linux-kernel - Re: [RFC 2/4] Have __free_pages_memory() free in larger chunks.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20130723153257.GK715@cmpxchg.org>
Date:	Tue, 23 Jul 2013 11:32:57 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Sam Ben <sam.bennn@...il.com>
Cc:	Robin Holt <holt@....com>, "H. Peter Anvin" <hpa@...or.com>,
	Ingo Molnar <mingo@...nel.org>, Nate Zimmer <nzimmer@....com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>, Rob Landley <rob@...dley.net>,
	Mike Travis <travis@....com>,
	Daniel J Blueman <daniel@...ascale-asia.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Yinghai Lu <yinghai@...nel.org>, Mel Gorman <mgorman@...e.de>
Subject: Re: [RFC 2/4] Have __free_pages_memory() free in larger chunks.

On Tue, Jul 16, 2013 at 09:02:53PM +0800, Sam Ben wrote:
> Hi Robin,
> On 07/12/2013 10:03 AM, Robin Holt wrote:
> >Currently, when free_all_bootmem() calls __free_pages_memory(), the
> >number of contiguous pages that __free_pages_memory() passes to the
> >buddy allocator is limited to BITS_PER_LONG.  In order to be able to
> 
> I fail to understand this. Why the original page number is BITS_PER_LONG?

The mm/bootmem.c implementation uses a bitmap to keep track of
free/reserved pages.  It walks that bitmap in BITS_PER_LONG steps
because it is the biggest chunk that is still trivial and cheap to
check if all pages are free in it (chunk == ~0UL).

nobootmem.c was written based on the bootmem.c interface, so it was
probably adapted to keep things similar between the two, short of a
pressing reason not to.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/