* why not add __GFP_HIGHMEM directly in alloc_migrate_target()?
@ 2016-07-12 13:16 Xishi Qiu
0 siblings, 0 replies; only message in thread
From: Xishi Qiu @ 2016-07-12 13:16 UTC (permalink / raw)
To: Linux MM, LKML
alloc_migrate_target() is called from migrate_pages(),
so the page is always from user space, so why not add
__GFP_HIGHMEM directly, instead of the following code.
if (PageHighMem(page)) // it always return false in x86_64
gfp_mask |= __GFP_HIGHMEM;
Another question, when we do migration, why should split THP
first?
e.g. 2M(512*4kb) should flush 512 times TLB, and 2M(2M*1) only need one.
I find flush TLB takes a lot of time, especially multithreaded app.
Thanks,
Xishi Qiu
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