[...]
[missing patch #3]
I tried to get a similar patch working for swap out in shrink_page_list. And
it worked in functional terms, but the additional mergin was negligible.
I think we have already done it.
Look at shrink_mem_cgroup_zone which ends up calling shrink_page_list so we already have applied
I/O plugging.
I saw that code and it is part of the kernel I used to test my patches.
But despite that code and my additional experiments of plug/unplug in
shrink_page_list the effective I/O size of swap write stays at almost 4k.
Thereby so far I can tell you that the plugs in shrink_page_list and
shrink_mem_cgroup_zone aren't sufficient - at least for my case.
You saw the blocktrace summaries in my first mail, an excerpt of a write
submission stream looks like that:
94,4 10 465 0.023520923 116 A W 28868648 + 8 <- (94,5)
28868456
94,5 10 466 0.023521173 116 Q W 28868648 + 8 [kswapd0]
94,5 10 467 0.023522048 116 G W 28868648 + 8 [kswapd0]
94,5 10 468 0.023522235 116 P N [kswapd0]
94,5 10 469 0.023759892 116 I W 28868648 + 8 ( 237844)
[kswapd0]
94,5 10 470 0.023760079 116 U N [kswapd0] 1
94,5 10 471 0.023760360 116 D W 28868648 + 8 ( 468)
[kswapd0]
94,4 10 472 0.023891235 116 A W 28868656 + 8 <- (94,5)
28868464
94,5 10 473 0.023891454 116 Q W 28868656 + 8 [kswapd0]
94,5 10 474 0.023892110 116 G W 28868656 + 8 [kswapd0]
94,5 10 475 0.023944610 116 I W 28868656 + 8 ( 52500)
[kswapd0]
94,5 10 476 0.023944735 116 U N [kswapd0] 1
94,5 10 477 0.023944892 116 D W 28868656 + 8 ( 282)
[kswapd0]
94,5 16 19 0.024023192 16033 C W 28868648 + 8 ( 262832) [0]
94,5 24 37 0.024196752 14526 C W 28868656 + 8 ( 251860) [0]
[...]
But we can split this discussion from my other two patches and I would
be happy to provide my test environment for further tests if there are
new suggestions/patches/...
Maybe the cond_resched triggers much mor often than I expected, I'm open for
suggestions regarding improving the pagout I/O sizes as well.
We could enhance write out by batch like ext4_bio_write_page.
Do you mean the changes brought by "bd2d0210 ext4: use bio layer instead
of buffer layer in mpage_da_submit_io" ?
--
Grüsse / regards, Christian Ehrhardt
IBM Linux Technology Center, System z Linux Performance
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