[Bugs] [Bug 1409206] New: Extra lookup/ fstats are sent over the network when a brick is down.

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1409206

            Bug ID: 1409206
           Summary: Extra lookup/fstats are sent over the network when a
                    brick is down.
           Product: GlusterFS
           Version: mainline
         Component: replicate
          Assignee: bugs at gluster.org
          Reporter: ravishankar at redhat.com
                CC: bugs at gluster.org



Description of problem:
When a brick is killed in a replica and `dd` is run, we see a lot of fstats
being sent over the network, with a small (but very real) reduction in write
throughput.

Throughput and profile info on a random brick when all bricks are up:
==================================================================
root at tuxpad fuse_mnt$ dd if=/dev/zero of=FILE bs=1024 count=10240
10240+0 records in
10240+0 records out
10485760 bytes (10 MB) copied, 2.9847 s, 3.5 MB/s
Brick: 127.0.0.2:/home/ravi/bricks/brick1
-----------------------------------------
Cumulative Stats:
   Block Size:               1024b+ 
 No. of Reads:                    0 
No. of Writes:                10240 
 %-latency   Avg-latency   Min-Latency   Max-Latency   No. of calls         Fop
 ---------   -----------   -----------   -----------   ------------        ----
      0.00       0.00 us       0.00 us       0.00 us              2     RELEASE
      0.00       0.00 us       0.00 us       0.00 us              6  RELEASEDIR
      0.01      30.50 us      27.00 us      34.00 us              2     INODELK
      0.01      70.00 us      70.00 us      70.00 us              1        OPEN
      0.01      35.50 us      19.00 us      52.00 us              2       FLUSH
      0.03      96.50 us      83.00 us     110.00 us              2    GETXATTR
      0.04     253.00 us     253.00 us     253.00 us              1    TRUNCATE
      0.07     225.50 us     202.00 us     249.00 us              2    FXATTROP
      0.15     153.17 us      47.00 us     656.00 us              6      STATFS
      0.17     537.00 us     207.00 us     867.00 us              2     XATTROP
      0.22     685.00 us      22.00 us    1348.00 us              2    FINODELK
      0.62     255.67 us     104.00 us     928.00 us             15      LOOKUP
     98.66      59.72 us      35.00 us    4772.00 us          10240       WRITE

    Duration: 673 seconds                                                       
   Data Read: 0 bytes                                                           
Data Written: 10485760 bytes         


Throughput and profile info of one of the 'up' bricks when one brick is down
===========================================================================
0:root at tuxpad fuse_mnt$ dd if=/dev/zero of=FILE bs=1024 count=10240
10240+0 records in
10240+0 records out
10485760 bytes (10 MB) copied, 4.24494 s, 2.5 MB/s

Brick: 127.0.0.2:/home/ravi/bricks/brick1
-----------------------------------------
Cumulative Stats:
   Block Size:               1024b+
 No. of Reads:                    0
No. of Writes:                10240
 %-latency   Avg-latency   Min-Latency   Max-Latency   No. of calls         Fop
 ---------   -----------   -----------   -----------   ------------        ----
      0.00       0.00 us       0.00 us       0.00 us              2     RELEASE
      0.00       0.00 us       0.00 us       0.00 us              5  RELEASEDIR
      0.01      98.00 us      98.00 us      98.00 us              1        OPEN
      0.01      57.50 us      43.00 us      72.00 us              2     INODELK
      0.01     126.00 us     126.00 us     126.00 us              1    GETXATTR
      0.02     184.00 us     184.00 us     184.00 us              1    TRUNCATE
      0.02     113.00 us     109.00 us     117.00 us              2    FXATTROP
      0.02     122.00 us      16.00 us     228.00 us              2       FLUSH
      0.02     132.00 us      38.00 us     226.00 us              2    FINODELK
      0.08     418.00 us     283.00 us     553.00 us              2     XATTROP
      0.21     763.00 us     122.00 us    1630.00 us              3      LOOKUP
     41.23      44.83 us      36.00 us     490.00 us          10240       WRITE
     58.38      63.47 us      46.00 us     888.00 us          10240       FSTAT

    Duration: 75 seconds
   Data Read: 0 bytes
Data Written: 10485760 bytes

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