%llu", &stat) != 1)) {          \
+        virReportError(VIR_ERR_OPERATION_FAILED,     \
+                       _("cannot read %s"), name);    \
+        goto cleanup;                                 \
+    }                                                 \
+    VAR += (stat * MUL);                              \
+    VIR_FREE(name);                                   \
+    VIR_FREE(val);
+
+    LIBXL_SET_VBDSTAT("f_req",  stats->f_req,  1)
+    LIBXL_SET_VBDSTAT("wr_req", stats->wr_req, 1)
+    LIBXL_SET_VBDSTAT("rd_req", stats->rd_req, 1)
+    LIBXL_SET_VBDSTAT("wr_sect", stats->wr_bytes, size)
+    LIBXL_SET_VBDSTAT("rd_sect", stats->rd_bytes, size)
+
+    LIBXL_SET_VBDSTAT("ds_req", stats->u.vbd.ds_req, size)
+    LIBXL_SET_VBDSTAT("oo_req", stats->u.vbd.oo_req, 1)
+    ret = 0;
+
+ cleanup:
+    VIR_FREE(name);
+    VIR_FREE(path);
+    VIR_FREE(val);
+
+# undef LIBXL_SET_VBDSTAT
+
+#else
+    virReportError(VIR_ERR_OPERATION_UNSUPPORTED,
+                   "%s", _("platform unsupported"));
+#endif
+    return ret;
+}
+
+static int
+libxlDomainBlockStatsGatherSingle(virDomainObjPtr vm,
+                                  const char *path,
+                                  libxlBlockStatsPtr stats)
+{
+    virDomainDiskDefPtr disk;
+    const char *disk_drv;
+    int ret = -1, disk_fmt;
+
+    if (!(disk = virDomainDiskByName(vm->def, path, false))) {
+        virReportError(VIR_ERR_OPERATION_INVALID,
+                       _("invalid path: %s"), path);
+        return ret;
+    }
+
+    disk_fmt = virDomainDiskGetFormat(disk);
+    if (!(disk_drv = virDomainDiskGetDriver(disk)))
+        disk_drv = "qemu";
+
+    if (STREQ(disk_drv, "phy")) {
+        if (disk_fmt != VIR_STORAGE_FILE_RAW &&
+            disk_fmt != VIR_STORAGE_FILE_NONE) {
+            virReportError(VIR_ERR_OPERATION_UNSUPPORTED,
+                           _("unsupported format %s"),
+                           virStorageFileFormatTypeToString(disk_fmt));
+            return ret;
+        }
+
+        ret = libxlDomainBlockStatsVBD(vm, path, stats);
+    } else {
+            virReportError(VIR_ERR_OPERATION_UNSUPPORTED,
+                           _("unsupported disk driver %s"),
+                           disk_drv);
+            return ret;
+    }
+    return ret;
+}
+
+static int
+libxlDomainBlockStatsGather(virDomainObjPtr vm,
+                            const char *path,
+                            libxlBlockStatsPtr stats)
+{
+    int ret = -1;
+    if (*path) {
+        if (libxlDomainBlockStatsGatherSingle(vm, path, stats) < 0)
+            return ret;
+    } else {
+        size_t i;
+        for (i = 0; i < vm->def->ndisks; ++i) {
+            if (libxlDomainBlockStatsGatherSingle(vm, vm->def->disks[i]->dst,
+                                                  stats) < 0)
+                return ret;
+        }
+    }
+    return 0;
+}
+
+static int
+libxlDomainBlockStats(virDomainPtr dom,
+                      const char *path,
+                      virDomainBlockStatsPtr stats)
+{
+    libxlDriverPrivatePtr driver = dom->conn->privateData;
+    virDomainObjPtr vm;
+    libxlBlockStats blkstats;
+    int ret = -1;
+
+    if (!(vm = libxlDomObjFromDomain(dom)))
+        goto cleanup;
+
+    if (virDomainBlockStatsEnsureACL(dom->conn, vm->def) < 0)
+        goto cleanup;
+
+    if (libxlDomainObjBeginJob(driver, vm, LIBXL_JOB_QUERY) < 0)
+        goto cleanup;
+
+    if (!virDomainObjIsActive(vm)) {
+        virReportError(VIR_ERR_OPERATION_INVALID,
+                       "%s", _("domain is not running"));
+        goto endjob;
+    }
+
+    memset(&blkstats, 0, sizeof(libxlBlockStats));
+    if ((ret = libxlDomainBlockStatsGather(vm, path, &blkstats)) < 0)
+        goto endjob;
+
+    stats->rd_req = blkstats.rd_req;
