From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 049C2C433FE for ; Thu, 10 Feb 2022 05:25:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233325AbiBJFZc (ORCPT ); Thu, 10 Feb 2022 00:25:32 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:50344 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229678AbiBJFZa (ORCPT ); Thu, 10 Feb 2022 00:25:30 -0500 Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F1545DB2; Wed, 9 Feb 2022 21:25:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1644470732; x=1676006732; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=BN/L4/oqQxn7sbeHhVV5KCEMyRN2/eURYjfCprBCqus=; b=AZKVdEhRDuaNWJPIogDjC+WX4sBeiQULba0OuP7WfHYsQ/LU/LvZVuT4 /VRmcAhzlFD1OYDQxL9kY+c77pbtkCMfeyZEvQgwQtvEMubNNhlJf8xm0 C/hs72Q8Tcyv3AP1nS6EqOfUQ5r+zD4xvOMGRQf1qbLmTbZlkj93u4riO kzSaBYnPRquUAdnopaYEoYqGIqOZ4etbEhBfI+XAZ6cqufZe/cQp8yL+l Dhq2cQunnS7mvPBW4UlerITVyDLudcgC4qXGo8RxLYCkZ0hqQTwjzaMso h5crat19jCLh9wDS/Ao9cCqCjtOiWG/7+Z2U201DDp6+Y71N9TRV1aJty w==; X-IronPort-AV: E=McAfee;i="6200,9189,10253"; a="246997166" X-IronPort-AV: E=Sophos;i="5.88,357,1635231600"; d="scan'208";a="246997166" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Feb 2022 21:25:31 -0800 X-IronPort-AV: E=Sophos;i="5.88,357,1635231600"; d="scan'208";a="541459501" Received: from yhuang6-desk2.sh.intel.com ([10.239.13.11]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Feb 2022 21:25:29 -0800 From: Huang Ying To: Jonathan Corbet Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Huang Ying , Mel Gorman , Valentin Schneider , Peter Zijlstra , Greg Kroah-Hartman Subject: [PATCH -V3 RESEND] numa balancing: move some document to make it consistent with the code Date: Thu, 10 Feb 2022 13:25:14 +0800 Message-Id: <20220210052514.3038279-1-ying.huang@intel.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org After commit 8a99b6833c88 ("sched: Move SCHED_DEBUG sysctl to debugfs"), some NUMA balancing sysctls enclosed with SCHED_DEBUG has been moved to debugfs. This patch move the document for these sysctls from Documentation/admin-guide/sysctl/kernel.rst to Documentation/scheduler/sched-debug.rst to make the document consistent with the code. Signed-off-by: "Huang, Ying" Acked-by: Mel Gorman Reviewed-by: Valentin Schneider Cc: Peter Zijlstra (Intel) Cc: Greg Kroah-Hartman --- Documentation/admin-guide/sysctl/kernel.rst | 46 +----------------- Documentation/scheduler/index.rst | 1 + Documentation/scheduler/sched-debug.rst | 54 +++++++++++++++++++++ 3 files changed, 56 insertions(+), 45 deletions(-) create mode 100644 Documentation/scheduler/sched-debug.rst diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index d359bcfadd39..8551aeca1574 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -609,51 +609,7 @@ be migrated to a local memory node. The unmapping of pages and trapping faults incur additional overhead that ideally is offset by improved memory locality but there is no universal guarantee. If the target workload is already bound to NUMA nodes then this -feature should be disabled. Otherwise, if the system overhead from the -feature is too high then the rate the kernel samples for NUMA hinting -faults may be controlled by the `numa_balancing_scan_period_min_ms, -numa_balancing_scan_delay_ms, numa_balancing_scan_period_max_ms, -numa_balancing_scan_size_mb`_, and numa_balancing_settle_count sysctls. - - -numa_balancing_scan_period_min_ms, numa_balancing_scan_delay_ms, numa_balancing_scan_period_max_ms, numa_balancing_scan_size_mb -=============================================================================================================================== - - -Automatic NUMA balancing scans tasks address space and unmaps pages to -detect if pages are properly placed or if the data should be migrated to a -memory node local to where the task is running. Every "scan delay" the task -scans the next "scan size" number of pages in its address space. When the -end of the address space is reached the scanner restarts from the beginning. - -In combination, the "scan delay" and "scan size" determine the scan rate. -When "scan delay" decreases, the scan rate increases. The scan delay and -hence the scan rate of every task is adaptive and depends