From: Jaegeuk Hanse <jaegeuk.hanse@gmail.com>
To: Hugh Dickins <hughd@google.com>
Cc: Dave Jones <davej@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] tmpfs: fix shmem_getpage_gfp VM_BUG_ON
Date: Fri, 16 Nov 2012 08:40:14 +0800 [thread overview]
Message-ID: <50A58B6E.8090609@gmail.com> (raw)
In-Reply-To: <alpine.LNX.2.00.1211151126440.9273@eggly.anvils>
On 11/16/2012 03:56 AM, Hugh Dickins wrote:
> Offtopic...
>
> On Thu, 15 Nov 2012, Jaegeuk Hanse wrote:
>> Another question. Why the function shmem_fallocate which you add to kernel
>> need call shmem_getpage?
> Because shmem_getpage(_gfp) is where shmem's
> page lookup and allocation complexities are handled.
>
> I assume the question behind your question is: why does shmem actually
> allocate pages for its fallocate, instead of just reserving the space?
Yeah, this is what I want to know.
>
> I did play with just reserving the space, with more special entries in
> the radix_tree to note the reservations made. It should be doable for
> the vm_enough_memory and sbinfo->used_blocks reservations.
>
> What absolutely deterred me from taking that path was the mem_cgroup
> case: shmem and swap and memcg are not easy to get working right together,
> and nobody would thank me for complicating memcg just for shmem_fallocate.
>
> By allocating pages, the pre-existing memcg code just works; if we used
> reservations instead, we would have to track their memcg charges in some
> additional new way. I see no justification for that complication.
Oh, I see, thanks Hugh. :-)
> Hugh
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next prev parent reply other threads:[~2012-11-16 0:40 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-25 2:37 shmem_getpage_gfp VM_BUG_ON triggered. [3.7rc2] Dave Jones
2012-10-25 4:36 ` Hugh Dickins
2012-10-25 4:50 ` Ni zhan Chen
2012-10-25 6:59 ` Hugh Dickins
2012-10-25 9:53 ` Ni zhan Chen
2012-10-25 10:21 ` Ni zhan Chen
2012-10-25 21:27 ` Hugh Dickins
2012-10-26 1:48 ` Ni zhan Chen
2012-10-25 11:14 ` Dave Jones
2012-10-25 21:28 ` Hugh Dickins
2012-10-25 20:52 ` Johannes Weiner
2012-10-25 21:48 ` Hugh Dickins
2012-10-26 2:15 ` Ni zhan Chen
2012-11-01 19:10 ` Dave Jones
2012-11-01 23:03 ` Hugh Dickins
2012-11-01 23:20 ` Dave Jones
2012-11-01 23:48 ` Hugh Dickins
2012-11-02 1:43 ` Dave Jones
2012-11-02 23:26 ` Hugh Dickins
2012-11-06 1:32 ` [PATCH] tmpfs: fix shmem_getpage_gfp VM_BUG_ON Hugh Dickins
2012-11-06 13:54 ` Dave Jones
2012-11-06 23:48 ` Hugh Dickins
2012-11-07 22:38 ` Dave Jones
2012-11-14 1:36 ` [PATCH] tmpfs: fix shmem_getpage_gfp VM_BUG_ON fix Hugh Dickins
2012-11-14 3:07 ` [PATCH] tmpfs: fix shmem_getpage_gfp VM_BUG_ON Jaegeuk Hanse
2012-11-14 3:50 ` Hugh Dickins
2012-11-14 6:14 ` Dave Jones
2012-11-14 10:06 ` Hugh Dickins
2012-11-15 7:39 ` Jaegeuk Hanse
2012-11-15 19:56 ` Hugh Dickins
2012-11-16 0:40 ` Jaegeuk Hanse [this message]
2012-11-16 9:34 ` Jaegeuk Hanse
2012-11-17 4:48 ` Hugh Dickins
2012-11-18 0:57 ` Jaegeuk Hanse
2012-11-18 1:48 ` Jaegeuk Hanse
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