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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?RVfwN3a71ZVV8spgwbU+AhTP0wetZRzhI8uvfuJSy1q2+sejG2Qsd9jw+CF5?= =?us-ascii?Q?4E0bLSQWMv8ktosMjkO6mnb5VEUO2yp4vb4J5RDVCYQzXF4c1tPQPvqmaSBc?= =?us-ascii?Q?vAFsopBtjcqU1y332FbGEDqPqRVUyy9YlcFtX4G+6SWtYTOBz35oxFw8F2u2?= =?us-ascii?Q?m/ln/uq3L4C54RcfiytIZ7Yh2F5Q1HwKZq+kgMh6iWvRb8ieBEYhQNloBbLL?= =?us-ascii?Q?Udkn2ePMAPcHXEjZyPUiBjc2+CoQekL7YTJ19Zq+2sg/NA/Fvl2xwxjfggNI?= =?us-ascii?Q?eP7xVhD/0qrRG465EO5xc/MhDSsS/iCw4yqUeHVQus1CTgqYEemWMoNe8j1W?= =?us-ascii?Q?BxaZDoonPeg8swlMu61rq1YlQO1dxlyxaUYOQZ/C+s34E8ktnsBwaWX0n72l?= =?us-ascii?Q?MmpqbXY9OB2cT0S5iCvTTTutd7wH1Mw8PBn6aLKz4ylyAwyCHqnsTRjnuwsK?= =?us-ascii?Q?RJTrHx2h0GbS3S55ZbyGMSf3ADVkKAysyFSbFFeXNlAkFURNFMURZ6ITTeEz?= =?us-ascii?Q?05kPaHQdJzoi/onS3Q9jiFdbOKOGvGl9/AqP7/zcNz9O/w7BIUFlzLIo3r7q?= =?us-ascii?Q?TQIh/qiUHPdCtwpxoHRfsDUcfYUZo23syYr2tGxClPR/AwKJIao+WferI14P?= =?us-ascii?Q?UfJhG2BhoJnofFS9jBz8OT1NLKPpX/fv2AiGsIK4JP/zj6Ecf9lUIFqx7M05?= =?us-ascii?Q?v2cF7Kg6cbsdblSxeKx/D/k50Pfm/LG0WFNZudWDNoo5n0FU7dMbQ8h11sNY?= =?us-ascii?Q?FXA+SvHLk0yViqngQGpFBLFVs6p32rrPhYnwg77jHxMw4yRaJ3Rgug+2QFFY?= =?us-ascii?Q?YkS+MBNsjqBJu1+A92TtRBgb8Vw/l4maUObimHkSeGJZDKmjFgW1xKBo7Mt7?= =?us-ascii?Q?aQhoc6ZMfb836nmGW0pm5bOzIPexScGKTduPrcfL/mvPbN2iMAh62rIdmOzW?= =?us-ascii?Q?yEA2StRL4wrJ9FEG6e9Cb3QeAuCbUu3vc+Gi7FDOAJa/ho/DNenhsZ5g7sa9?= =?us-ascii?Q?CLcz3w+lxxDsEgNwPXdhfYKf58pJ4/gRIFY0dAK3lelRYTxVYU92qRo9pqVw?= =?us-ascii?Q?FJa97hIMMKdrxPVQXs38b18OL8QzJwvuo4Xu7WR+JK7nk9oWcW0IWUkCNbv9?= =?us-ascii?Q?6YpQXbtV5SEyFq8glyEAlNJYn8XzElBUfBztrEXpLMXKUNsfSfO1PdkHY1DX?= =?us-ascii?Q?8cbHd36L96VrHd0F6sz4DpPXauMZFl+jOd2FgAaE37koj3qdPtDzip6cmqnB?= =?us-ascii?Q?y00v8fBqsCiI4tD+GTh+693nsCkNA69IdzLzZswPS7tupd8or4b2fYYt2AEb?= =?us-ascii?Q?EWHhvL3pRXk47sics7QROH4FHxOnZo9WnbNFQ5fXOEkYxumORmseIAnppQSW?= =?us-ascii?Q?/AY/eiU9/AsEJSA7+jNWvqJ8+jWYs1BGU+ClAjlar0qrUXBm8buZabwJvCvb?= =?us-ascii?Q?LMIvOirQiICC6AloL4YqO87EPo/ljVOvuT7Bxd4GldQxfGUM78NCnUAdCFq5?= =?us-ascii?Q?wqygAQK8cmkskEIV9fBEm14kPw6HO/UiKSxXJsAxWfhInSU1KqlGSHJYjK2G?= =?us-ascii?Q?E5YtqGEjv89LhIH1UW32GivFj6U7vMgsMkcsCzWK?= X-MS-Exchange-CrossTenant-Network-Message-Id: b4a84238-860a-4490-4243-08dbd9d69388 X-MS-Exchange-CrossTenant-AuthSource: MN0PR11MB6206.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 31 Oct 2023 05:59:42.6085 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: Qt6dMtFVcR6tHEkVNfO1oE7ntzK68op0Dmr38Uf9ZUR4tv678LitlzRJzFRmtl04U7JkPM9iFL1pZ9RPzB7d6g== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY8PR11MB7687 X-OriginatorOrg: intel.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023-10-30 at 18:29:46 +0100, Keisuke Nishimura wrote: > should_we_balance is called for the decision to do load-balancing. > When sched ticks invoke this function, only one CPU should return > true. However, in the current code, two CPUs can return true. The > following situation, where b means busy and i means idle, is an > example, because CPU 0 and CPU 2 return true. > > [0, 1] [2, 3] > b b i b > > This fix checks if there exists an idle CPU with busy sibling(s) > after looking for a CPU on an idle core. If some idle CPUs with busy > siblings are found, just the first one should do load-balancing. > > Fixes: b1bfeab9b002 ("sched/fair: Consider the idle state of the whole core for load balance") > Signed-off-by: Keisuke Nishimura > --- > kernel/sched/fair.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 2048138ce54b..69d63fae34f4 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -11079,12 +11079,16 @@ static int should_we_balance(struct lb_env *env) > continue; > } > > - /* Are we the first idle CPU? */ > + /* > + * Are we the first idle core in a MC or higher domain It is possible that the Cluster domain is lower than a MC. cluser domain: CPUs share the same L2 MC domain: CPUs share the same LLC grep . domain*/{name,flags} domain0/name:CLS domain1/name:MC domain2/name:NUMA domain0/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_SHARE_PKG_RESOURCES SD_PREFER_SIBLING domain1/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_SHARE_PKG_RESOURCES SD_PREFER_SIBLING domain2/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_SERIALIZE SD_OVERLAP SD_NUMA So, maybe: Are we the first idle core in a non-SMT domain or higher, thanks, Chenyu > + * or the first idle CPU in a SMT domain? > + */ > return cpu == env->dst_cpu; > } > > - if (idle_smt == env->dst_cpu) > - return true; > + /* Are we the first idle CPU with busy siblings? */ > + if (idle_smt != -1) > + return idle_smt == env->dst_cpu; > > /* Are we the first CPU of this group ? */ > return group_balance_cpu(sg) == env->dst_cpu; > -- > 2.34.1 >