+    stats->rd_bytes = blkstats.rd_bytes;
+    stats->wr_req = blkstats.wr_req;
+    stats->wr_bytes = blkstats.wr_bytes;
+    if (STREQ_NULLABLE(blkstats.backend, "vbd"))
+        stats->errs = blkstats.u.vbd.oo_req;
+    else
+        stats->errs = -1;
+
+ endjob:
+    if (!libxlDomainObjEndJob(driver, vm)) {
+        virObjectUnlock(vm);
+        vm = NULL;
+    }
+
+ cleanup:
+    if (vm)
+        virObjectUnlock(vm);
+    return ret;
+}
+
+static int
+libxlDomainBlockStatsFlags(virDomainPtr dom,
+                           const char *path,
+                           virTypedParameterPtr params,
+                           int *nparams,
+                           unsigned int flags)
+{
+    libxlDriverPrivatePtr driver = dom->conn->privateData;
+    virDomainObjPtr vm;
+    libxlBlockStats blkstats;
+    int nstats;
+    int ret = -1;
+
+    virCheckFlags(VIR_TYPED_PARAM_STRING_OKAY, -1);
+
+    flags &= ~VIR_TYPED_PARAM_STRING_OKAY;
+
+    if (!(vm = libxlDomObjFromDomain(dom)))
+        goto cleanup;
+
+    if (virDomainBlockStatsFlagsEnsureACL(dom->conn, vm->def) < 0)
+        goto cleanup;
+
+    if (libxlDomainObjBeginJob(driver, vm, LIBXL_JOB_QUERY) < 0)
+        goto cleanup;
+
+    if (!virDomainObjIsActive(vm)) {
+        virReportError(VIR_ERR_OPERATION_INVALID,
+                       "%s", _("domain is not running"));
+        goto endjob;
+    }
+
+    /* return count of supported stats */
+    if (*nparams == 0) {
+        *nparams = LIBXL_NB_TOTAL_BLK_STAT_PARAM;
+        ret = 0;
+        goto endjob;
+    }
+
+    memset(&blkstats, 0, sizeof(libxlBlockStats));
+    if ((ret = libxlDomainBlockStatsGather(vm, path, &blkstats)) < 0)
+        goto endjob;
+
+    nstats = 0;
+
+#define LIBXL_BLKSTAT_ASSIGN_PARAM(VAR, NAME)                              \
+    if (nstats < *nparams && (blkstats.VAR) != -1) {                       \
+        if (virTypedParameterAssign(params + nstats, NAME,                 \
+                                    VIR_TYPED_PARAM_LLONG, (blkstats.VAR)) < 0) \
+            goto endjob;                                                   \
+        nstats++;                                                          \
+    }
+
+    LIBXL_BLKSTAT_ASSIGN_PARAM(wr_bytes, VIR_DOMAIN_BLOCK_STATS_WRITE_BYTES);
+    LIBXL_BLKSTAT_ASSIGN_PARAM(wr_req, VIR_DOMAIN_BLOCK_STATS_WRITE_REQ);
+
+    LIBXL_BLKSTAT_ASSIGN_PARAM(rd_bytes, VIR_DOMAIN_BLOCK_STATS_READ_BYTES);
+    LIBXL_BLKSTAT_ASSIGN_PARAM(rd_req, VIR_DOMAIN_BLOCK_STATS_READ_REQ);
+
+    LIBXL_BLKSTAT_ASSIGN_PARAM(f_req, VIR_DOMAIN_BLOCK_STATS_FLUSH_REQ);
+
+    if (STREQ_NULLABLE(blkstats.backend, "vbd"))
+        LIBXL_BLKSTAT_ASSIGN_PARAM(u.vbd.oo_req, VIR_DOMAIN_BLOCK_STATS_ERRS);
+
+    *nparams = nstats;
+
+#undef LIBXL_BLKSTAT_ASSIGN_PARAM
+
+ endjob:
+    if (!libxlDomainObjEndJob(driver, vm)) {
+        virObjectUnlock(vm);
+        vm = NULL;
+    }
+
+ cleanup:
+    if (vm)
+        virObjectUnlock(vm);
+    return ret;
+}
+
+static int
 libxlDomainInterfaceStats(virDomainPtr dom,
                           const char *path,
                           virDomainInterfaceStatsPtr stats)
@@ -5458,6 +5831,8 @@ static virHypervisorDriver libxlHypervisorDriver = {
 #endif
     .nodeGetFreeMemory = libxlNodeGetFreeMemory, /* 0.9.0 */
     .nodeGetCellsFreeMemory = libxlNodeGetCellsFreeMemory, /* 1.1.1 */
+    .domainBlockStats = libxlDomainBlockStats, /* 1.2.22 */
+    .domainBlockStatsFlags = libxlDomainBlockStatsFlags, /* 1.2.22 */
     .domainInterfaceStats = libxlDomainInterfaceStats, /* 1.2.22 */
     .domainMemoryStats = libxlDomainMemoryStats, /* 1.2.22 */
     .domainGetCPUStats = libxlDomainGetCPUStats, /* 1.2.22 */
-- 
2.1.4


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