Re: [libvirt] [PATCH 2/3] Qemu: add CMT support

One RFC in https://www.redhat.com/archives/libvir-list/2015-June/msg01509.html CMT (Cache Monitoring Technology) can be used to measure the usage of cache by VM running on the host. This patch will extend the bulk stats API (virDomainListGetStats) to add this field. Applications based on libvirt can use this API to achieve cache usage of VM. Because CMT implementation in Linux kernel is based on perf mechanism, this patch will enable perf event for CMT when VM is created and disable it when VM is destroyed. Signed-off-by: Qiaowei Ren <qiaowei.ren(a)intel.com&gt;

diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h index 54e1e7b..31bce33 100644 --- a/src/qemu/qemu_domain.h +++ b/src/qemu/qemu_domain.h @@ -196,6 +196,9 @@ struct _qemuDomainObjPrivate { bool hookRun; /* true if there was a hook run over this domain */ + int cmt_fd; /* perf handler for CMT */ + + /* Bitmaps below hold data from the auto NUMA feature */ virBitmapPtr autoNodeset; virBitmapPtr autoCpuset; diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 4cfae03..8c678c9 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -19320,6 +19320,53 @@ qemuDomainGetStatsBlock(virQEMUDriverPtr driver, #undef QEMU_ADD_COUNT_PARAM +static int +qemuDomainGetStatsCache(virQEMUDriverPtr driver ATTRIBUTE_UNUSED, + virDomainObjPtr dom, + virDomainStatsRecordPtr record, + int *maxparams, + unsigned int privflags ATTRIBUTE_UNUSED) +{ + qemuDomainObjPrivatePtr priv = dom->privateData; + FILE *fd; + unsigned long long cache = 0; + int scaling_factor = 0; + + if (priv->cmt_fd <= 0) + return -1; + + if (read(priv->cmt_fd, &cache, sizeof(uint64_t)) < 0) { + virReportSystemError(errno, "%s", + _("Unable to read cache data")); + return -1; + } + + fd = fopen("/sys/devices/intel_cqm/events/llc_occupancy.scale", "r"); + if (!fd) { + virReportSystemError(errno, "%s", + _("Unable to open CMT scale file")); + return -1; + } + if (fscanf(fd, "%d", &scaling_factor) != 1) { + virReportSystemError(errno, "%s", + _("Unable to read CMT scale file")); + VIR_FORCE_FCLOSE(fd); + return -1; + } + VIR_FORCE_FCLOSE(fd); + + cache *= scaling_factor; + + if (virTypedParamsAddULLong(&record->params, + &record->nparams, + maxparams, + "cache.current", + cache) < 0) + return -1; + + return 0; +} + typedef int (*qemuDomainGetStatsFunc)(virQEMUDriverPtr driver, virDomainObjPtr dom, @@ -19340,6 +19387,7 @@ static struct qemuDomainGetStatsWorker qemuDomainGetStatsWorkers[] = { { qemuDomainGetStatsVcpu, VIR_DOMAIN_STATS_VCPU, false }, { qemuDomainGetStatsInterface, VIR_DOMAIN_STATS_INTERFACE, false }, { qemuDomainGetStatsBlock, VIR_DOMAIN_STATS_BLOCK, true }, + { qemuDomainGetStatsCache, VIR_DOMAIN_STATS_CACHE, false }, { NULL, 0, false } }; diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c index ba84182..00b889d 100644 --- a/src/qemu/qemu_process.c +++ b/src/qemu/qemu_process.c @@ -25,8 +25,11 @@ #include <unistd.h> #include <signal.h> #include <sys/stat.h> +#include <sys/ioctl.h> +#include <sys/syscall.h> #if defined(__linux__) # include <linux/capability.h> +# include <linux/perf_event.h> #elif defined(__FreeBSD__) # include <sys/param.h> # include <sys/cpuset.h> @@ -4274,6 +4277,75 @@ qemuLogOperation(virDomainObjPtr vm, goto cleanup; } +/* + * Enable CMT(Cache Monitoring Technology) to measure the usage of + * cache by VM running on the node. + * + * Because the hypervisor implement CMT support basedon perf mechanism, + * we should enable perf event for CMT. The function 'sys_erf_event_open' + * is perf syscall wrapper. + */ +#ifdef __linux__ +static long sys_perf_event_open(struct perf_event_attr *hw_event, + pid_t pid, int cpu, int group_fd, + unsigned long flags) +{ + return syscall(__NR_perf_event_open, hw_event, pid, cpu, + group_fd, flags); +} +static int qemuCmtEnable(virDomainObjPtr vm) +{ + qemuDomainObjPrivatePtr priv = vm->privateData; + struct perf_event_attr cmt_attr; + int event_type; + FILE *fp; + + fp = fopen("/sys/devices/intel_cqm/type", "r"); + if (!fp) { + virReportSystemError(errno, "%s", + _("CMT is not available on this host")); + return -1; + } + if (fscanf(fp, "%d", &event_type) != 1) { + virReportSystemError(errno, "%s", + _("Unable to read event type file.")); + VIR_FORCE_FCLOSE(fp); + return -1; + } + VIR_FORCE_FCLOSE(fp); + + memset(&cmt_attr, 0, sizeof(struct perf_event_attr)); + cmt_attr.size = sizeof(struct perf_event_attr); + cmt_attr.type = event_type; + cmt_attr.config = 1; + cmt_attr.inherit = 1; + cmt_attr.disabled = 1; + cmt_attr.enable_on_exec = 0; + + priv->cmt_fd = sys_perf_event_open(&cmt_attr, vm->pid, -1, -1, 0); + if (priv->cmt_fd < 0) { + virReportSystemError(errno, + _("Unable to open perf type=%d for pid=%d"), + event_type, vm->pid); + return -1; + } + + if (ioctl(priv->cmt_fd, PERF_EVENT_IOC_ENABLE) < 0) { + virReportSystemError(errno, "%s", + _("Unable to enable perf event for CMT")); + return -1; + } + + return 0; +} +#else +static int qemuCmtEnable(virDomainObjPtr vm) +{ + virReportUnsupportedError(); + return -1; +} +#endif + int qemuProcessStart(virConnectPtr conn, virQEMUDriverPtr driver, virDomainObjPtr vm, @@ -4954,6 +5026,11 @@ int qemuProcessStart(virConnectPtr conn, if (virDomainSaveStatus(driver->xmlopt, cfg->stateDir, vm) < 0) goto cleanup; + VIR_DEBUG("Setting CMT perf counter"); + if (qemuCmtEnable(vm) < 0) + virReportSystemError(errno, "%s", + _("CMT is not available on this host")); + /* finally we can call the 'started' hook script if any */ if (virHookPresent(VIR_HOOK_DRIVER_QEMU)) { char *xml = qemuDomainDefFormatXML(driver, vm->def, 0); @@ -5122,6 +5199,15 @@ void qemuProcessStop(virQEMUDriverPtr driver, virPortAllocatorRelease(driver->migrationPorts, priv->nbdPort); priv->nbdPort = 0; + /* Disable CMT */ + if (priv->cmt_fd > 0) { + if (ioctl(priv->cmt_fd, PERF_EVENT_IOC_DISABLE) < 0) { + virReportSystemError(errno, "%s", + _("Unable to disable perf event for CMT")); + } + VIR_FORCE_CLOSE(priv->cmt_fd); + } + if (priv->agent) { qemuAgentClose(priv->agent); priv->agent = NULL;