From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gnu.wildebeest.org (gnu.wildebeest.org [45.83.234.184]) by sourceware.org (Postfix) with ESMTPS id 002B83858C2F for ; Mon, 15 Aug 2022 22:27:41 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 002B83858C2F Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=klomp.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=klomp.org Received: from reform (unknown [178.226.219.83]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by gnu.wildebeest.org (Postfix) with ESMTPSA id 1750C300070C; Tue, 16 Aug 2022 00:27:39 +0200 (CEST) Received: by reform (Postfix, from userid 1000) id C83F82E80816; Tue, 16 Aug 2022 00:27:37 +0200 (CEST) Date: Tue, 16 Aug 2022 00:27:37 +0200 From: Mark Wielaard To: Wilco Dijkstra Cc: 'GNU C Library' , Thomas Fitzsimmons Subject: Re: [PATCH] Improve performance of IO locks Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, JMQ_SPF_NEUTRAL, KAM_DMARC_STATUS, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 15 Aug 2022 22:27:44 -0000 Hi, On Mon, Aug 01, 2022 at 11:06:07AM +0000, Wilco Dijkstra via Libc-alpha wrote: > Improve performance of recursive IO locks by adding a fast path for > the single-threaded case. To reduce the number of memory accesses for > locking/unlocking, only increment the recursion counter if the lock > is already taken. > > On Neoverse V1, a microbenchmark with many small freads improved by > 2.9 times. Multithreaded performance improved by 2%. Strangely this seems to have broken the glibc-debian-ppc64 buildbot: https://builder.sourceware.org/buildbot/#/builders/glibc-debian-ppc64 I don't see how this commit can cause a failure just on debian-ppc64 (all other distro/arches are fine). And the corresponding bunsen test results don't really show why. https://builder.sourceware.org/testrun/498f51f327afdd7030516455b709a31a0038b432 Most of the .out files are empty, but some indicate an segmentation fault. Comparing to the build before only shows test result diffs, no configuration differences. https://builder.sourceware.org/testrun-diffs?commitish=498f51f327afdd7030516455b709a31a0038b432&commitish=58fd9d63b078b6bbfdba45135c4021038f33534e I don't have access to the buildbot, so cannot easily investigate more. Tom, could you have a look and see if you can find out more? Does just reverting commit c51c483d2b8ae66fe31a12509aedae02a6982ced make things OK again? Or did something else on the buildbot worker change? Note that the buildbot only does a make subdirs=elf check, not a full make check. Thanks, Mark