lkml.org 
[lkml]   [2007]   [Sep]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Scheduler benchmarks - a follow-up
    On 9/17/07, Ingo Molnar <mingo@elte.hu> wrote:
    >
    > * Rob Hussey <robjhussey@gmail.com> wrote:
    >
    > > http://www.healthcarelinen.com/misc/benchmarks/BOUND_hackbench_benchmark2.png
    >
    > heh - am i the only one impressed by the consistency of the blue line in
    > this graph? :-) [ and the green line looks a bit like a .. staircase? ]
    >
    > i've meanwhile tested hackbench 90 and the performance difference
    > between -ck and -cfs-devel seems to be mostly down to the more precise
    > (but slower) sched_clock() introduced in v2.6.23 and to the startup
    > penalty of freshly created tasks.
    >
    > Putting back the 2.6.22 version and tweaking the startup penalty gives
    > this:
    >
    > [hackbench 90, smaller is better]
    >
    > sched-devel.git sched-devel.git+lowres-sched-clock+dsp
    > --------------- --------------------------------------
    > 5.555 5.149
    > 5.641 5.149
    > 5.572 5.171
    > 5.583 5.155
    > 5.532 5.111
    > 5.540 5.138
    > 5.617 5.176
    > 5.542 5.119
    > 5.587 5.159
    > 5.553 5.177
    > --------------------------------------
    > avg: 5.572 avg: 5.150 (-8.1%)
    >
    > ('lowres-sched-clock' is the patch i sent in the previous mail. 'dsp' is
    > a disable-startup-penalty patch that is in the latest sched-devel.git)
    >
    > i have used your .config to conduct this test.
    >
    > can you reproduce this with the (very-) latest sched-devel git tree:
    >
    > git-pull git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-sched-devel.git
    >
    > plus with the low-res-sched-clock patch (re-) attached below?
    >
    > Ingo
    > ---
    > arch/i386/kernel/tsc.c | 4 ++--
    > 1 file changed, 2 insertions(+), 2 deletions(-)
    >
    > Index: linux/arch/i386/kernel/tsc.c
    > ===================================================================
    > --- linux.orig/arch/i386/kernel/tsc.c
    > +++ linux/arch/i386/kernel/tsc.c
    > @@ -110,9 +110,9 @@ unsigned long long native_sched_clock(vo
    > * very important for it to be as fast as the platform
    > * can achive it. )
    > */
    > - if (unlikely(!tsc_enabled && !tsc_unstable))
    > + if (1 || unlikely(!tsc_enabled && !tsc_unstable))
    > /* No locking but a rare wrong value is not a big deal: */
    > - return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
    > + return jiffies_64 * (1000000000 / HZ);
    >
    > /* read the Time Stamp Counter: */
    > rdtscll(this_offset);
    > -

    Sorry it took so long for me to get back.

    Ok, to start the dmesg output for 2.6.22-ck1 is attached. The relevant
    lines seem to be:
    [ 27.691348] checking TSC synchronization [CPU#0 -> CPU#1]: passed.
    [ 27.995427] Time: tsc clocksource has been installed.

    I've updated to the latest sched-devel git, and applied the patch
    above. I ran it through the same tests, but this time only while bound
    to a single core. Some selected numbers:

    lat_ctx -s 0 $i (the left most number is $i):

    15 3.09
    16 3.09
    17 3.11
    18 3.07
    19 2.99
    20 3.09
    21 3.05
    22 3.11
    23 3.05
    24 3.08
    25 3.06

    hackbench $i:

    80 11.720
    81 11.698
    82 11.888
    83 12.094
    84 12.232
    85 12.351
    86 12.512
    87 12.680
    88 12.736
    89 12.861
    90 13.103

    pipe-test (the left most number is the run #):

    1 8.85
    2 8.80
    3 8.84
    4 8.82
    5 8.82
    6 8.80
    7 8.82
    8 8.82
    9 8.85
    10 8.83

    Once again, graphs:
    http://www.healthcarelinen.com/misc/benchmarks/BOUND_PATCHED_lat_ctx_benchmark.png
    http://www.healthcarelinen.com/misc/benchmarks/BOUND_PATCHED_hackbench_benchmark.png
    http://www.healthcarelinen.com/misc/benchmarks/BOUND_PATCHED_pipe-test_benchmark.png

    I saw in your other email that you'd like for me to try with
    CONFIG_PREEMPT disabled. I should have a chance to try that very soon.

    Regards,
    Rob
    [unhandled content-type:application/x-bzip2][unhandled content-type:image/png][unhandled content-type:image/png][unhandled content-type:image/png][unhandled content-type:application/x-bzip2]
    \
     
     \ /
      Last update: 2007-09-18 03:47    [W:0.034 / U:61.424 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site