From: Yang Shi <firstname.lastname@example.org>
To: Michal Hocko <email@example.com>, firstname.lastname@example.org
Cc: email@example.com, firstname.lastname@example.org, email@example.com,
Subject: Re: [RFC v2 PATCH] mm: shmem: make stat.st_blksize return huge page size if THP is on
Date: Mon, 23 Apr 2018 10:19:27 -0600 [thread overview]
Message-ID: <firstname.lastname@example.org> (raw)
On 4/23/18 9:04 AM, Michal Hocko wrote:
> On Sun 22-04-18 21:28:59, Yang Shi wrote:
>> On 4/22/18 6:47 PM, Michal Hocko wrote:
>>> will be used on the first aligned address even when the initial/last
>>> portion of the mapping is not THP aligned.
>> No, my test shows it is not. And, transhuge_vma_suitable() does check the
>> virtual address alignment. If it is not huge page size aligned, it will not
>> set PMD for huge page.
> It's been quite some time since I've looked at that code but I think you
> are wrong. It just doesn't make sense to make the THP decision on the
> VMA alignment much. Kirill, can you clarify please?
In the test, QEMU is trying to mmap a file (16GB in my configuration) +
a guard page. If the page size is 4KB, there not any pages are mapped by
PMD, but if the page size is 2MB (huge page aligned) we can see a lot
pages are mapped by PMD. The test result is showed in the commit log.
So, if your assumption is right, there must be something wrong in THP code.
> Please note that I have no objections to actually export the huge page
> size as the max block size but your changelog just doesn't make any
> sense to me.
next prev parent reply other threads:[~2018-04-23 16:19 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-20 16:33 [RFC v2 PATCH] mm: shmem: make stat.st_blksize return huge page size if THP is on Yang Shi
2018-04-23 0:47 ` Michal Hocko
2018-04-23 3:28 ` Yang Shi
2018-04-23 15:04 ` Michal Hocko
2018-04-23 16:19 ` Yang Shi [this message]
2018-04-24 3:41 ` Yang Shi
2018-04-24 12:43 ` Michal Hocko
2018-04-24 13:08 ` Yang Shi
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