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    SubjectRe: [PATCH] Optimize struct task_delay_info
    From"Zhang, Yanmin" <>
    DateWed, 18 Jul 2007 12:30:15 +0800
    On Wed, 2007-07-11 at 17:16 +0530, Balbir Singh wrote:
    > Zhang, Yanmin wrote:
    > > struct task_delay_info is used by per process block I/O delay statistics
    > > feature which is useful in kernel. This struct is not optimized.
    > > 
    > > My patch against kernel 2.6.22 shrinks it a half.
    > > 
    > > 1) Delete blkio_start and blkio_end. As the collection happens in
    > > io_schedule and io_schedule_timeout, we use local variables to
    > > replace them;
    > > 2) Delete lock. The change to the protected data has no nested cases.
    > > In addition, the result is for performance data collection, so it’s
    > > unnecessary to add such lock. 
    > > 3) Delete flags. It just has one value. Use the most significant bit of
    > > blkio_delay (64 bits) to mark it..
    > > 
    > > 
    > > Signed-off-by: Zhang Yanmin <yanmin.zhang@intel.com>
    > 
    > Hi, Yanmin,
    > 
    > Did you see any particular performance issues with the delay accounting
    > patches? Is the patch tested; could you please provide test results?
    It's hard to find an appropriate benchmark to test it. Anyway, I used sysbench
    to test it on my x86_64 machine. My machine has 16 logical cpu, dual-core+hyperThread.
    memory is 8GB and disk is one SATA.
    
    I tested both sequence and rand.
    1) seq read/write:use command line:
    echo "3">/proc/sys/vm/drop_caches; sysbench --test=fileio --file-test-mode=seqrewr
    --num-threads=32 --file-total-size=1500M --max-requests=150000 --max-time=3000 run;
    Run the command for 20 times and get average result:
    Without patch: 49.7511Mb/sec
    With patch: 51.6557Mb/sec
    Improvement: 3.8%
    
    
    2) Rand read/write:use command line:
    echo "3">/proc/sys/vm/drop_caches; sysbench --test=fileio --file-test-mode=rndrw
    --num-threads=32 --file-total-size=800M --max-requests=15000 --max-time=3000 run;
    
    Run the command for 10 times and get average result:
    Without patch: 7.25657Mb/sec
    With patch: 7.35052Mb/sec
    Improvement: 1.3%
    
    
    I didn't use application to read the delay accounting info. If I did, I guess the improvement
    is better.
    
    > 
    > Meanwhile, I'll review these patches and I am correcting Shailabh's id
    > to his new email id.
    Thanks.
    
    Yanmin
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