Hi,
during a performance analysis and tuning session, I did some profiling with
oprofile on GFS and dlm.
I got some weird results ...
The installed software is:
RHEL4u5, kernel 2.6.9-55.0.2.ELsmp
GFS: 2.6.9-72.2.0.2
DLM: 2.6.9-46.16.0.1
The configuration includes 2 clusternodes.
I put the following load on one cluster node:
100 processes are doing in parallel:
- create 1000 files with 100kb size each (ie altogether we have 100.000 files)
- flock 1000 files
- unlink 1000 files.
The following oprofile output shows, that the system spends about 49%
(75%*65%*) of the time in gfs_unlinked_get.
Looking into the code whe can see, that this is related to unlinked.c:
53 9394211 58.7081 : ul = list_entry(tmp, struct
gfs_unlinked, ul_list);
It can also be observed, that dlm spends more than 50% of its time in
searching for hashes...
Is this the expected behaviour or can this be tuned somewhere ?
Thanks,
Mark
oprofile shows the following:
# opreport --long-filenames --threshold 1
samples| %|
------------------
168187984 75.4905 /gfs
37896161 17.0095 /usr/lib/debug/lib/modules/2.6.9-55.0.2.ELsmp/vmlinux
11686302 5.2453 /dlm
# opreport image:/gfs -l --threshold 1
110838927 65.8899 gfs_unlinked_get
12918468 7.6796 gfs_unlinked_hold
10958430 6.5144 scan_glock
9448317 5.6167 examine_bucket
5504188 3.2720 gfs_unlinked_unlock
3795382 2.2562 trylock_on_glock
3368017 2.0022 unlock_on_glock
1939971 1.1532 run_queue
# opreport image:/dlm -l --threshold 1
samples % symbol name
5853674 50.0875 search_hashchain
3726276 31.8842 search_bucket
1506327 12.8890 __find_lock_by_id
--
Gruss / Regards,
Dipl.-Ing. Mark Hlawatschek
http://www.atix.de/
http://www.open-sharedroot.org/
**
ATIX Informationstechnologie und Consulting AG
Einsteinstr. 10
85716 Unterschleissheim
Deutschland/Germany
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