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Message-ID: <50B9E4C1.2050002@iskon.hr>
Date: Sat, 01 Dec 2012 12:06:41 +0100
From: Zlatko Calusic <zlatko.calusic@...on.hr>
To: Tejun Heo <tj@...nel.org>
CC: linux-kernel@...r.kernel.org
Subject: Re: High context switch rate, ksoftirqd's chewing cpu
On 30.11.2012 23:55, Tejun Heo wrote:
> Hello, again.
>
> Can you please try this patch? Thanks!
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 042d221..26368ef 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -1477,7 +1477,10 @@ bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
> } while (unlikely(ret == -EAGAIN));
>
> if (likely(ret >= 0)) {
> - __queue_delayed_work(cpu, wq, dwork, delay);
> + if (!delay)
> + __queue_work(cpu, wq, &dwork->work);
> + else
> + __queue_delayed_work(cpu, wq, dwork, delay);
> local_irq_restore(flags);
> }
>
>
I have good news. The patch fixes the regression!
To doublecheck and provide you additional data, I updated to the latest Linus
kernel (commit 7c17e48), recompiled (WITHOUT the patch), rebooted and this is
what vmstat 1 looks like:
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
1 0 0 2957924 43676 655840 0 0 868 460 1446 38112 1 1 75 23
0 0 0 2957436 43684 655672 0 0 8 1290 941 30743 1 2 96 1
0 0 0 2957416 43708 656120 0 0 300 501 755 23642 1 2 89 9
1 0 0 2957648 43740 656592 0 0 632 162 946 19837 1 3 81 17
0 0 0 2950104 43740 664660 0 0 8192 0 550 326 1 1 91 8
0 0 0 2950600 43772 664092 0 0 148 289 691 39594 0 1 90 9
0 0 0 2939580 43924 674612 0 0 5568 115 2424 38662 5 4 77 15
0 1 0 2944888 43932 669580 0 0 56 869 1095 20062 6 1 89 4
0 0 0 2945812 43936 670524 0 0 824 92 824 49790 0 2 93 5
1 0 0 2945724 44084 670656 0 0 348 91 650 26455 1 1 89 10
0 2 0 2945356 44380 670848 0 0 536 161 718 18824 1 2 76 22
0 0 0 2944432 44400 671216 0 0 156 534 684 16232 2 1 81 17
0 0 0 2943660 44412 671544 0 0 292 120 562 49618 1 3 87 10
0 0 0 2943740 44412 671520 0 0 0 9 393 7247 0 0 100 0
0 0 0 2943608 44420 671812 0 0 276 42 507 36329 1 1 96 3
0 0 0 2943704 44420 671996 0 0 176 0 405 269 0 0 100 0
0 0 0 2943548 44428 671964 0 0 0 238 534 14823 0 1 99 0
0 0 0 2943136 44444 672156 0 0 212 692 698 29321 1 2 86 11
Then I applied the patch and this is how vmstat 1 looks now (WITH the patch):
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
1 0 0 2736628 35160 897708 0 0 8 293 1172 2493 17 3 79 1
0 0 0 2737336 35172 897944 0 0 156 43 883 971 3 0 95 3
0 0 0 2736500 35212 898252 0 0 292 5564 1267 2168 14 2 79 5
0 0 0 2736056 35356 898864 0 0 596 51 1029 1344 2 3 90 6
0 0 0 2735732 35504 899284 0 0 516 82 1225 1495 2 2 85 11
0 1 0 2734052 35508 900324 0 0 512 91 1149 1225 2 2 93 4
0 0 0 2733980 35508 899820 0 0 0 17 918 1164 2 1 96 1
0 2 0 2733988 35812 899940 0 0 656 1764 1097 1549 3 2 79 17
0 0 0 2733792 35820 900348 0 0 40 76 1303 1299 2 3 83 13
0 0 0 2733888 35820 900344 0 0 0 17 914 1085 2 1 97 0
0 0 0 2733316 35952 900364 0 0 144 235 1062 1316 1 2 95 3
0 0 0 2733012 36092 900412 0 0 176 11 1112 1469 3 1 92 4
0 0 0 2732732 36236 900444 0 0 160 709 932 1022 2 1 93 5
1 0 0 2732128 36384 900400 0 0 156 8987 1491 2519 12 3 82 3
0 0 0 2732128 36384 900416 0 0 0 34 927 1376 5 2 93 0
0 0 0 2732044 36540 900788 0 0 444 82 963 1278 3 1 87 8
1 0 0 2732020 36680 900796 0 0 168 2 883 1041 1 2 94 2
0 0 0 2731228 36700 901456 0 0 324 196 882 1125 2 0 94 4
Observe the difference in the cs column!
I hope this gets in before 3.7.0. Good work Tejun!
Best regards,
--
Zlatko
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