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Lu" CC: 'GNU C Library' Subject: [PATCH v6 3/4] Reduce CAS in malloc spinlocks Thread-Topic: [PATCH v6 3/4] Reduce CAS in malloc spinlocks Thread-Index: AQHX2iAbBw+W4VeANUumTq4MkUKt6Q== Date: Mon, 15 Nov 2021 13:01:57 +0000 Message-ID: Accept-Language: en-GB, en-US Content-Language: en-GB X-MS-Has-Attach: X-MS-TNEF-Correlator: suggested_attachment_session_id: d11dd67d-c1e1-e61a-7f62-635dfd5dac68 Authentication-Results-Original: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=arm.com; x-ms-publictraffictype: Email X-MS-Office365-Filtering-Correlation-Id: 3484a637-3f89-46fe-020b-08d9a8382343 x-ms-traffictypediagnostic: VI1PR08MB4032:|AM6PR08MB3255: X-Microsoft-Antispam-PRVS: x-checkrecipientrouted: true nodisclaimer: true x-ms-oob-tlc-oobclassifiers: OLM:8882;OLM:8882; X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam-Untrusted: BCL:0; X-Microsoft-Antispam-Message-Info-Original: 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 X-Forefront-Antispam-Report-Untrusted: CIP:255.255.255.255; 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CTRY:IE; LANG:en; SCL:1; SRV:; IPV:CAL; SFV:NSPM; H:64aa7808-outbound-1.mta.getcheckrecipient.com; PTR:ec2-63-35-35-123.eu-west-1.compute.amazonaws.com; CAT:NONE; SFS:(4636009)(36840700001)(46966006)(7696005)(508600001)(336012)(83380400001)(4744005)(4326008)(6506007)(33656002)(47076005)(316002)(8676002)(36860700001)(55016002)(82310400003)(52536014)(5660300002)(86362001)(6862004)(8936002)(26005)(2906002)(70586007)(186003)(81166007)(70206006)(356005)(9686003); DIR:OUT; SFP:1101; X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Nov 2021 13:02:11.2784 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 3484a637-3f89-46fe-020b-08d9a8382343 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d; Ip=[63.35.35.123]; Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: DB5EUR03FT033.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM6PR08MB3255 X-Spam-Status: No, score=-6.1 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_PASS, SPF_PASS, TXREP, UNPARSEABLE_RELAY 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: Mon, 15 Nov 2021 13:02:17 -0000 Hi,=0A= =0A= A quick check shows that the atomic loads are always inserted before the fi= rst=0A= CAS, and since these locks are mostly uncontended, this will actually hurt= =0A= performance on all targets. Also, it's not like we've ever had complaints a= bout=0A= the number of arenas we can create in malloc by having all CPUs create one = at=0A= exactly the same time...=0A= =0A= So a change like this really need to show gains in malloc benchmarks.=0A= =0A= Cheers,=0A= Wilco=