Re: [libvirt] [PATCHv3 1/4] util: Introduce monitor capability interface

-----Original Message----- From: John Ferlan [mailto:jferlan@redhat.com] Sent: Friday, September 21, 2018 12:16 AM To: Wang, Huaqiang <huaqiang.wang(a)intel.com>; libvir-list(a)redhat.com Cc: Feng, Shaohe <shaohe.feng(a)intel.com>; Niu, Bing <bing.niu(a)intel.com>; Ding, Jian-feng <jian-feng.ding(a)intel.com>; Zang, Rui <rui.zang(a)intel.com&gt; Subject: Re: [PATCHv3 1/4] util: Introduce monitor capability interface On 09/20/2018 06:10 AM, Wang Huaqiang wrote: > This patch introduces the resource monitor and creates the interface > for getting host capability of resource monitor from the system > resource control file system. > > The resource monitor takes the role of RDT monitoring group and could > be used to monitor the resource consumption information, such as the > last level cache occupancy and the utilization of memory bandwidth. > > Signed-off-by: Wang Huaqiang <huaqiang.wang(a)intel.com&gt; > Reviewed-by: John Ferlan <jferlan(a)redhat.com&gt; > --- > src/util/virresctrl.c | 126 > ++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 126 insertions(+) [...] > + * Retrieve monitor capability from the resource control file system. > + * > + * The monitor capability is exposed through "SYSFS_RESCTRL_PATH/info/L3_MON" > + * directory under the resource control file system. The monitor > +capability is > + * parsed by reading the interface files and stored in the structure > + * 'virResctrlInfoMongrp'. > + * > + * Not all host supports the resource monitor, leave the pointer > + * @resctrl->monitor_info empty if not supported. > + */ > +static int > +virResctrlGetMonitorInfo(virResctrlInfoPtr resctrl) { > + int ret = -1; > + int rv = -1; > + char *featurestr = NULL; > + char **features = NULL; > + size_t nfeatures = 0; > + virResctrlInfoMongrpPtr info_monitor = NULL; > + > + if (VIR_ALLOC(info_monitor) < 0) > + return -1; > + > + /* For now, monitor only exists in level 3 cache */ > + info_monitor->cache_level = 3; > + > + rv = virFileReadValueUint(&info_monitor->max_monitor, > + SYSFS_RESCTRL_PATH "/info/L3_MON/num_rmids"); > + if (rv == -2) { > + /* The file doesn't exist, so it's unusable for us, probably resource > + * monitor unsupported */ > + VIR_INFO("The path '" SYSFS_RESCTRL_PATH "/info/L3_MON/num_rmids' " I changed "path" to "file" to be consistent with he message below. > + "does not exist"); > + ret = 0; > + virResetLastError(); Upon further reflection since it wasn't in the next Uint call -2 failure handling, I guess this isn't necessary, but I'll leave it just in case something does slip in there in the future... > + goto cleanup; > + } else if (rv < 0) { > + /* Other failures are fatal, so just quit */ > + goto cleanup; > + } > + > + rv = virFileReadValueUint(&info_monitor->cache_reuse_threshold, > + SYSFS_RESCTRL_PATH > + "/info/L3_MON/max_threshold_occupancy"); > + if (rv == -2) { > + /* If CMT is not supported, then 'max_threshold_occupancy' file > + * will not exist. */ > + VIR_INFO("File '" SYSFS_RESCTRL_PATH > + "/info/L3_MON/max_threshold_occupancy' does not > + exist"); I think this should be a VIR_DEBUG, as in is it really that important unless you're debugging... and although I now think it'd be unnecessary I'll add the virResetLastError here. > + } else if (rv < 0) { > + goto cleanup; > + } > + > + rv = virFileReadValueString(&featurestr, > + SYSFS_RESCTRL_PATH > + "/info/L3_MON/mon_features"); > + if (rv == -2) > + virReportError(VIR_ERR_INTERNAL_ERROR, "%s", > + _("Cannot get mon_features from resctrl")); > + if (rv < 0) > + goto cleanup; > + > + if (!*featurestr) { > + /* If no feature found in "/info/L3_MON/mon_features", > + * some error happens */ > + virReportError(VIR_ERR_INTERNAL_ERROR, "%s", > + _("Get empty feature list from resctrl")); > + ret = -1; The ret = -1; is unnecessary. I think you missed my point. The rv == -2 up a bit does change it, but it goes to cleanup. I'll remove it. I'll fix up things before I push. Just let me know if the VIR_DEBUG is fine or if you prefer to keep VIR_INFO. It's not that important other than you know you're going to get the message and seeing it as "INFO" could alarm someone, so changing to DEBUG means someone could still see the message and perhaps figure out why the value is 0 in their output instead of something "real".

John [...]