On 05/22/2015 05:33 AM, Mel Gorman wrote:
On Fri, May 22, 2015 at 02:30:01PM +0800, Daniel J Blueman wrote:
On Thu, May 14, 2015 at 6:03 PM, Daniel J Blueman
<daniel@xxxxxxxxxxxxx> wrote:
On Thu, May 14, 2015 at 12:31 AM, Mel Gorman<mgorman@xxxxxxx> wrote:
On Wed, May 13, 2015 at 10:53:33AM -0500, nzimmer wrote:
I am just noticed a hang on my largest box.
I can only reproduce with large core counts, if I turn down the
number of cpus it doesn't have an issue.
Odd. The number of core counts should make little a difference
as only
one CPU per node should be in use. Does sysrq+t give any
indication how
or where it is hanging?
I was seeing the same behaviour of 1000ms increasing to 5500ms
[1]; this suggests either lock contention or O(n) behaviour.
Nathan, can you check with this ordering of patches from Andrew's
cache [2]? I was getting hanging until I a found them all.
I'll follow up with timing data.
7TB over 216 NUMA nodes, 1728 cores, from kernel 4.0.4 load to login:
1. 2086s with patches 01-19 [1]
2. 2026s adding "Take into account that large system caches scale
linearly with memory", which has:
min(2UL<< (30 - PAGE_SHIFT), (pgdat->node_spanned_pages>> 3));
3. 2442s fixing to:
max(2UL<< (30 - PAGE_SHIFT), (pgdat->node_spanned_pages>> 3));
4. 2064s adjusting minimum and shift to:
max(512UL<< (20 - PAGE_SHIFT), (pgdat->node_spanned_pages>> 8));
5. 1934s adjusting minimum and shift to:
max(128UL<< (20 - PAGE_SHIFT), (pgdat->node_spanned_pages>> 8));
6. 930s #5 with the non-temporal PMD init patch I had earlier
proposed (I'll pursue separately)
The scaling patch isn't in -mm.
That patch was superceded by "mm: meminit: finish
initialisation of struct pages before basic setup" and
"mm-meminit-finish-initialisation-of-struct-pages-before-basic-setup-fix"
so that's ok.
FWIW, I think you should still go ahead with the non-temporal patches because
there is potential benefit there other than the initialisation. If there
was an arch-optional implementation of a non-termporal clear then it would
also be worth considering if __GFP_ZERO should use non-temporal stores.
At a greater stretch it would be worth considering if kswapd freeing should
zero pages to avoid a zero on the allocation side in the general case as
it would be more generally useful and a stepping stone towards what the
series "Sanitizing freed pages" attempts.
I think the non-temporal patch benefits mainly AMD systems. I have tried
the patch on both DragonHawk and it actually made it boot up a little
bit slower. I think the Intel optimized "rep stosb" instruction (used in
memset) is performing well. I had done similar test on zero page code
and the performance gain was non-conclusive.
Cheers,
Longman
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