Re: [PATCH v4] libxl: implement virDomainBlockStats

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On 07/20/2016 04:48 PM, Joao Martins wrote:
> 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
> would 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.

Too bad libxl or libxlutil doesn't provide such a function.

> Each backend implements its own function to extract statistics
> and let there be handled the different platforms.
>
> 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".
>
> 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@xxxxxxxxxx>
> ---
> Changes since v3:
>  - No need for error in libxlDiskSectorSize()
>  - Fix an identation issue.
>  - Rework cleanup paths on libxlDiskSectorSize()
>  - Do not unlock vm if libxlDomainObjEndJob() returns false and
>  adjust to the newly introduced virDomainObjEndAPI()
>  - Bump version to 2.1.0
>
> 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
> ---
>  src/libxl/libxl_driver.c | 364 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 364 insertions(+)
>
> diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c
> index f153f69..189bfb5 100644
> --- a/src/libxl/libxl_driver.c
> +++ b/src/libxl/libxl_driver.c
> @@ -30,6 +30,7 @@
>  #include <math.h>
>  #include <libxl.h>
>  #include <libxl_utils.h>
> +#include <xenstore.h>
>  #include <fcntl.h>
>  #include <regex.h>
>  
> @@ -72,6 +73,7 @@ VIR_LOG_INIT("libxl.libxl_driver");
>  #define LIBXL_DOM_REQ_HALT     4
>  
>  #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"
> @@ -100,6 +102,25 @@ 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,
> @@ -5031,6 +5052,347 @@ libxlDomainGetJobStats(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;

The purpose of the default case is not clear to me. Can you explain that a bit? 
IIUC, virtpath would contain values such as xvda, sdc, or /path/to/image.

> +    }
> +    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) {
> +        VIR_WARN("cannot read sector size");
> +        return ret;
> +    }
> +
> +    path = val = NULL;
> +    if (virAsprintf(&path, "/local/domain/%d/device/vbd/%d/backend",
> +                    domid, devno) < 0)
> +        goto cleanup;
> +
> +    if ((val = xs_read(handle, XBT_NULL, path, &len)) == NULL)
> +        goto cleanup;
> +
> +    VIR_FREE(path);
> +    if (virAsprintf(&path, "%s/physical-sector-size", val) < 0)
> +        goto cleanup;
> +
> +    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;
> +
> + cleanup:
> +    VIR_FREE(val);
> +    VIR_FREE(path);
> +    xs_daemon_close(handle);
> +    return ret;
> +}
> +
> +static int
> +libxlDomainBlockStatsVBD(virDomainObjPtr vm,
> +                         const char *dev,
> +                         libxlBlockStatsPtr stats)

The stats parameter is unused when __linux__ is not defined. Otherwise, the
patch looks fine.

Regards,
Jim


> +{
> +    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;
> +}
> +
> +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:
> +    libxlDomainObjEndJob(driver, vm);
> +
> + cleanup:
> +    virDomainObjEndAPI(&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:
> +    libxlDomainObjEndJob(driver, vm);
> +
> + cleanup:
> +    virDomainObjEndAPI(&vm);
> +    return ret;
> +}
> +
> +static int
>  libxlConnectDomainEventRegisterAny(virConnectPtr conn, virDomainPtr dom, int eventID,
>                                     virConnectDomainEventGenericCallback callback,
>                                     void *opaque, virFreeCallback freecb)
> @@ -5847,6 +6209,8 @@ static virHypervisorDriver libxlHypervisorDriver = {
>      .domainMemoryStats = libxlDomainMemoryStats, /* 1.3.0 */
>      .domainGetCPUStats = libxlDomainGetCPUStats, /* 1.3.0 */
>      .domainInterfaceStats = libxlDomainInterfaceStats, /* 1.3.2 */
> +    .domainBlockStats = libxlDomainBlockStats, /* 2.1.0 */
> +    .domainBlockStatsFlags = libxlDomainBlockStatsFlags, /* 2.1.0 */
>      .connectDomainEventRegister = libxlConnectDomainEventRegister, /* 0.9.0 */
>      .connectDomainEventDeregister = libxlConnectDomainEventDeregister, /* 0.9.0 */
>      .domainManagedSave = libxlDomainManagedSave, /* 0.9.2 */

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