Xen devel - Jun 2007 - [PATCH][XENTOP][0/4] Display blktap statistics.

Hi.

These patches add the output function for blktap statistics into xentop.
Currently, xentop outputs only blkback statistics, and not blktap statistics.
By these patches, xentop is made cover both blkback and blktap.

In xen, back-end driver has two types; blkback and blktap.
Blkback driver is old back-end driver.
Blktap driver is new back-end driver and is recommended currently.
Usage of both drivers is same, but xentop outputs only blkback statistics.
Therefore, These patches make xentop output statistics of both blkback and
blktap.

These patches include two part as follows.
1. Unification of sysfs entries'' names
2. Output of statistics about blkback and blktap into xentop.


1. The name of sysfs entries are unified for VBDs.
    Currently, sysfs entries'' names of back-end drivers is specified
"<I/O operation type>_<unit of statistics>".
    For example, in the case that a operation is "READ" and that units
is the number of requests, sysfs entries'' name is "rd-req".
    In addition, in the case of blktap, entries'' names add prefix
"tap_".
    In above example, entries'' name is "tap_rd_req".
    The prefix is redundant.
    The word "tap-" in the directory name is sufficient to distinguish
VBD types.
    Therefore, it is better to remove the prefix "tap_" in sysfs
entries of blktap.

    For example, currently sysfs entries are named as follows.

  [root@xenmachine1 ~]# ls /sys/devices/xen-backend/vbd-1-51712/statistics/
  br_req  oo_req  rd_req  rd_sect  wr_req  wr_sect
  [root@xenmachine1 ~]# ls /sys/devices/xen-backend/tap-2-51712/statistics/
  tap_oo_req  tap_rd_req  tap_rd_sect  tap_wr_req  tap_wr_sect
      
    After applying these patches, names of sysfs entries are changed as follows.

  [root@xenmachine1 ~]# ls /sys/devices/xen-backend/vbd-1-51712/statistics/
  br_req  oo_req  rd_req  rd_sect  wr_req  wr_sect
  [root@xenmachine1 ~]# ls /sys/devices/xen-backend/tap-2-51712/statistics/
  oo_req  rd_req  rd_sect  wr_req  wr_sect


2. Xentop (and libxenstat) collects and outputs statistics of both blkback and
blktap drivers.
    VBDS and VBD_xx fields mean the number of VBDs and a total statistical
amount of them, respectively.
    In detail view lines, xentop outputs statistics about each VBD, namely each
thread of blkback and blktap.
    In addition, in order to identify driver types, type field is added into
detail view lines.
    The type field describes VBD types; "BlkBack" means usage of
blkback driver and "BlkTap" means usage of blktap driver.

   For example,

xentop - 11:46:40   Xen 3.0-unstable
 3 domains: 1 running, 2 blocked, 0 paused, 0 crashed, 0 dying, 0 shutdown
 Mem: 1023220k total, 1022428k used, 792k free    CPUs: 2 @ 2658MHz
       NAME  STATE   CPU(sec) CPU(%)     MEM(k) MEM(%)  MAXMEM(k) MAXMEM(%)
VCPUS NETS NETTX(k) NETRX(k) VBDS   VBD_OO   VBD_RD   VBD_WR SSID
   Domain-0 -----r        725    3.4     729088   71.3   no limit       n/a    
2    4       21       22    0        0        0        0    0
     FC6PVM --b---         62    0.1     131072   12.8     131072      12.8    
2    1       10       16    1        0    20537     9600    0
 VBD BlkTap 51712  [ca: 0]  OO:        0   RD:    20537   WR:     9600
    FC6PVM2 --b---         63    0.1     131072   12.8     131072      12.8    
2    1       19       30    1        0    20490     9847    0
 VBD BlkBack 51712  [ca: 0]  OO:        0   RD:    20490   WR:     9847


 --------------------------------------------------
 Satoshi UCHIDA 
    NEC Corporation, Japan


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