linux-kernel - Re: [PATCH 0 of 9] x86/smp function calls: convert x86 tlb flushes to use function calls [POST 2]

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: <20080819093130.GF28713@elte.hu>
Date:	Tue, 19 Aug 2008 11:31:30 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
	Andi Kleen <andi@...stfloor.org>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [PATCH 0 of 9] x86/smp function calls: convert x86 tlb flushes
	to use function calls [POST 2]

* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> Ingo Molnar wrote:
> > nice stuff!
> >
> > I suspect the extra cost might be worth it for two reasons: 1) we could 
> > optimize the cross-call implementation further
> 
> Unfortunately, I think the kmalloc fix for the RCU issue is going to 
> hurt quite a lot.

yeah :-(

Nick, is there any way to get rid of that kmalloc() in the async 
function call case? The whole premise of the smp_function_call() rewrite 
was that it's faster - and now it's measurably slower.

At least we could/should perhaps standardize/generalize all the 
'specific' IPI handlers into the smp_function_call() framework: if 
function address equals to a pre-cooked IPI entry point we could call 
that function without a kmalloc. As these are all hardwired, 
__builtin_is_constant_p() could come to the help as well. Hm?

	Ingo
--
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/