From: Matt Mackall <mpm@selenic.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Jack Steiner <steiner@sgi.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Stephen Hemminger <shemminger@vyatta.com>
Subject: Re: [PATCH v2] - Randomize node rotor used in cpuset_mem_spread_node()
Date: Wed, 28 Apr 2010 18:28:05 -0500 [thread overview]
Message-ID: <1272497285.21962.1110.camel@calx> (raw)
In-Reply-To: <20100428161244.5d351395.akpm@linux-foundation.org>
On Wed, 2010-04-28 at 16:12 -0700, Andrew Morton wrote:
> On Wed, 28 Apr 2010 18:04:06 -0500
> Matt Mackall <mpm@selenic.com> wrote:
>
> > > I suspect random32() would suffice here. It avoids depleting the
> > > entropy pool altogether.
> >
> > I wouldn't worry about that. get_random_int() touches the urandom pool,
> > which will always leave entropy around. Also, Ted and I decided over a
> > year ago that we should drop the whole entropy accounting framework,
> > which I'll get around to some rainy weekend.
>
> hm, so why does random32() exist? Speed?
Yep. There are lots of RNG uses that aren't security sensitive and this
is one: the kernel won't be DoSed by an attacker that gets all pages
preferentially allocated on one node. Performance will suffer, but it's
reasonably bounded.
One of my goals is to call these sorts of trade-offs out in the API, ie:
get_fast_random_u32()
get_fast_random_bytes()
get_secure_random_u32()
get_secure_random_bytes()
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next prev parent reply other threads:[~2010-04-28 23:28 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-28 13:12 [PATCH] - Randomize node rotor used in cpuset_mem_spread_node() Jack Steiner
2010-04-28 15:04 ` [PATCH v2] " Jack Steiner
2010-04-28 22:40 ` Andrew Morton
2010-04-28 23:04 ` Matt Mackall
2010-04-28 23:12 ` Andrew Morton
2010-04-28 23:22 ` Stephen Hemminger
2010-04-28 23:28 ` Matt Mackall [this message]
2010-04-29 3:57 ` Robin Holt
2010-04-29 20:08 ` Jack Steiner
2010-04-29 20:09 ` [PATCH v3] " Jack Steiner
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