On 09/02/2011 12:31 PM, Satoru Moriya wrote:
> On 09/01/2011 05:58 PM, Andrew Morton wrote:
>> On Thu, 1 Sep 2011 15:26:50 -0400
>> Rik van Riel <riel@xxxxxxxxxx> wrote:
> Anyway, now I'm testing this patch and will report a test result later.
Sorry for late reply. Here is my test result.
I ran some sample workloads and measure memory allocation latency
(latency of __alloc_page_nodemask()).
The test is like following:
- CPU: 1 socket, 4 core
- Memory: 4GB
- Background load:
$ dd if=/dev/zero of=/tmp/tmp1
$ dd if=/dev/zero of=/tmp/tmp2
$ dd if=/dev/zero of=/tmp/tmp3
- Main load:
$ mapped-file-stream 1 $((1024 * 1024 * 640)) --(*)
(*) This is made by Johannes Weiner
https://lkml.org/lkml/2010/8/30/226
It allocates/access 640MByte memory at a burst.
The result is follwoing:
| | extra |
| default | kbytes |
--------------------------------------------------------------
min_free_kbytes | 8113 | 8113 |
extra_free_kbytes | 0 | 640*1024 | (KB)
--------------------------------------------------------------
worst latency | 517.762 | 20.775 | (usec)
--------------------------------------------------------------
vmstat result | | |
nr_vmscan_write | 0 | 0 |
pgsteal_dma | 0 | 0 |
pgsteal_dma32 | 143667 | 144882 |
pgsteal_normal | 31486 | 27001 |
pgsteal_movable | 0 | 0 |
pgscan_kswapd_dma | 0 | 0 |
pgscan_kswapd_dma32 | 138617 | 156351 |
pgscan_kswapd_normal | 30593 | 27955 |
pgscan_kswapd_movable | 0 | 0 |
pgscan_direct_dma | 0 | 0 |
pgscan_direct_dma32 | 5050 | 0 |
pgscan_direct_normal | 896 | 0 |
pgscan_direct_movable | 0 | 0 |
kswapd_steal | 169207 | 171883 |
kswapd_inodesteal | 0 | 0 |
kswapd_low_wmark_hit_quickly | 43 | 45 |
kswapd_high_wmark_hit_quickly | 1 | 0 |
allocstall | 32 | 0 |
As you can see, in the default case there were 32 direct reclaim (allocstall)
and its worst latency was 517.762 usecs. This value may be larger if
a process would sleep or issue I/O in the direct reclaim path. OTOH,
ii the other case where I add extra free bytes, there were no direct
reclaim and its worst latency was 20.775 usecs.
In this test case, we can avoid direct reclaim and keep a latency low.
Tested-by: Satoru Moriya <satoru.moriya@xxxxxxx>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href