From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id 7DF3738582B1 for ; Tue, 16 Aug 2022 07:31:56 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 7DF3738582B1 Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-641-I6gfTGOkM1eII7HucKfibg-1; Tue, 16 Aug 2022 03:31:52 -0400 X-MC-Unique: I6gfTGOkM1eII7HucKfibg-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6B654811E80; Tue, 16 Aug 2022 07:31:52 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.98]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 366A0492CA5; Tue, 16 Aug 2022 07:31:51 +0000 (UTC) From: Florian Weimer To: Thomas Fitzsimmons Cc: Mark Wielaard , 'GNU C Library' , Wilco Dijkstra Subject: Re: [PATCH] Improve performance of IO locks References: Date: Tue, 16 Aug 2022 09:31:49 +0200 In-Reply-To: (Thomas Fitzsimmons's message of "Mon, 15 Aug 2022 23:07:03 -0400") Message-ID: <878rnoeja2.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-5.0 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham 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: Tue, 16 Aug 2022 07:31:58 -0000 * Thomas Fitzsimmons: > Hi Mark, > > Mark Wielaard writes: > >> 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? > > Yes reverting that commit, the result is: > > Summary of test results: > 317 PASS > 10 UNSUPPORTED > 2 XPASS > > Without the reversion: > > Summary of test results: > 256 FAIL > 68 PASS > 3 UNSUPPORTED > 2 XFAIL > > I looked at elf/unload as an example; it's segfaulting in > _dl_relocate_object, backtrace attached; not sure what else to check. I don't see this on powerpc64, with a toolchain based on GCC 8.2 and binutils 2.30. I'm at a loss how these things could be related. Thanks, Florian