Hi Mel, We are glad to reprort much improved fileio.request_latency_max_ms on commit
commit 5d4cf996cf134e8ddb4f906b8197feb9267c2b77 Author: Mel Gorman <[email protected]> Date: Tue Dec 17 09:21:25 2013 +0000 sched: Assign correct scheduling domain to 'sd_llc' Commit 42eb088e (sched: Avoid NULL dereference on sd_busy) corrected a NULL dereference on sd_busy but the fix also altered what scheduling domain it used for the 'sd_llc' percpu variable. One impact of this is that a task selecting a runqueue may consider idle CPUs that are not cache siblings as candidates for running. Tasks are then running on CPUs that are not cache hot. This was found through bisection where ebizzy threads were not seeing equal performance and it looked like a scheduling fairness issue. This patch mitigates but does not completely fix the problem on all machines tested implying there may be an additional bug or a common root cause. Here are the average range of performance seen by individual ebizzy threads. It was tested on top of candidate patches related to x86 TLB range flushing. 4-core machine 3.13.0-rc3 3.13.0-rc3 vanilla fixsd-v3r3 Mean 1 0.00 ( 0.00%) 0.00 ( 0.00%) Mean 2 0.34 ( 0.00%) 0.10 ( 70.59%) Mean 3 1.29 ( 0.00%) 0.93 ( 27.91%) Mean 4 7.08 ( 0.00%) 0.77 ( 89.12%) Mean 5 193.54 ( 0.00%) 2.14 ( 98.89%) Mean 6 151.12 ( 0.00%) 2.06 ( 98.64%) Mean 7 115.38 ( 0.00%) 2.04 ( 98.23%) Mean 8 108.65 ( 0.00%) 1.92 ( 98.23%) 8-core machine Mean 1 0.00 ( 0.00%) 0.00 ( 0.00%) Mean 2 0.40 ( 0.00%) 0.21 ( 47.50%) Mean 3 23.73 ( 0.00%) 0.89 ( 96.25%) Mean 4 12.79 ( 0.00%) 1.04 ( 91.87%) Mean 5 13.08 ( 0.00%) 2.42 ( 81.50%) Mean 6 23.21 ( 0.00%) 69.46 (-199.27%) Mean 7 15.85 ( 0.00%) 101.72 (-541.77%) Mean 8 109.37 ( 0.00%) 19.13 ( 82.51%) Mean 12 124.84 ( 0.00%) 28.62 ( 77.07%) Mean 16 113.50 ( 0.00%) 24.16 ( 78.71%) It's eliminated for one machine and reduced for another. Signed-off-by: Mel Gorman <[email protected]> Signed-off-by: Peter Zijlstra <[email protected]> Cc: Alex Shi <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Fengguang Wu <[email protected]> Cc: H Peter Anvin <[email protected]> Cc: Linus Torvalds <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> 9dbdb155532395b 5d4cf996cf134e8ddb4f906b8 --------------- ------------------------- 1898 ~110% -84.0% 303 ~28% snb-drag/sysbench/fileio/600s-100%-1HDD-btrfs-64G-1024-seqwr-sync 1898 -84.0% 303 TOTAL fileio.request_latency_max_ms 9dbdb155532395b 5d4cf996cf134e8ddb4f906b8 --------------- ------------------------- 1712 ~ 3% +75.1% 2997 ~ 3% snb-drag/sysbench/fileio/600s-100%-1HDD-btrfs-64G-1024-seqwr-sync 1712 +75.1% 2997 TOTAL proc-vmstat.nr_tlb_remote_flush 9dbdb155532395b 5d4cf996cf134e8ddb4f906b8 --------------- ------------------------- 1774 ~ 3% +74.3% 3093 ~ 3% snb-drag/sysbench/fileio/600s-100%-1HDD-btrfs-64G-1024-seqwr-sync 1774 +74.3% 3093 TOTAL proc-vmstat.nr_tlb_remote_flush_received 9dbdb155532395b 5d4cf996cf134e8ddb4f906b8 --------------- ------------------------- 1707 ~ 2% +64.7% 2812 ~ 2% snb-drag/sysbench/fileio/600s-100%-1HDD-btrfs-64G-1024-seqwr-sync 1707 +64.7% 2812 