On 09/10/2015 06:45 PM, Andrea Arcangeli wrote:
>Mysql (tokudb)
>https://dzone.com/articles/why-tokudb-hates-transparent
This seems a THP issue: unless the alternate malloc allocator starts
using MADV_NOHUGEPAGE, its memory loss would become extreme with the
split_huge_page pending changes from Kirill. There's little the kernel
can do about this, in fact Kirill's latest changes goes in the very
opposite direction of what's needed to reduce the memory footprint for
this MADV_DONTNEED 4kb case.
With current code however the best you can do is:
echo 0 >/sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_none
That will guarantee that khugepaged never increases the memory
footprint after a MADV_DONTNEED done by the alternate malloc
allocator. Just that will definitely stop to help with the
split_huge_page pending changes. You could consider testing that but
if the split_huge_page pending changes are merged, this tuning shall
disappear.
I don't think it's that pessimistic after Kirill's patchset?
MADV_DONTNEED should still result in unmaps, which results in
split_huge_pmd. Then the THP is put in a shrinker list and will be fully
split in response to memory pressure, see:
[PATCHv10 34/36] thp: introduce deferred_split_huge_page()
--
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/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>