Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756101AbbGCQ3m (ORCPT ); Fri, 3 Jul 2015 12:29:42 -0400 Received: from mail-la0-f51.google.com ([209.85.215.51]:35001 "EHLO mail-la0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755970AbbGCQ3c (ORCPT ); Fri, 3 Jul 2015 12:29:32 -0400 MIME-Version: 1.0 In-Reply-To: References: <1a5858d079609a3e293123c9ee45de433a4e9c44.1435602481.git.luto@kernel.org> <20150702120932.GH4001@pd.tnic> <20150703063313.GA19561@gmail.com> From: Andy Lutomirski Date: Fri, 3 Jul 2015 09:29:11 -0700 Message-ID: Subject: Re: [PATCH v4 14/17] x86/asm/entry/64: Migrate error and interrupt exit work to C To: Ingo Molnar Cc: Borislav Petkov , Andy Lutomirski , X86 ML , "linux-kernel@vger.kernel.org" , =?UTF-8?B?RnLDqWTDqXJpYyBXZWlzYmVja2Vy?= , Rik van Riel , Oleg Nesterov , Denys Vlasenko , Kees Cook , Brian Gerst , Paul McKenney Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1287 Lines: 26 On Fri, Jul 3, 2015 at 9:27 AM, Andy Lutomirski wrote: > > I haven't benchmarked very carefully. IIRC syscall timing was > unaffected by this series. Exceptions ought to be unaffected unless > something very weird is going on with the trace cache or branch > predictor. IRQs will slow down by a couple cycles (I'm guessing 5, > since it's more or less the same change I benchmarked when I was > playing with the next pile of patches). One clarification: I bet that context tracking performance changes with these patches, but it sucked before and it'll suck afterwards regardless. I think that these patches are a good step in making it not suck, though -- they will allow us to only change ct state once on entry and once on exit, and we used to get it wrong. They also allow us to do context tracking with IRQs off, which Rik van Riel wanted to help his speedup project. So, in the long run, I expect a huge context tracking improvement, and these patches will help. By themselves, they won't do much. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/