TOTAL proc-vmstat.kswapd_high_wmark_hit_quickly 9dbdb155532395b 5d4cf996cf134e8ddb4f906b8 --------------- ------------------------- 13752 ~ 4% -71.5% 3916 ~ 1% snb-drag/sysbench/fileio/600s-100%-1HDD-btrfs-64G-1024-seqwr-sync 13752 -71.5% 3916 TOTAL time.involuntary_context_switches 9dbdb155532395b 5d4cf996cf134e8ddb4f906b8 --------------- ------------------------- 2797211 ~ 0% +22.8% 3434219 ~ 0% snb-drag/sysbench/fileio/600s-100%-1HDD-btrfs-64G-1024-seqwr-sync 2797211 +22.8% 3434219 TOTAL time.voluntary_context_switches 9dbdb155532395b 5d4cf996cf134e8ddb4f906b8 --------------- ------------------------- 9885 ~ 0% +22.4% 12102 ~ 0% snb-drag/sysbench/fileio/600s-100%-1HDD-btrfs-64G-1024-seqwr-sync 9885 +22.4% 12102 TOTAL vmstat.system.cs 9dbdb155532395b 5d4cf996cf134e8ddb4f906b8 --------------- ------------------------- 6 ~ 0% +16.7% 7 ~ 0% snb-drag/sysbench/fileio/600s-100%-1HDD-btrfs-64G-1024-seqwr-sync 6 +16.7% 7 TOTAL time.percent_of_cpu_this_job_got 9dbdb155532395b 5d4cf996cf134e8ddb4f906b8 --------------- ------------------------- 39.61 ~ 0% +14.9% 45.50 ~ 0% snb-drag/sysbench/fileio/600s-100%-1HDD-btrfs-64G-1024-seqwr-sync 39.61 +14.9% 45.50 TOTAL time.system_time Here are the visualized comparison of all GOOD/BAD commits during the bisect: fileio.request_latency_max_ms 8000 ++------------------------------------------------------------------+ | * | 7000 *+ * : * | 6000 ++ : * : : | | : : : : | 5000 ++ :: : :: : : | |: :: :: :: : : | 4000 ++ :: :: : : : : | |:: : :: : : : : | 3000 ++: : : : : : : : | 2000 ++: : : : : : : : | | : : : : : : : : | 1000 ++: : : :.* .*.* : : .*. : * | | * **.*.* * *.** *.*.** O*.*.**.** **.*.**.**.*.** *.**.* 0 O+OO-OO-O-OO-O-OO-OO-O-O----------O-OO-OO-O-OO-O-O--OO-O--O-O-OO----+ time.voluntary_context_switches 3.5e+06 ++---------------------------------------------------------------+ O OO OO OO OO OO O OO OO OO OO O OO OO O O O OO O OO OO | 3.4e+06 ++ O O O O O | | | 3.3e+06 ++ | 3.2e+06 ++ | | | 3.1e+06 ++ | | | 3e+06 ++ | 2.9e+06 ++ | | * *. *. | 2.8e+06 *+* .* + *.* .**. : * **.*.**. *. *.* .**. *.* .* .* .* .* | * * *.**.* * * * * *.* * * * * | 2.7e+06 ++---------------------------------------------------------------+ time.involuntary_context_switches 16000 ++-----------------------------------------------------------------+ | * | 14000 ++ :+ .**.* .**. * .* .* .**. .*.* *.*.* *. *.**.* *.**.* * *.* **. + * *.* * ** *.* *.* *.* | 12000 ++ * | | | 10000 ++ | | | 8000 ++ | | | 6000 ++ | | | 4000 O+OO OO O OO OO O OO OO O OO OO O OO OO OO O OO OO O OO OO O OO | | | 2000 ++-----------------------------------------------------------------+ vmstat.system.cs 12500 ++-----------------------------------------------------------------+ | O O O | 12000 O+OO OO O OO OO O OO OO O OO OO O OO OO OO O OO OO OO O O | | O | | | 11500 ++ | | | 11000 ++ | | | 10500 ++ | | | *. *. * *. *. .* | 10000 ++* .* + * + *.* + * **.*.**.**.** + *.**.*.**. *. .* .* .* | * * **.*.* * * * * * * | 9500 ++-----------------------------------------------------------------+ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
