On 04/02/2013 11:40 AM, Lin Feng wrote:
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.
Feng, it's easy to understand now, thanks for your detailed explanation :)
Zhouping
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