[Xen-devel] [PATCH]: Fix libxenstat statistics for blktap disks on linux

["steven maresca" <steve.maresca@xxxxxxxxx>]

Overview: update xenstat vbd statistics parsing from /sys/devices/xen-backend to process blktap disks

Reason: 
        -blktap devices (now referenced as tap rather than vbd in /sys) have statistics counters
                (e.g.,  rd_req, wr_req, oo_req) prepended by tap_
        -xenstat behavior did not previously account for this behavior, which resulted in 0 disks
                visible and similarly impacted disk statistics

To reproduce these conditions, make a domain with tap:aio backed disks on 3.2.x, run xentop, and
        press B to view VBD stats (nothing will appear for the domain using tap:aio )


Steve Maresca

Signed-off-by: steve.maresca@xxxxxxxxx

diff -r b320cfe1f10f -r be6917832779 tools/xenstat/libxenstat/src/xenstat_linux.c
--- a/tools/xenstat/libxenstat/src/xenstat_linux.c    Thu Jun 05 13:04:07 2008 +0100
+++ b/tools/xenstat/libxenstat/src/xenstat_linux.c    Mon Jun 09 16:34:11 2008 -0400
@@ -181,6 +181,12 @@ int xenstat_collect_vbds(xenstat_node * 
     struct dirent *dp;
     struct priv_data *priv = get_priv_data(node->handle);
 
+    char *sys_prefix = "statistics/";
+
+    /* 23 = "statistics/" + "xxxx_xx_req" */
+    char ooreq[23], rdreq[23], wrreq[23]; 
+    char *stat_prefix = NULL;
+
     if (priv == NULL) {
         perror("Allocation error");
         return 0;
@@ -208,12 +214,16 @@ int xenstat_collect_vbds(xenstat_node * 
         if (ret != 3)
             continue;
 
-        if (strcmp(buf,"vbd") == 0)
+
+        if (strcmp(buf,"vbd") == 0){
+            stat_prefix = "";
             vbd.back_type = 1;
-        else if (strcmp(buf,"tap") == 0)
+        } else if (strcmp(buf,"tap") == 0){
+            stat_prefix = "tap_";
             vbd.back_type = 2;
-        else
-            continue;
+        } else {
+            continue;
+        }
 
         domain = xenstat_node_domain(node, domid);
         if (domain == NULL) {
@@ -224,24 +234,26 @@ int xenstat_collect_vbds(xenstat_node * 
             continue;
         }
 
-        if((read_attributes_vbd(dp->d_name, "statistics/oo_req", buf, 256)<=0)
+        snprintf(ooreq, sizeof(ooreq), "%s%soo_req", sys_prefix, stat_prefix);
+        if((read_attributes_vbd(dp->d_name, ooreq, buf, 256)<=0)
            || ((ret = sscanf(buf, "%llu", &vbd.oo_reqs)) != 1))
         {
             continue;
         }
 
-        if((read_attributes_vbd(dp->d_name, "statistics/rd_req", buf, 256)<=0)
+        snprintf(rdreq,  sizeof(rdreq),"%s%srd_req", sys_prefix, stat_prefix);
+        if((read_attributes_vbd(dp->d_name, rdreq, buf, 256)<=0)
            || ((ret = sscanf(buf, "%llu", &vbd.rd_reqs)) != 1))
         {
             continue;
         }
 
-        if((read_attributes_vbd(dp->d_name, "statistics/wr_req", buf, 256)<=0)
+        snprintf(wrreq,  sizeof(wrreq),"%s%swr_req", sys_prefix, stat_prefix);
+        if((read_attributes_vbd(dp->d_name, wrreq, buf, 256)<=0)
            || ((ret = sscanf(buf, "%llu", &vbd.wr_reqs)) != 1))
         {
             continue;
         }
-
 
         if (domain->vbds == NULL) {
             domain->num_vbds = 1;

xenstat-update
Description: Binary data

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