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: <1303940249.9516.366.camel@nimitz>
Date:	Wed, 27 Apr 2011 14:37:29 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Timur Tabi <timur@...escale.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andi Kleen <andi@...stfloor.org>, Mel Gorman <mel@....ul.ie>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Nazarewicz <mina86@...a86.com>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH 2/3] make new alloc_pages_exact()

On Wed, 2011-04-27 at 16:30 -0500, Timur Tabi wrote:
> Dave Hansen wrote:
> > What I really wanted in the end was a highmem-capable
> > alloc_pages_exact(), so here it is.  This function can be used to
> > allocate unmapped (like highmem) non-power-of-two-sized areas of
> > memory.  This is in constast to get_free_pages_exact() which can only
> > allocate from lowmem.
> 
> Is there an easy way to verify that alloc_pages_exact(5MB) really does allocate
> only 5MB and not 8MB?

I'm not sure why you're asking.  How do we know that the _normal_
allocator only gives us 4k when we ask for 4k?  Well, that's just how it
works.  If alloc_pages_exact() returns success, you know it's got the
amount of memory that you asked for, and only that plus a bit of masking
for page alignment.

Have you seen alloc_pages_exact() behaving in some other way?

> Is there some kind of function that returns the amount of
> unallocated memory, so I can do a diff?

Nope.  Even if there was, it would be worthless.  Calls to this might
also cause the system to swap or reclaim memory, so you might end up
with the same amount of free memory before and after the call.  

-- Dave

--
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/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