[Cluster-devel] [GFS2 PATCH 0/3] Patches to reduce GFS2 fragmentation

[Bob Peterson <rpeterso@redhat.com>]

Hi,

This is a revised version of my patches to improve GFS2 performance and
reduce GFS2 fragmentation. As suggested by Steve Whitehouse, the first patch
has been modified to base its distribution of resource groups on the number
of journals.

Also as suggested, the patch that kept file close from deleting rgrp
reservations has been removed from the set, leaving only three patches.
The removal of that patch caused fragmentation to climb 15 percent, but it's
still much (41 percent) better than the original stock kernels. I agree that
use cases like untar would make for much worse fragmentation problems if
that patch were to remain.

I've re-tested with these three patches and found that performance and
fragmentation are still good. Here are numbers:

STOCK RHEL7 kernel (none of these patches):

Run times:
Run 1 time: 2hr 40min 33sec
Run 2 time: 2hr 39min 52sec
Run 3 time: 2hr 39min 31sec
Run 4 time: 2hr 33min 57sec
Run 5 time: 2hr 41min 6sec

Total file extents (File fragmentation):
EXTENT COUNT FOR OUTPUT FILES =  744708
EXTENT COUNT FOR OUTPUT FILES =  749868
EXTENT COUNT FOR OUTPUT FILES =  721862
EXTENT COUNT FOR OUTPUT FILES =  635301
EXTENT COUNT FOR OUTPUT FILES =  689263 (Average 708200)

The times are bad and the fragmentation level is also bad. If I add
just the first patch, "GFS2: Set of distributed preferences for rgrps"
the performance improves, but the fragmentation is worse (I only did three
iterations this time):

Run times:
Run 1 time: 2hr 2min 47sec
Run 2 time: 2hr 8min 37sec
Run 3 time: 2hr 10min 0sec

Total file extents (File fragmentation):
EXTENT COUNT FOR OUTPUT FILES =  1011217
EXTENT COUNT FOR OUTPUT FILES =  1025973
EXTENT COUNT FOR OUTPUT FILES =  1070163

With these three patches, both performance and fragmentation are good:

Run 1 time: 2hr 9min 49sec
Run 2 time: 2hr 10min 15sec
Run 3 time: 2hr 8min 35sec
Run 4 time: 2hr 15min 15sec
Run 5 time: 2hr 7min 4sec
Run 6 time: 2hr 8min 8sec
Run 7 time: 2hr 7min 54sec

EXTENT COUNT FOR OUTPUT FILES =  406366
EXTENT COUNT FOR OUTPUT FILES =  432978
EXTENT COUNT FOR OUTPUT FILES =  428736
EXTENT COUNT FOR OUTPUT FILES =  419736
EXTENT COUNT FOR OUTPUT FILES =  419040
EXTENT COUNT FOR OUTPUT FILES =  422774
EXTENT COUNT FOR OUTPUT FILES =  409281 (Average 419844)

Regards,

Bob Peterson
Red Hat File Systems

Signed-off-by: Bob Peterson <rpeterso@redhat.com> 
---
Bob Peterson (3):
  GFS2: Set of distributed preferences for rgrps
  GFS2: Only increase rs_sizehint
  GFS2: If we use up our block reservation, request more next time

 fs/gfs2/file.c   |  3 ++-
 fs/gfs2/incore.h |  1 +
 fs/gfs2/rgrp.c   | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
 fs/gfs2/rgrp.h   |  1 +
 4 files changed, 68 insertions(+), 6 deletions(-)

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1.9.3