Re: [libvirt] [PATCH v5] 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 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. 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(a)oracle.com&gt; --- Changes since v4: - No need to handle virtpath as devid - return id = -1 instead - Rework compilation of BlockStatsVBD compilation on other platforms. - Use disk->dst as opposed to plain path to also cover the case when input virtpath is path to file. Before it was returning "cannot find device number" 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 | 367 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 367 insertions(+) diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c index f153f69..b33c898 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 +5052,350 @@ libxlDomainGetJobStats(virDomainPtr dom, } static int +libxlDiskPathToID(const char *virtpath) +{ + static char const* drive_prefix[] = {"xvd", "hd", "sd"}; + int disk, partition, chrused; + int fmt, id; + 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: /* invalid */ + 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) { + 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; +} + +#ifdef __linux__ +static int +libxlDomainBlockStatsVBD(virDomainObjPtr vm, + const char *dev, + libxlBlockStatsPtr stats) +{ + int ret = -1; + int devno = libxlDiskPathToID(dev); + int size = libxlDiskSectorSize(vm->def->id, devno);