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 15A013858D28 for ; Tue, 12 Apr 2022 11:53:23 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 15A013858D28 Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-473-X0mKjNtBPrmzlzwbv3HDcw-1; Tue, 12 Apr 2022 07:53:17 -0400 X-MC-Unique: X0mKjNtBPrmzlzwbv3HDcw-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 9707C1C12DE3; Tue, 12 Apr 2022 11:53:16 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.193.61]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8CB7E406793; Tue, 12 Apr 2022 11:53:15 +0000 (UTC) From: Florian Weimer To: Adhemerval Zanella via Libc-alpha Cc: Noah Goldstein , Adhemerval Zanella , Wangyang Guo Subject: Re: [PATCH v2] nptl: Add backoff mechanism to spinlock loop References: <20220328084705.468207-1-wangyang.guo@intel.com> <97b1105f-42e8-a347-f82e-c81e548f0c2f@linaro.org> <82d5d195-aea0-f817-bfc1-5822829728c7@linaro.org> Date: Tue, 12 Apr 2022 13:53:13 +0200 In-Reply-To: <82d5d195-aea0-f817-bfc1-5822829728c7@linaro.org> (Adhemerval Zanella via Libc-alpha's message of "Wed, 30 Mar 2022 14:21:10 -0300") Message-ID: <87wnfufrh2.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 10.11.54.10 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-5.4 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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, 12 Apr 2022 11:53:24 -0000 * Adhemerval Zanella via Libc-alpha: > On 30/03/2022 14:07, Noah Goldstein wrote: >> What would be the best init jitter for arch w/ only syscall timers? TID? Or >> something else? > > We don't cached the TID anymore, so it would still generate syscalls. We do have the TID for the running process in the TCB. We need it (or something like it) for recursive locks. Maybe for this application, we should use some number of upper bits from a per-thread linear consequential generator, initialized to a random value at thread start? Thanks, Florian