Messages in this thread | | | Date | Tue, 02 Apr 2013 11:40:25 +0800 | From | Lin Feng <> | Subject | Re: THP: AnonHugePages in /proc/[pid]/smaps is correct or not? |
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Hi Zhouping,
On 04/02/2013 11:09 AM, Zhouping Liu wrote: > I don't understand clearly the last sentence 'you'll probably only get 100% hugepages only 1/512th of the time.' > could you please explain more details about 'only 1/512th of the time'?
IIUC, thp size is 2M so it may be comprised of 512 normal page(size 4k). Since your test code is not 2M aligned(not using posix_memalign()) so the start address of the mapped vma will be random, such as 2M*i+4k*1, 2M*i+4k*2...2M*i+k4*511, there is 512 possibilities.
The only chance you get thp happens when the first map just starts at 2M*i, and the consequent maps also benefit from this.
-------- snip -------- > > so, again, if I understand correctly, thp should tune the naturally aligned maps, such as generated by mmap()/malloc(), > make such maps 'hugepagesize' aligned if the maps or vma is equal and greater than 'hugepagesize', doesn't it?
We may gain performance improving from this.
thanks, linfeng
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