From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752059AbcHKX0g (ORCPT ); Thu, 11 Aug 2016 19:26:36 -0400 Received: from mail.efficios.com ([78.47.125.74]:46842 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750741AbcHKX0e (ORCPT ); Thu, 11 Aug 2016 19:26:34 -0400 Date: Thu, 11 Aug 2016 23:26:30 +0000 (UTC) From: Mathieu Desnoyers To: Dave Watson Cc: Andrew Morton , Russell King , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , linux-kernel , linux-api , Paul Turner , Andrew Hunter , Peter Zijlstra , Andy Lutomirski , Andi Kleen , Chris Lameter , Ben Maurer , rostedt , "Paul E. McKenney" , Josh Triplett , Linus Torvalds , Catalin Marinas , Will Deacon , Michael Kerrisk , Boqun Feng Message-ID: <374861479.8581.1470957990793.JavaMail.zimbra@efficios.com> In-Reply-To: References: <1469135662-31512-1-git-send-email-mathieu.desnoyers@efficios.com> <1469135662-31512-8-git-send-email-mathieu.desnoyers@efficios.com> <1590181502.79032.1469329777708.JavaMail.zimbra@efficios.com> Subject: Re: [RFC PATCH v7 7/7] Restartable sequences: self-tests MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [78.47.125.74] X-Mailer: Zimbra 8.7.0_GA_1659 (ZimbraWebClient - FF45 (Linux)/8.7.0_GA_1659) Thread-Topic: Restartable sequences: self-tests Thread-Index: AQHR45U4x18RQTQYYkqrz+QZ0tH6dqAmgBWtqVs2wOHWpixZPK3gbMn6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- On Jul 24, 2016, at 2:01 PM, Dave Watson davejwatson@fb.com wrote: >>> +static inline __attribute__((always_inline)) >>> +bool rseq_finish(struct rseq_lock *rlock, >>> + intptr_t *p, intptr_t to_write, >>> + struct rseq_state start_value) > >>> This ABI looks like it will work fine for our use case. I don't think it >>> has been mentioned yet, but we may still need multiple asm blocks >>> for differing numbers of writes. For example, an array-based freelist push: > >>> void push(void *obj) { >>> if (index < maxlen) { >>> freelist[index++] = obj; >>> } >>> } > >>> would be more efficiently implemented with a two-write rseq_finish: > >>> rseq_finish2(&freelist[index], obj, // first write >>> &index, index + 1, // second write >>> ...); > >> Would pairing one rseq_start with two rseq_finish do the trick >> there ? > > Yes, two rseq_finish works, as long as the extra rseq management overhead > is not substantial. I've added a commit implementing rseq_finish2() in my rseq volatile dev branch. You can fetch it at: https://github.com/compudj/linux-percpu-dev/tree/rseq-fallback I also have a separate test and benchmark tree in addition to the kernel selftests here: https://github.com/compudj/rseq-test I named the first write a "speculative" write, and the second write the "final" write. Would you like to extend the test cases to cover your intended use-case ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com