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From: riel@redhat.com
To: tj@kernel.org
Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
	lizefan@huawei.com, Rik van Riel <riel@redhat.com>
Subject: [PATCH 4/4] cpuset,isolcpus: document relationship between cpusets & isolcpus
Date: Mon,  9 Mar 2015 12:12:10 -0400	[thread overview]
Message-ID: <1425917530-1771-5-git-send-email-riel@redhat.com> (raw)
In-Reply-To: <1425917530-1771-1-git-send-email-riel@redhat.com>

From: Rik van Riel <riel@redhat.com>

Document the subtly changed relationship between cpusets and isolcpus.
Turns out the old documentation did not match the code...

Signed-off-by: Rik van Riel <riel@redhat.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
---
 Documentation/cgroups/cpusets.txt | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/Documentation/cgroups/cpusets.txt b/Documentation/cgroups/cpusets.txt
index f2235a162529..fdf7dff3f607 100644
--- a/Documentation/cgroups/cpusets.txt
+++ b/Documentation/cgroups/cpusets.txt
@@ -392,8 +392,10 @@ Put simply, it costs less to balance between two smaller sched domains
 than one big one, but doing so means that overloads in one of the
 two domains won't be load balanced to the other one.
 
-By default, there is one sched domain covering all CPUs, except those
-marked isolated using the kernel boot time "isolcpus=" argument.
+By default, there is one sched domain covering all CPUs, including those
+marked isolated using the kernel boot time "isolcpus=" argument. However,
+the isolated CPUs will not participate in load balancing, and will not
+have tasks running on them unless explicitly assigned.
 
 This default load balancing across all CPUs is not well suited for
 the following two situations:
@@ -465,6 +467,10 @@ such partially load balanced cpusets, as they may be artificially
 constrained to some subset of the CPUs allowed to them, for lack of
 load balancing to the other CPUs.
 
+CPUs in "cpuset.isolcpus" were excluded from load balancing by the
+isolcpus= kernel boot option, and will never be load balanced regardless
+of the value of "cpuset.sched_load_balance" in any cpuset.
+
 1.7.1 sched_load_balance implementation details.
 ------------------------------------------------
 
-- 
2.1.0


  parent reply	other threads:[~2015-03-09 16:12 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-09 16:12 [PATCH v4 RESEND 0/4] cpusets,isolcpus: exclude isolcpus from load balancing in cpusets riel
2015-03-09 16:12 ` [PATCH 1/4] sched,isolcpu: make cpu_isolated_map visible outside scheduler riel
2015-03-09 16:12 ` [PATCH 2/4] cpusets,isolcpus: exclude isolcpus from load balancing in cpusets riel
2015-03-09 16:12 ` [PATCH 3/4] cpusets,isolcpus: add file to show isolated cpus in cpuset riel
2015-03-18 16:47   ` Tejun Heo
2015-03-18 23:40     ` Rik van Riel
2015-03-19  1:50       ` Zefan Li
2015-03-19  1:54         ` Rik van Riel
2015-03-19  6:28           ` Zefan Li
2015-03-19  1:45     ` Rik van Riel
2015-03-19  1:48       ` Tejun Heo
2015-03-09 16:12 ` riel [this message]
2015-03-18 16:13 ` [PATCH v4 RESEND 0/4] cpusets,isolcpus: exclude isolcpus from load balancing in cpusets Rik van Riel
2015-03-19 18:30 ` Tejun Heo
  -- strict thread matches above, loose matches on Subject: below --
2015-03-03 23:00 [PATCH v4 " riel
2015-03-03 23:00 ` [PATCH 4/4] cpuset,isolcpus: document relationship between cpusets & isolcpus riel

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