From: Yang Shi <yang.shi@linux.alibaba.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: willy@infradead.org, ldufour@linux.vnet.ibm.com,
kirill@shutemov.name, akpm@linux-foundation.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC v6 PATCH 2/2] mm: mmap: zap pages with read mmap_sem in munmap
Date: Mon, 6 Aug 2018 15:19:06 -0700 [thread overview]
Message-ID: <0cdff13a-2713-c5be-a33e-28c07e093bcc@linux.alibaba.com> (raw)
In-Reply-To: <20180806205232.GN10003@dhcp22.suse.cz>
On 8/6/18 1:52 PM, Michal Hocko wrote:
> On Mon 06-08-18 13:48:35, Yang Shi wrote:
>>
>> On 8/6/18 1:41 PM, Michal Hocko wrote:
>>> On Mon 06-08-18 09:46:30, Yang Shi wrote:
>>>> On 8/6/18 2:40 AM, Michal Hocko wrote:
>>>>> On Fri 03-08-18 14:01:58, Yang Shi wrote:
>>>>>> On 8/3/18 2:07 AM, Michal Hocko wrote:
>>>>>>> On Fri 27-07-18 02:10:14, Yang Shi wrote:
>>> [...]
>>>>>>>> If the vma has VM_LOCKED | VM_HUGETLB | VM_PFNMAP or uprobe, they are
>>>>>>>> considered as special mappings. They will be dealt with before zapping
>>>>>>>> pages with write mmap_sem held. Basically, just update vm_flags.
>>>>>>> Well, I think it would be safer to simply fallback to the current
>>>>>>> implementation with these mappings and deal with them on top. This would
>>>>>>> make potential issues easier to bisect and partial reverts as well.
>>>>>> Do you mean just call do_munmap()? It sounds ok. Although we may waste some
>>>>>> cycles to repeat what has done, it sounds not too bad since those special
>>>>>> mappings should be not very common.
>>>>> VM_HUGETLB is quite spread. Especially for DB workloads.
>>>> Wait a minute. In this way, it sounds we go back to my old implementation
>>>> with special handling for those mappings with write mmap_sem held, right?
>>> Yes, I would really start simple and add further enhacements on top.
>> If updating vm_flags with read lock is safe in this case, we don't have to
>> do this. The only reason for this special handling is about vm_flags update.
>
> Yes, maybe you are right that this is safe. I would still argue to have
> it in a separate patch for easier review, bisectability etc...
Sorry, I'm a little bit confused. Do you mean I should have the patch
*without* handling the special case (just like to assume it is safe to
update vm_flags with read lock), then have the other patch on top of it,
which simply calls do_munmap() to deal with the special cases?
>
next prev parent reply other threads:[~2018-08-06 22:19 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-26 18:10 [RFC v6 PATCH 0/2] mm: zap pages with read mmap_sem in munmap for large mapping Yang Shi
2018-07-26 18:10 ` [RFC v6 PATCH 1/2] mm: refactor do_munmap() to extract the common part Yang Shi
2018-08-03 8:53 ` Michal Hocko
2018-08-03 20:47 ` Yang Shi
2018-08-06 13:26 ` Michal Hocko
2018-08-06 16:53 ` Yang Shi
2018-08-07 14:59 ` Vlastimil Babka
2018-08-07 18:06 ` Yang Shi
2018-07-26 18:10 ` [RFC v6 PATCH 2/2] mm: mmap: zap pages with read mmap_sem in munmap Yang Shi
2018-07-26 18:34 ` Mika Penttilä
2018-07-26 19:03 ` Yang Shi
2018-07-27 8:15 ` Laurent Dufour
2018-07-27 16:18 ` Yang Shi
2018-08-03 9:07 ` Michal Hocko
2018-08-03 21:01 ` Yang Shi
2018-08-06 9:40 ` Michal Hocko
2018-08-06 16:46 ` Yang Shi
2018-08-06 20:41 ` Michal Hocko
2018-08-06 20:48 ` Yang Shi
2018-08-06 20:52 ` Michal Hocko
2018-08-06 22:19 ` Yang Shi [this message]
2018-08-07 5:45 ` Michal Hocko
2018-08-08 1:51 ` Yang Shi
2018-08-08 9:22 ` Vlastimil Babka
2018-08-08 17:19 ` Yang Shi
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