From: Yang Shi <yang.shi@linux.alibaba.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: kirill.shutemov@linux.intel.com, hughd@google.com,
hch@infradead.org, viro@zeniv.linux.org.uk,
akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC v2 PATCH] mm: shmem: make stat.st_blksize return huge page size if THP is on
Date: Tue, 24 Apr 2018 07:08:36 -0600 [thread overview]
Message-ID: <eefa688b-3d0f-6c9b-628e-8b81394deca6@linux.alibaba.com> (raw)
In-Reply-To: <20180424124312.GZ17484@dhcp22.suse.cz>
On 4/24/18 6:43 AM, Michal Hocko wrote:
> On Mon 23-04-18 21:41:50, Yang Shi wrote:
>>
>> 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?
>> Thanks a lot Michal and Kirill to elaborate how tmpfs THP make pmd map.
>>
>> I did a quick test, THP will be PMD mapped as long as :
>> * hint address is huge page aligned if MAP_FIXED
>> Or
>> * offset is huge page aligned
>> And
>> * The size is big enough (>= huge page size)
>>
>> This test does verify what Kirill said. And, I dig into a little further
>> qemu code and did strace, qemu does try to mmap the file to non huge page
>> aligned address with MAP_FIXED.
> Does it make sense to contact Qemu developers and probably fix this?
Yes, I think so. We can submit a bug report to QEMU.
>
prev parent reply other threads:[~2018-04-24 13:08 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
2018-04-24 3:41 ` Yang Shi
2018-04-24 12:43 ` Michal Hocko
2018-04-24 13:08 ` Yang Shi [this message]
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