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List:       linux-mm
Subject:    Re: Kernel 2.6.8.1: swap storm of death - nr_requests > 1024 on swap partition
From:       Karl Vogel <karl.vogel () seagha ! com>
Date:       2004-08-30 23:02:06
Message-ID: 200408310102.06510.karl.vogel () seagha ! com
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On Monday 30 August 2004 22:33, Marcelo Tosatti wrote:
> Can you please try the following - it limits the number of in-flight
> writeback pages to 25% of total RAM at the VM level.
>
> Does wonders for me with 8192 nr_requests. The hogs finish _much_ faster
> and and interactivity feels much better.
>
> With nr_requests=128, this limit is not reached (probably never), but with
> 8192, it certainly does.
>
> --- a/mm/vmscan.c	2004-08-30 17:50:25.000000000 -0300
> +++ b/mm/vmscan.c	2004-08-30 18:34:54.666423368 -0300
> @@ -247,6 +247,12 @@
>
>  static int may_write_to_queue(struct backing_dev_info *bdi)
>  {
> +	int nr_writeback = read_page_state(nr_writeback);
> +
> +	if (nr_writeback > (totalram_pages * 25 / 100)) {
> +		blk_congestion_wait(WRITE, HZ/5);
> +		return 0;
> +	}
>  	if (current_is_kswapd())
>  		return 1;
>  	if (current_is_pdflush())	/* This is unlikely, but why not... */

This fixes the OOM for me.. I can do some more testing if needed tomorrow..

[kvo@localhost sources]$ cat /proc/meminfo
MemTotal:       515728 kB
MemFree:        445084 kB
Buffers:          9492 kB
Cached:          33268 kB
SwapCached:          0 kB
Active:          19748 kB
Inactive:        28716 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:       515728 kB
LowFree:        445084 kB
SwapTotal:     1044216 kB
SwapFree:      1044216 kB
Dirty:              84 kB
Writeback:           0 kB
Mapped:           8960 kB
Slab:            17284 kB
Committed_AS:     9544 kB
PageTables:        548 kB
VmallocTotal:   516020 kB
VmallocUsed:      2372 kB
VmallocChunk:   512624 kB
HugePages_Total:     0
HugePages_Free:      0
Hugepagesize:     4096 kB
[kvo@localhost sources]$ date;./expunge 1024;date;time cat /proc/meminfo;date
Tue Aug 31 00:51:20 CEST 2004
Tue Aug 31 00:51:55 CEST 2004
MemTotal:       515728 kB
MemFree:        381036 kB
Buffers:           272 kB
Cached:           2844 kB
SwapCached:     120572 kB
Active:           2036 kB
Inactive:       121868 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:       515728 kB
LowFree:        381036 kB
SwapTotal:     1044216 kB
SwapFree:       919020 kB
Dirty:               0 kB
Writeback:           0 kB
Mapped:           1420 kB
Slab:             5932 kB
Committed_AS:     9764 kB
PageTables:        572 kB
VmallocTotal:   516020 kB
VmallocUsed:      2372 kB
VmallocChunk:   512624 kB
HugePages_Total:     0
HugePages_Free:      0
Hugepagesize:     4096 kB

real	0m0.071s
user	0m0.000s
sys	0m0.000s
Tue Aug 31 00:51:55 CEST 2004
[kvo@localhost sources]$ date;./expunge 1024;date;time cat /proc/meminfo;date
Tue Aug 31 00:52:41 CEST 2004
Tue Aug 31 00:53:16 CEST 2004
MemTotal:       515728 kB
MemFree:        383832 kB
Buffers:           220 kB
Cached:           2792 kB
SwapCached:     117196 kB
Active:           1944 kB
Inactive:       118652 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:       515728 kB
LowFree:        383832 kB
SwapTotal:     1044216 kB
SwapFree:       922316 kB
Dirty:               0 kB
Writeback:       16432 kB
Mapped:           1484 kB
Slab:             6328 kB
Committed_AS:     9768 kB
PageTables:        572 kB
VmallocTotal:   516020 kB
VmallocUsed:      2372 kB
VmallocChunk:   512624 kB
HugePages_Total:     0
HugePages_Free:      0
Hugepagesize:     4096 kB

real	0m0.328s
user	0m0.000s
sys	0m0.001s
Tue Aug 31 00:53:16 CEST 2004
[kvo@localhost sources]$ exit
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