Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758767AbYGORug (ORCPT ); Tue, 15 Jul 2008 13:50:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754531AbYGORu2 (ORCPT ); Tue, 15 Jul 2008 13:50:28 -0400 Received: from tomts36.bellnexxia.net ([209.226.175.93]:61297 "EHLO tomts36-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754142AbYGORu1 (ORCPT ); Tue, 15 Jul 2008 13:50:27 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AvIEAFh9fEhMRKxB/2dsb2JhbACBWq13 Date: Tue, 15 Jul 2008 13:50:25 -0400 From: Mathieu Desnoyers To: Peter Zijlstra Cc: akpm@linux-foundation.org, Ingo Molnar , linux-kernel@vger.kernel.org, Masami Hiramatsu , "Frank Ch. Eigler" , Hideo AOKI , Takashi Nishiie , Steven Rostedt , Alexander Viro , Eduard - Gabriel Munteanu , Paul E McKenney Subject: Re: [patch 01/15] Kernel Tracepoints Message-ID: <20080715175025.GA1936@Krystal> References: <20080709145929.352201601@polymtl.ca> <20080709150043.693920317@polymtl.ca> <1216108237.12595.122.camel@twins> <20080715132543.GB20037@Krystal> <1216130356.12595.184.camel@twins> <20080715142710.GC20037@Krystal> <1216132928.12595.201.camel@twins> <20080715152224.GE20037@Krystal> <1216135902.12595.214.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <1216135902.12595.214.camel@twins> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 13:43:53 up 40 days, 22:24, 4 users, load average: 0.87, 1.61, 1.24 User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3091 Lines: 69 * Peter Zijlstra (peterz@infradead.org) wrote: > > > Anyway, does this still generate better code? > > > > > > > On x86_64 : > > > > 820: bf 01 00 00 00 mov $0x1,%edi > > 825: e8 00 00 00 00 callq 82a > > 82a: 48 8b 1d 00 00 00 00 mov 0x0(%rip),%rbx # 831 > > 831: 48 85 db test %rbx,%rbx > > 834: 75 21 jne 857 > > 836: eb 27 jmp 85f > > 838: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1) > > 83f: 00 > > 840: 48 8b 95 68 ff ff ff mov -0x98(%rbp),%rdx > > 847: 48 8b b5 60 ff ff ff mov -0xa0(%rbp),%rsi > > 84e: 4c 89 e7 mov %r12,%rdi > > 851: 48 83 c3 08 add $0x8,%rbx > > 855: ff d0 callq *%rax > > 857: 48 8b 03 mov (%rbx),%rax > > 85a: 48 85 c0 test %rax,%rax > > 85d: 75 e1 jne 840 > > 85f: bf 01 00 00 00 mov $0x1,%edi > > 864: > > > > for 68 bytes. > > > > My original implementation was 77 bytes, so yes, we have a win. > > Ah, good good ! :-) > For the same number of instruction bytes, here is yet another improvement. I removed the it_func[0] NULL test case, which is impossible. We never have an empty array. If the array is empty, the array pointer is set to NULL and the array is eventually freed when a quiescent state is reached. /* * it_func[0] is never NULL because there is at least one element in the array * when the array itself is non NULL. */ #define __DO_TRACE(tp, proto, args) \ do { \ void **it_func; \ \ preempt_disable(); \ it_func = rcu_dereference((tp)->funcs); \ if (it_func) { \ do { \ ((void(*)(proto))(*it_func))(args); \ } while (*(++it_func)); \ } \ preempt_enable(); \ } while (0) P.S.: I'll change the preempt_enable/disable for rcu locks when I port this patchset to linux.next. I temporarily keep the preempt disable/enable statements. Mathieu -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- 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/