Messages in this thread | | | Date | Fri, 29 Jan 2010 09:02:44 +0100 | From | Jens Axboe <> | Subject | Re: Added in stricter no merge semantics for block I/O |
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On Tue, Jan 26 2010, Alan D. Brunelle wrote: > Added in stricter no merge semantics for block I/O > > Updated 'nomerges' tunable to accept a value of '2' - indicating that _no_ > merges at all are to be attempted (not even the simple one-hit cache). > > The following table illustrates the additional benefit - 5 minute runs of > a random I/O load were applied to a dozen devices on a 16-way x86_64 system. > > nomerges Throughput %System Improvement (tput / %sys) > -------- ------------ ----------- ------------------------- > 0 12.45 MB/sec 0.669365609 > 1 12.50 MB/sec 0.641519199 0.40% / 2.71% > 2 12.52 MB/sec 0.639849750 0.56% / 2.96% > > Signed-off-by: Alan D. Brunelle <alan.brunelle@hp.com> > Cc: jens.axboe@oracle.com > --- > Documentation/ABI/testing/sysfs-block | 14 ++++++++++++++ > Documentation/block/queue-sysfs.txt | 10 +++++----- > block/blk-sysfs.c | 11 +++++++---- > block/elevator.c | 11 ++++++++++- > include/linux/blkdev.h | 3 +++ > 5 files changed, 39 insertions(+), 10 deletions(-)
Thanks Alan, I think this is a good addition, I have often before hacked up the "no merges at all" logic for testing purposes as well. I have queued it up for 2.6.34.
-- Jens Axboe
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