[libvirt] [PATCH 1/1] virsh nodecpustats erroneously returns stats for offline cpus on Linux

Bing Bu Cao mars at linux.vnet.ibm.com
Thu Dec 19 08:40:34 UTC 2013


On 12/19/2013 12:40 PM, Pradipta Kr. Banerjee wrote:
> From: "Pradipta Kr. Banerjee" <bpradip at in.ibm.com>
>
> virsh nodecpustats erroneously returns stats for offline cpus on Linux
>
> To retrieve node cpu statistics on Linux system, the
> linuxNodeGetCPUstats function performs a minimal match of the input
> cpuid with the cpuid read from /proc/cpustat. On systems with larger
> cpus this can result in erroneous data.
> For eg if /proc/stat has similar data
>   cpu  3645648 485 361475 3691194868 176595 40645 69850 0 1526172 0
>   cpu0 494045 62 42763 138516619 16107 2339 2431 0 248345 0
>   cpu4 402646 59 34745 138617562 17738 1413 1196 0 193948 0
>   cpu8 318662 32 32119 138715131 7903 927 982 0 115429 0
>   cpu12 247004 33 30465 138791438 5251 759 913 0 51938 0
>
> and cpu 1,2 are offline, then
>
> 'virsh nodecpustats 1' displays data for cpu12
>
> whereas virsh nodecpustats 2 correctly throws the following error
>
> "error: Unable to get node cpu stats
> error: Invalid cpuNum in linuxNodeGetCPUStats"
>
> This patch fixes the above mentioned problem
>
> Signed-off-by: Pradipta Kr. Banerjee <bpradip at in.ibm.com>
> ---
>   src/nodeinfo.c | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
>
> diff --git a/src/nodeinfo.c b/src/nodeinfo.c
> index 1838547..c9e5ff1 100644
> --- a/src/nodeinfo.c
> +++ b/src/nodeinfo.c
> @@ -614,6 +614,8 @@ linuxNodeGetCPUStats(FILE *procstat,
>       unsigned long long usr, ni, sys, idle, iowait;
>       unsigned long long irq, softirq, steal, guest, guest_nice;
>       char cpu_header[3 + INT_BUFSIZE_BOUND(cpuNum)];
> +    char cpu_header_read[3 + INT_BUFSIZE_BOUND(cpuNum)];
> +    char cpu_header_fmt[8];
>
>       if ((*nparams) == 0) {
>           /* Current number of cpu stats supported by linux */
> @@ -631,8 +633,11 @@ linuxNodeGetCPUStats(FILE *procstat,
>
>       if (cpuNum == VIR_NODE_CPU_STATS_ALL_CPUS) {
>           strcpy(cpu_header, "cpu");
> +        snprintf(cpu_header_fmt, sizeof(cpu_header_fmt), "%%%ds", 3);
>       } else {
>           snprintf(cpu_header, sizeof(cpu_header), "cpu%d", cpuNum);
> +        snprintf(cpu_header_fmt, sizeof(cpu_header_fmt), "%%%ds",
> +                 (int)(3 + INT_BUFSIZE_BOUND(cpuNum)));
>       }
>
>       while (fgets(line, sizeof(line), procstat) != NULL) {
> @@ -649,6 +654,14 @@ linuxNodeGetCPUStats(FILE *procstat,
>                   continue;
>               }
>
> +            /*
> +             * Process with stats gathering only if the cpuid from /proc/stat
> +             * matches exactly with the input cpuid
> +            */
> +            sscanf(buf, cpu_header_fmt, cpu_header_read);
> +            if (STRNEQ(cpu_header, cpu_header_read))
> +                continue;
> +
>               for (i = 0; i < *nparams; i++) {
>                   virNodeCPUStatsPtr param = &params[i];
I think we can use strsplit() to handle this bug easily.

diff --git a/src/nodeinfo.c b/src/nodeinfo.c
index 1838547..aa1ad81 100644
--- a/src/nodeinfo.c
+++ b/src/nodeinfo.c
@@ -637,8 +637,9 @@ linuxNodeGetCPUStats(FILE *procstat,

       while (fgets(line, sizeof(line), procstat) != NULL) {
           char *buf = line;
+        char **buf_header = virStringSplit(buf, " ", 2);

-        if (STRPREFIX(buf, cpu_header)) { /* aka logical CPU time */
+        if (STREQ(buf_header[0], cpu_header)) { /* aka logical CPU time */
               size_t i;

               if (sscanf(buf,
@@ -697,6 +698,7 @@ linuxNodeGetCPUStats(FILE *procstat,
               ret = 0;
               goto cleanup;
           }
+        virStringFreeList(buf_header);
       }

       virReportInvalidArg(cpuNum,
>
> --
> 1.8.3.1
>
> --
> libvir-list mailing list
> libvir-list at redhat.com
> https://www.redhat.com/mailman/listinfo/libvir-list
>


-- 
Best Regards,
Bing Bu Cao




More information about the libvir-list mailing list