Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757995Ab3IYBRf (ORCPT ); Tue, 24 Sep 2013 21:17:35 -0400 Received: from e8.ny.us.ibm.com ([32.97.182.138]:37536 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755154Ab3IYBRd (ORCPT ); Tue, 24 Sep 2013 21:17:33 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 2/3] kthread: Add pointer to vmstat-avoidance patch Date: Tue, 24 Sep 2013 18:17:22 -0700 Message-Id: <1380071843-30362-2-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1380071843-30362-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20130925011657.GA29958@linux.vnet.ibm.com> <1380071843-30362-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13092501-0320-0000-0000-0000011D9A44 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2097 Lines: 43 From: "Paul E. McKenney" Signed-off-by: Paul E. McKenney --- Documentation/kernel-per-CPU-kthreads.txt | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/Documentation/kernel-per-CPU-kthreads.txt b/Documentation/kernel-per-CPU-kthreads.txt index 32351bf..827104f 100644 --- a/Documentation/kernel-per-CPU-kthreads.txt +++ b/Documentation/kernel-per-CPU-kthreads.txt @@ -181,12 +181,17 @@ To reduce its OS jitter, do any of the following: make sure that this is safe on your particular system. d. It is not possible to entirely get rid of OS jitter from vmstat_update() on CONFIG_SMP=y systems, but you - can decrease its frequency by writing a large value to - /proc/sys/vm/stat_interval. The default value is HZ, - for an interval of one second. Of course, larger values - will make your virtual-memory statistics update more - slowly. Of course, you can also run your workload at - a real-time priority, thus preempting vmstat_update(). + can decrease its frequency by writing a large value + to /proc/sys/vm/stat_interval. The default value is + HZ, for an interval of one second. Of course, larger + values will make your virtual-memory statistics update + more slowly. Of course, you can also run your workload + at a real-time priority, thus preempting vmstat_update(), + but if your workload is CPU-bound, this is a bad idea. + However, there is an RFC patch from Christoph Lameter + (based on an earlier one from Gilad Ben-Yossef) that + reduces or even eliminates vmstat overhead for some + workloads at https://lkml.org/lkml/2013/9/4/379. e. If running on high-end powerpc servers, build with CONFIG_PPC_RTAS_DAEMON=n. This prevents the RTAS daemon from running on each CPU every second or so. -- 1.8.1.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/