From: Andrew Morton <akpm@linux-foundation.org>
To: Steven Truelove <steven.truelove@utoronto.ca>
Cc: wli@holomorphy.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] HUGETLBFS: Align memory request to multiple of huge page size to avoid underallocating.
Date: Mon, 27 Feb 2012 19:04:32 -0800 [thread overview]
Message-ID: <20120227190432.55d7399a.akpm@linux-foundation.org> (raw)
In-Reply-To: <4F4C4215.5020108@utoronto.ca>
On Mon, 27 Feb 2012 21:55:17 -0500 Steven Truelove <steven.truelove@utoronto.ca> wrote:
> > A few things...
> >
> > - sys_mmap_pgoff() does the rounding up prior to calling
> > hugetlb_file_setup(). ipc/shm.c:newseg() does not.
> >
> > We should be consistent here: do it in the caller or the callee,
> > not both (or neither!). I guess doing it in the callee would be
> > best.
> >
> > - The above code could/should have used ALIGN(). Or round_up(): the
> > difference presently escapes me, even though it was so obvious that
> > we left all these things undocumented.
> >
> > - What's the point in aligning the length if we don't also look at
> > the start address? If that isn't a multiple of huge_page_size(), we
> > will need an additional page.
> >
>
> Since mmap has an address to check and shmget does not, if the address
> is going to be checked it will need to be in the caller.
Or pass a value of 0 from shmget.
> If you like, I
> will leave the size check in hugetlb_file_setup() and remove the size
> check from mmap_pgoff, but replace it with a check of the address. That
> will centralize the common check (size of buffer), and let mmap_pgoff
> check the part that is unique to it. Patch shortly.
>
> Steven Truelove
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WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: Steven Truelove <steven.truelove@utoronto.ca>
Cc: wli@holomorphy.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] HUGETLBFS: Align memory request to multiple of huge page size to avoid underallocating.
Date: Mon, 27 Feb 2012 19:04:32 -0800 [thread overview]
Message-ID: <20120227190432.55d7399a.akpm@linux-foundation.org> (raw)
In-Reply-To: <4F4C4215.5020108@utoronto.ca>
On Mon, 27 Feb 2012 21:55:17 -0500 Steven Truelove <steven.truelove@utoronto.ca> wrote:
> > A few things...
> >
> > - sys_mmap_pgoff() does the rounding up prior to calling
> > hugetlb_file_setup(). ipc/shm.c:newseg() does not.
> >
> > We should be consistent here: do it in the caller or the callee,
> > not both (or neither!). I guess doing it in the callee would be
> > best.
> >
> > - The above code could/should have used ALIGN(). Or round_up(): the
> > difference presently escapes me, even though it was so obvious that
> > we left all these things undocumented.
> >
> > - What's the point in aligning the length if we don't also look at
> > the start address? If that isn't a multiple of huge_page_size(), we
> > will need an additional page.
> >
>
> Since mmap has an address to check and shmget does not, if the address
> is going to be checked it will need to be in the caller.
Or pass a value of 0 from shmget.
> If you like, I
> will leave the size check in hugetlb_file_setup() and remove the size
> check from mmap_pgoff, but replace it with a check of the address. That
> will centralize the common check (size of buffer), and let mmap_pgoff
> check the part that is unique to it. Patch shortly.
>
> Steven Truelove
next prev parent reply other threads:[~2012-02-28 3:03 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-27 14:09 [PATCH] HUGETLBFS: Align memory request to multiple of huge page size to avoid underallocating Steven Truelove
2012-02-27 23:42 ` Andrew Morton
2012-02-27 23:42 ` Andrew Morton
2012-02-28 2:55 ` Steven Truelove
2012-02-28 2:55 ` Steven Truelove
2012-02-28 3:04 ` Andrew Morton [this message]
2012-02-28 3:04 ` Andrew Morton
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