From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:48618)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <rth7680@gmail.com>) id 1ZesHN-0008KN-1K
	for qemu-devel@nongnu.org; Wed, 23 Sep 2015 18:12:45 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <rth7680@gmail.com>) id 1ZesHI-0006Cq-2N
	for qemu-devel@nongnu.org; Wed, 23 Sep 2015 18:12:44 -0400
Received: from mail-pa0-x236.google.com ([2607:f8b0:400e:c03::236]:35858)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <rth7680@gmail.com>) id 1ZesHH-0006Cb-Rp
	for qemu-devel@nongnu.org; Wed, 23 Sep 2015 18:12:39 -0400
Received: by pacgz1 with SMTP id gz1so2336512pac.3
	for <qemu-devel@nongnu.org>; Wed, 23 Sep 2015 15:12:38 -0700 (PDT)
Sender: Richard Henderson <rth7680@gmail.com>
References: <1442953507-4074-1-git-send-email-rth@twiddle.net>
	<1442953507-4074-25-git-send-email-rth@twiddle.net>
	<CAFEAcA90LirEsQjkRKBSdjW_4rx+YDe1LBNGS=bShtm7=hvi5A@mail.gmail.com>
	<560304E0.3020907@twiddle.net>
	<CAFEAcA9pO-gGd4_DwXB0sksL7kzZYV0CSxD9KCyYn13yiaN3Ng@mail.gmail.com>
From: Richard Henderson <rth@twiddle.net>
Message-ID: <560323D3.3080504@twiddle.net>
Date: Wed, 23 Sep 2015 15:12:35 -0700
MIME-Version: 1.0
In-Reply-To: <CAFEAcA9pO-gGd4_DwXB0sksL7kzZYV0CSxD9KCyYn13yiaN3Ng@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH v3 24/25] tcg: Allocate a guard page after
	code_gen_buffer
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>, QEMU Developers <qemu-devel@nongnu.org>, Aurelien Jarno <aurelien@aurel32.net>

On 09/23/2015 01:37 PM, Peter Maydell wrote:
> On 23 September 2015 at 13:00, Richard Henderson <rth@twiddle.net> wrote:
>> I've wondered about over-allocating on the mmap path, so that we can choose the
>> hugepage aligned subregion.  But as far as I can tell, my kernel doesn't
>> allocate hugepages at all, no matter what we do.  So it seems a little silly to
>> go so far out of the way to get an aligned buffer.
>
> This raises the converse question of "why are we bothering with
> MADV_HUGEPAGE at all?" :-)

I beg your pardon -- I was merely looking in the wrong place for the info. 
/proc/pid/smap does show that nearly all of the area is using huge pages:

Main memory:
7fc130000000-7fc1b0000000 rw-p 00000000 00:00 0
Size:            2097152 kB
Rss:               88064 kB
Pss:               88064 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:     88064 kB
Referenced:        88064 kB
Anonymous:         88064 kB
AnonHugePages:     88064 kB
Swap:                  0 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Locked:                0 kB

code_gen_buffer:
7fc1d76e6000-7fc1f76e6000 rwxp 00000000 00:00 0
Size:             524288 kB
Rss:               58472 kB
Pss:               58472 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:     58472 kB
Referenced:        58472 kB
Anonymous:         58472 kB
AnonHugePages:     57344 kB
Swap:                  0 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Locked:                0 kB


r~