From: Vlastimil Babka <vbabka@suse.cz>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: linux-mips@linux-mips.org, Rich Felker <dalias@libc.org>,
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"David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH 2/4] mm: speed up mremap by 500x on large regions (v2)
Date: Wed, 17 Oct 2018 09:38:16 +0200 [thread overview]
Message-ID: <80a7d851-51ca-2d81-1273-393d4f701bc4@suse.cz> (raw)
In-Reply-To: <20181016194313.GA247930@joelaf.mtv.corp.google.com>
On 10/16/18 9:43 PM, Joel Fernandes wrote:
> On Tue, Oct 16, 2018 at 01:29:52PM +0200, Vlastimil Babka wrote:
>> On 10/16/18 12:33 AM, Joel Fernandes wrote:
>>> On Mon, Oct 15, 2018 at 02:42:09AM -0700, Christoph Hellwig wrote:
>>>> On Fri, Oct 12, 2018 at 06:31:58PM -0700, Joel Fernandes (Google) wrote:
>>>>> Android needs to mremap large regions of memory during memory management
>>>>> related operations.
>>>>
>>>> Just curious: why?
>>>
>>> In Android we have a requirement of moving a large (up to a GB now, but may
>>> grow bigger in future) memory range from one location to another.
>>
>> I think Christoph's "why?" was about the requirement, not why it hurts
>> applications. I admit I'm now also curious :)
>
> This issue was discovered when we wanted to be able to move the physical
> pages of a memory range to another location quickly so that, after the
> application threads are resumed, UFFDIO_REGISTER_MODE_MISSING userfaultfd
> faults can be received on the original memory range. The actual operations
> performed on the memory range are beyond the scope of this discussion. The
> user threads continue to refer to the old address which will now fault. The
> reason we want retain the old memory range and receives faults there is to
> avoid the need to fix the addresses all over the address space of the threads
> after we finish with performing operations on them in the fault handlers, so
> we mremap it and receive faults at the old addresses.
>
> Does that answer your question?
Yes, interesting, thanks!
Vlastimil
> thanks,
>
> - Joel
>
next prev parent reply other threads:[~2018-10-17 10:02 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-13 1:31 [PATCH 0/4] Add support for fast mremap Joel Fernandes (Google)
2018-10-13 1:31 ` [PATCH 1/4] treewide: remove unused address argument from pte_alloc functions (v2) Joel Fernandes (Google)
2018-10-24 8:37 ` Peter Zijlstra
2018-10-25 2:21 ` Joel Fernandes
2018-10-26 8:52 ` Peter Zijlstra
2018-10-25 10:47 ` Kirill A. Shutemov
2018-10-26 8:50 ` Peter Zijlstra
2018-10-13 1:31 ` [PATCH 2/4] mm: speed up mremap by 500x on large regions (v2) Joel Fernandes (Google)
2018-10-15 9:42 ` Christoph Hellwig
2018-10-15 22:33 ` Joel Fernandes
2018-10-16 11:29 ` Vlastimil Babka
2018-10-16 19:43 ` Joel Fernandes
2018-10-17 7:38 ` Vlastimil Babka [this message]
2018-10-24 10:12 ` Kirill A. Shutemov
2018-10-24 11:57 ` Balbir Singh
2018-10-24 12:57 ` Kirill A. Shutemov
2018-10-25 2:09 ` Joel Fernandes
2018-10-25 10:19 ` Kirill A. Shutemov
2018-10-26 21:11 ` Joel Fernandes
2018-10-29 10:28 ` Will Deacon
2018-10-25 2:13 ` Joel Fernandes
2018-10-27 10:21 ` Balbir Singh
2018-10-27 19:39 ` Joel Fernandes
2018-10-28 22:40 ` Balbir Singh
2018-10-13 1:31 ` [PATCH 3/4] arm64: select HAVE_MOVE_PMD for faster mremap (v1) Joel Fernandes (Google)
2018-10-13 1:32 ` [PATCH 4/4] x86: " Joel Fernandes (Google)
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