From: Roland Dreier <rdreier@cisco.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
Arjan van de Ven <arjan@infradead.org>,
Ingo Molnar <mingo@elte.hu>,
Siarhei Liakh <sliakh.lkml@gmail.com>,
linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org,
James Morris <jmorris@namei.org>,
Andrew Morton <akpm@linux-foundation.org>, Andi Kleen <ak@muc.de>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
linux-cris-kernel@axis.com
Subject: Re: [PATCH v5] RO/NX protection for loadable kernel modules
Date: Mon, 13 Jul 2009 09:59:04 -0700 [thread overview]
Message-ID: <adaskh0v7s7.fsf@cisco.com> (raw)
In-Reply-To: <87skh29ru2.fsf@basil.nowhere.org> (Andi Kleen's message of "Sun, 12 Jul 2009 11:24:37 +0200")
> > (I like the idea of trying kmalloc and falling back, simply because it reduces
> > TLB pressure,
>
> I implemented this for 32bit in 2.4, but I always had second thoughts
> if that was really reducing TLB pressure.
Certainly for non-x86 it can be very worthwhile. A long time ago I
worked on an embedded product that used PowerPC 440, which has only 64
(software-loaded) TLB entries. On PPC 440, Linux has a pinned TLB entry
for the kernel mapping, and modifying how the module loader allocated
space to load modules into that mapping vs. one that had dynamic TLB
entries was worth a factor of 2 in performance -- ie the TLB miss
handling for .text was literally taking half the CPU time of the module
code!
- R.
next prev parent reply other threads:[~2009-07-13 16:59 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-08 23:10 [PATCH v5] RO/NX protection for loadable kernel modules Siarhei Liakh
[not found] ` <20090710112403.GC3760@elte.hu>
[not found] ` <200907111537.03191.rusty@rustcorp.com.au>
2009-07-11 7:30 ` Ingo Molnar
2009-07-11 11:22 ` Rusty Russell
2009-07-11 8:51 ` Rusty Russell
2009-07-11 15:49 ` Arjan van de Ven
2009-07-12 4:40 ` Rusty Russell
2009-07-12 4:45 ` H. Peter Anvin
2009-07-12 7:45 ` Arjan van de Ven
2009-07-12 9:25 ` Andi Kleen
2009-07-12 9:58 ` Rusty Russell
2009-07-12 15:32 ` Arjan van de Ven
2009-07-12 17:33 ` Greg KH
2009-07-12 21:58 ` Arjan van de Ven
2009-07-12 22:14 ` Greg KH
2009-07-13 9:02 ` Andi Kleen
2009-07-12 23:21 ` Rusty Russell
2009-07-13 3:11 ` Arjan van de Ven
2009-07-12 9:24 ` Andi Kleen
2009-07-13 16:59 ` Roland Dreier [this message]
2009-07-13 10:59 ` Jesper Nilsson
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