on historical -behaviour. If pages are properly placed then the scan delay increases, -otherwise the scan delay decreases. The "scan size" is not adaptive but -the higher the "scan size", the higher the scan rate. - -Higher scan rates incur higher system overhead as page faults must be -trapped and potentially data must be migrated. However, the higher the scan -rate, the more quickly a tasks memory is migrated to a local node if the -workload pattern changes and minimises performance impact due to remote -memory accesses. These sysctls control the thresholds for scan delays and -the number of pages scanned. - -``numa_balancing_scan_period_min_ms`` is the minimum time in milliseconds to -scan a tasks virtual memory. It effectively controls the maximum scanning -rate for each task. - -``numa_balancing_scan_delay_ms`` is the starting "scan delay" used for a task -when it initially forks. - -``numa_balancing_scan_period_max_ms`` is the maximum time in milliseconds to -scan a tasks virtual memory. It effectively controls the minimum scanning -rate for each task. - -``numa_balancing_scan_size_mb`` is how many megabytes worth of pages are -scanned for a given scan. - +feature should be disabled. oops_all_cpu_backtrace ====================== diff --git a/Documentation/scheduler/index.rst b/Documentation/scheduler/index.rst index 88900aabdbf7..30cca8a37b3b 100644 --- a/Documentation/scheduler/index.rst +++ b/Documentation/scheduler/index.rst @@ -17,6 +17,7 @@ Linux Scheduler sched-nice-design sched-rt-group sched-stats + sched-debug text_files diff --git a/Documentation/scheduler/sched-debug.rst b/Documentation/scheduler/sched-debug.rst new file mode 100644 index 000000000000..4d3d24f2a439 --- /dev/null +++ b/Documentation/scheduler/sched-debug.rst @@ -0,0 +1,54 @@ +================= +Scheduler debugfs +================= + +Booting a kernel with CONFIG_SCHED_DEBUG=y will give access to +scheduler specific debug files under /sys/kernel/debug/sched. Some of +those files are described below. + +numa_balancing +============== + +`numa_balancing` directory is used to hold files to control NUMA +balancing feature. If the system overhead from the feature is too +high then the rate the kernel samples for NUMA hinting faults may be +controlled by the `scan_period_min_ms, scan_delay_ms, +scan_period_max_ms, scan_size_mb` files. + + +scan_period_min_ms, scan_delay_ms, scan_period_max_ms, scan_size_mb +------------------------------------------------------------------- + +Automatic NUMA balancing scans tasks address space and unmaps pages to +detect if pages are properly placed or if the data should be migrated to a +memory node local to where the task is running. Every "scan delay" the task +scans the next "scan size" number of pages in its address space. When the +end of the address space is reached the scanner restarts from the beginning. + +In combination, the "scan delay" and "scan size" determine the scan rate. +When "scan delay" decreases, the scan rate increases. The scan delay and +hence the scan rate of every task is adaptive and depends on historical +behaviour. If pages are properly placed then the scan delay increases, +otherwise the scan delay decreases. The "scan size" is not adaptive but +the higher the "scan size", the higher the scan rate. + +Higher scan rates incur higher system overhead as page faults must be +trapped and potentially data must be migrated. However, the higher the scan +rate, the more quickly a tasks memory is migrated to a local node if the +workload pattern changes and minimises performance impact due to remote +memory accesses. These files control the thresholds for scan delays and +the number of pages scanned. + +``scan_period_min_ms`` is the minimum time in milliseconds to scan a +tasks virtual memory. It effectively controls the maximum scanning +rate for each task. + +``scan_delay_ms`` is the starting "scan delay" used for a task when it +initially forks. + +``scan_period_max_ms`` is the maximum time in milliseconds to scan a +tasks virtual memory. It effectively controls the minimum scanning +rate for each task. + +``scan_size_mb`` is how many megabytes worth of pages are scanned for +a given scan. -- 2.30.2