On Mon, Feb 11, 2013 at 7:02 PM, Pranith
Kumar K
<pkarampu@xxxxxxxxxx>
wrote:
hi,
Problem:
When there are multiple fds writing to same file with
eager-lock enabled, the fd which acquires the eager-lock waits
for
post-op-delay secs before doing the unlock. Because of this
all other fds opened on the file face extra delay when
performing writes. Eager-locking, post-op-delay need to be
disabled when there are multiple fds opened on the file.
Here is the profile info output for the case above:
Execute the following command on the mount point.
for n in `seq 1 50` ; do eval "/home/pranithk/workspace/gerrit-repo/append2log.py
./ben.log 10000 0.001 &" ; done ; wait
%-latency Avg-latency Min-Latency Max-Latency No. of
calls Fop
--------- ----------- ----------- -----------
------------ ----
0.00 0.00 us 0.00 us 0.00 us
50 RELEASE
0.00 0.00 us 0.00 us 0.00 us
60 RELEASEDIR
0.00 55.00 us 55.00 us 55.00 us
1 GETXATTR
0.00 31.50 us 27.00 us 36.00 us
2 STATFS
0.00 41.00 us 29.00 us 53.00 us
2 ENTRYLK
0.00 198.00 us 198.00 us 198.00 us
1 CREATE
0.00 124.00 us 108.00 us 140.00 us
2 READDIR
0.00 27.04 us 17.00 us 95.00 us
49 OPEN
0.00 74.89 us 13.00 us 206.00 us
47 STAT
0.01 87.02 us 11.00 us 391.00 us
50 FLUSH
0.01 102.43 us 20.00 us 268.00 us
60 OPENDIR
0.02 344.27 us 22.00 us 940.00 us
44 WRITE
0.02 228.80 us 52.00 us 345.00 us
82 FXATTROP
0.03 199.89 us 19.00 us 404.00 us
120 READDIRP
0.05 91.41 us 23.00 us 832.00 us
421 LOOKUP
99.86 632698.45 us 17.00 us 1999724.00 us
126 FINODELK
Observe that most of the delay is in FINODELK fop.
Possible Solution:
With the patch: http://review.gluster.org/4468
we started maintaining open-fd count in the inode. We need to
implement xdata based xattr retrieval in write-fop and get
open-fd-count in write fop. Remember the open-fd-count
received from the write-fops and maintain it in afr-fd-ctx. If
the open-fd count is >1 post-op-delay is immediately
disabled for that write fop. All write-fops take into
consideration this count to determine whether to enable
eager-lock, post-op-delay for that write fop.
Let me know if you foresee any issues with this approach.
https://bugzilla.redhat.com/show_bug.cgi?id=910217
is tracking this issue.
Ideally you would want open-fd count to be retrieved in all
fops, and only when an eager lock has been acquired. Any fop
callback's xattr_rsp inspection should potentially wake up the
sleeping post-op-delay in that inode (and disable further
eager locking temporarily).
Avati
