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Greg Kroah-Hartman committed Apr 20, 2008
1 parent 1422817 commit e45bcdb
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2 changes: 1 addition & 1 deletion [refs]
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---
refs/heads/master: 529a41e36673b518c9e091f3a8d932b6b9e3c461
refs/heads/master: c1ebdae514a356c71c09035f5141d94aab5e8fe4
6 changes: 3 additions & 3 deletions trunk/Documentation/DocBook/kernel-locking.tmpl
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Expand Up @@ -241,7 +241,7 @@
</para>
<para>
The third type is a semaphore
(<filename class="headerfile">include/linux/semaphore.h</filename>): it
(<filename class="headerfile">include/asm/semaphore.h</filename>): it
can have more than one holder at any time (the number decided at
initialization time), although it is most commonly used as a
single-holder lock (a mutex). If you can't get a semaphore, your
Expand Down Expand Up @@ -290,7 +290,7 @@
<para>
If you have a data structure which is only ever accessed from
user context, then you can use a simple semaphore
(<filename>linux/linux/semaphore.h</filename>) to protect it. This
(<filename>linux/asm/semaphore.h</filename>) to protect it. This
is the most trivial case: you initialize the semaphore to the number
of resources available (usually 1), and call
<function>down_interruptible()</function> to grab the semaphore, and
Expand Down Expand Up @@ -1656,7 +1656,7 @@ the amount of locking which needs to be done.
#include &lt;linux/slab.h&gt;
#include &lt;linux/string.h&gt;
+#include &lt;linux/rcupdate.h&gt;
#include &lt;linux/semaphore.h&gt;
#include &lt;asm/semaphore.h&gt;
#include &lt;asm/errno.h&gt;

struct object
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72 changes: 2 additions & 70 deletions trunk/Documentation/cpusets.txt
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Expand Up @@ -8,7 +8,6 @@ Portions Copyright (c) 2004-2006 Silicon Graphics, Inc.
Modified by Paul Jackson <pj@sgi.com>
Modified by Christoph Lameter <clameter@sgi.com>
Modified by Paul Menage <menage@google.com>
Modified by Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>

CONTENTS:
=========
Expand All @@ -21,8 +20,7 @@ CONTENTS:
1.5 What is memory_pressure ?
1.6 What is memory spread ?
1.7 What is sched_load_balance ?
1.8 What is sched_relax_domain_level ?
1.9 How do I use cpusets ?
1.8 How do I use cpusets ?
2. Usage Examples and Syntax
2.1 Basic Usage
2.2 Adding/removing cpus
Expand Down Expand Up @@ -499,73 +497,7 @@ the cpuset code to update these sched domains, it compares the new
partition requested with the current, and updates its sched domains,
removing the old and adding the new, for each change.


1.8 What is sched_relax_domain_level ?
--------------------------------------

In sched domain, the scheduler migrates tasks in 2 ways; periodic load
balance on tick, and at time of some schedule events.

When a task is woken up, scheduler try to move the task on idle CPU.
For example, if a task A running on CPU X activates another task B
on the same CPU X, and if CPU Y is X's sibling and performing idle,
then scheduler migrate task B to CPU Y so that task B can start on
CPU Y without waiting task A on CPU X.

And if a CPU run out of tasks in its runqueue, the CPU try to pull
extra tasks from other busy CPUs to help them before it is going to
be idle.

Of course it takes some searching cost to find movable tasks and/or
idle CPUs, the scheduler might not search all CPUs in the domain
everytime. In fact, in some architectures, the searching ranges on
events are limited in the same socket or node where the CPU locates,
while the load balance on tick searchs all.

For example, assume CPU Z is relatively far from CPU X. Even if CPU Z
is idle while CPU X and the siblings are busy, scheduler can't migrate
woken task B from X to Z since it is out of its searching range.
As the result, task B on CPU X need to wait task A or wait load balance
on the next tick. For some applications in special situation, waiting
1 tick may be too long.

The 'sched_relax_domain_level' file allows you to request changing
this searching range as you like. This file takes int value which
indicates size of searching range in levels ideally as follows,
otherwise initial value -1 that indicates the cpuset has no request.

-1 : no request. use system default or follow request of others.
0 : no search.
1 : search siblings (hyperthreads in a core).
2 : search cores in a package.
3 : search cpus in a node [= system wide on non-NUMA system]
( 4 : search nodes in a chunk of node [on NUMA system] )
( 5~ : search system wide [on NUMA system])

This file is per-cpuset and affect the sched domain where the cpuset
belongs to. Therefore if the flag 'sched_load_balance' of a cpuset
is disabled, then 'sched_relax_domain_level' have no effect since
there is no sched domain belonging the cpuset.

If multiple cpusets are overlapping and hence they form a single sched
domain, the largest value among those is used. Be careful, if one
requests 0 and others are -1 then 0 is used.

Note that modifying this file will have both good and bad effects,
and whether it is acceptable or not will be depend on your situation.
Don't modify this file if you are not sure.

If your situation is:
- The migration costs between each cpu can be assumed considerably
small(for you) due to your special application's behavior or
special hardware support for CPU cache etc.
- The searching cost doesn't have impact(for you) or you can make
the searching cost enough small by managing cpuset to compact etc.
- The latency is required even it sacrifices cache hit rate etc.
then increasing 'sched_relax_domain_level' would benefit you.


1.9 How do I use cpusets ?
1.8 How do I use cpusets ?
--------------------------

In order to minimize the impact of cpusets on critical kernel
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15 changes: 0 additions & 15 deletions trunk/Documentation/feature-removal-schedule.txt
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Expand Up @@ -282,13 +282,6 @@ Why: Not used in-tree. The current out-of-tree users used it to
out-of-tree driver.
Who: Thomas Gleixner <tglx@linutronix.de>

----------------------------

What: usedac i386 kernel parameter
When: 2.6.27
Why: replaced by allowdac and no dac combination
Who: Glauber Costa <gcosta@redhat.com>

---------------------------

What: /sys/o2cb symlink
Expand All @@ -298,11 +291,3 @@ Why: /sys/fs/o2cb is the proper location for this information - /sys/o2cb
ocfs2-tools. 2 years should be sufficient time to phase in new versions
which know to look in /sys/fs/o2cb.
Who: ocfs2-devel@oss.oracle.com

---------------------------

What: asm/semaphore.h
When: 2.6.26
Why: Implementation became generic; users should now include
linux/semaphore.h instead.
Who: Matthew Wilcox <willy@linux.intel.com>
10 changes: 1 addition & 9 deletions trunk/Documentation/kernel-parameters.txt
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Expand Up @@ -1280,16 +1280,8 @@ and is between 256 and 4096 characters. It is defined in the file
noexec [IA-64]

noexec [X86-32,X86-64]
On X86-32 available only on PAE configured kernels.
noexec=on: enable non-executable mappings (default)
noexec=off: disable non-executable mappings

noexec32 [X86-64]
This affects only 32-bit executables.
noexec32=on: enable non-executable mappings (default)
read doesn't imply executable mappings
noexec32=off: disable non-executable mappings
read implies executable mappings
noexec=off: disable nn-executable mappings

nofxsr [BUGS=X86-32] Disables x86 floating point extended
register save and restore. The kernel will only save
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96 changes: 0 additions & 96 deletions trunk/Documentation/prctl/disable-tsc-ctxt-sw-stress-test.c

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95 changes: 0 additions & 95 deletions trunk/Documentation/prctl/disable-tsc-on-off-stress-test.c

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