Commit graph

36 commits

Author SHA1 Message Date
Rusty Russell
082edb7bf4 numa, cpumask: move numa_node_id default implementation to topology.h
Impact: cleanup, potential bugfix

Not sure what changed to expose this, but clearly that numa_node_id()
doesn't belong in mmzone.h (the inline in gfp.h is probably overkill, too).

In file included from include/linux/topology.h:34,
                 from arch/x86/mm/numa.c:2:
/home/rusty/patches-cpumask/linux-2.6/arch/x86/include/asm/topology.h:64:1: warning: "numa_node_id" redefined
In file included from include/linux/topology.h:32,
                 from arch/x86/mm/numa.c:2:
include/linux/mmzone.h:770:1: warning: this is the location of the previous definition

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Mike Travis <travis@sgi.com>
LKML-Reference: <200903132343.37661.rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-13 14:35:31 +01:00
Rusty Russell
a70f730282 cpumask: replace node_to_cpumask with cpumask_of_node.
Impact: cleanup

node_to_cpumask (and the blecherous node_to_cpumask_ptr which
contained a declaration) are replaced now everyone implements
cpumask_of_node.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2009-03-13 14:49:46 +10:30
Rusty Russell
fbd59a8d1f cpumask: Use topology_core_cpumask()/topology_thread_cpumask()
Impact: reduce stack usage, use new cpumask API.

This actually uses topology_core_cpumask() and
topology_thread_cpumask(), removing the only users of
topology_core_siblings() and topology_thread_siblings()

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Mike Travis <travis@sgi.com>
Cc: linux-net-drivers@solarflare.com
2009-01-11 19:12:49 +01:00
Vaidyanathan Srinivasan
100fdaee70 sched: add SD_BALANCE_NEWIDLE at MC and CPU level for sched_mc>0
Impact: change task balancing to save power more agressively

Add SD_BALANCE_NEWIDLE flag at MC level and CPU level
if sched_mc is set.  This helps power savings and
will not affect performance when sched_mc=0

Ingo and Mike Galbraith have optimised the SD flags by
removing SD_BALANCE_NEWIDLE at MC and CPU level.  This
helps performance but hurts power savings since this
slows down task consolidation by reducing the number
of times load_balance is run.

    sched: fine-tune SD_MC_INIT
        commit 1480098470
        Author: Mike Galbraith <efault@gmx.de>
        Date:   Fri Nov 7 15:26:50 2008 +0100

    sched: re-tune balancing -- revert
        commit 9fcd18c9e6
        Author: Ingo Molnar <mingo@elte.hu>
        Date:   Wed Nov 5 16:52:08 2008 +0100

This patch selectively enables SD_BALANCE_NEWIDLE flag
only when sched_mc is set to 1 or 2.  This helps power savings
by task consolidation and also does not hurt performance at
sched_mc=0 where all power saving optimisations are turned off.

Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-19 09:21:55 +01:00
Vaidyanathan Srinivasan
716707b299 sched: convert BALANCE_FOR_xx_POWER to inline functions
Impact: cleanup

BALANCE_FOR_MC_POWER and similar macros defined in sched.h are
not constants and have various condition checks and significant
amount of code that is not suitable to be contain in a macro.
Also there could be side effects on the expressions passed to
some of them like test_sd_parent().

This patch converts all complex macros related to power savings
balance to inline functions.

Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-19 09:21:45 +01:00
Heiko Carstens
ee79d1bdb6 sched: let arch_update_cpu_topology indicate if topology changed
Change arch_update_cpu_topology so it returns 1 if the cpu topology changed
and 0 if it didn't change. This will be useful for the next patch which adds
a call to this function in partition_sched_domains.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-12 13:47:21 +01:00
Ingo Molnar
52c642f33b sched: fine-tune SD_SIBLING_INIT
fine-tune the HT sched-domains parameters as well.

On a HT capable box, this increases lat_ctx performance from 23.87
usecs to 1.49 usecs:

 # before

 $ ./lat_ctx -s 0 2

   "size=0k ovr=1.89
    2 23.87

 # after

 $ ./lat_ctx -s 0 2

   "size=0k ovr=1.84
     2 1.49

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-07 16:09:23 +01:00
Mike Galbraith
1480098470 sched: fine-tune SD_MC_INIT
Tune SD_MC_INIT the same way as SD_CPU_INIT:
unset SD_BALANCE_NEWIDLE, and set SD_WAKE_BALANCE.

This improves vmark by 5%:

vmark         132102 125968 125497 messages/sec    avg 127855.66    .984
vmark         139404 131719 131272 messages/sec    avg 134131.66   1.033

Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

 # *DOCUMENTATION*
2008-11-07 15:35:11 +01:00
Ingo Molnar
9fcd18c9e6 sched: re-tune balancing
Impact: improve wakeup affinity on NUMA systems, tweak SMP systems

Given the fixes+tweaks to the wakeup-buddy code, re-tweak the domain
balancing defaults on NUMA and SMP systems.

Turn on SD_WAKE_AFFINE which was off on x86 NUMA - there's no reason
why we would not want to have wakeup affinity across nodes as well.
(we already do this in the standard NUMA template.)

lat_ctx on a NUMA box is particularly happy about this change:

before:

 |   phoenix:~/l> ./lat_ctx -s 0 2
 |   "size=0k ovr=2.60
 |   2 5.70

after:

 |   phoenix:~/l> ./lat_ctx -s 0 2
 |   "size=0k ovr=2.65
 |   2 2.07

a 2.75x speedup.

pipe-test is similarly happy about it too:

 |  phoenix:~/sched-tests> ./pipe-test
 |   18.26 usecs/loop.
 |   14.70 usecs/loop.
 |   14.38 usecs/loop.
 |   10.55 usecs/loop.              # +WAKE_AFFINE on domain0+domain1
 |   8.63 usecs/loop.
 |   8.59 usecs/loop.
 |   9.03 usecs/loop.
 |   8.94 usecs/loop.
 |   8.96 usecs/loop.
 |   8.63 usecs/loop.

Also:

 - disable SD_BALANCE_NEWIDLE on NUMA and SMP domains (keep it for siblings)
 - enable SD_WAKE_BALANCE on SMP domains

Sysbench+postgresql improves all around the board, quite significantly:

           .28-rc3-11474e2c  .28-rc3-11474e2c-tune
-------------------------------------------------
    1:             571              688    +17.08%
    2:            1236             1206    -2.55%
    4:            2381             2642    +9.89%
    8:            4958             5164    +3.99%
   16:            9580             9574    -0.07%
   32:            7128             8118    +12.20%
   64:            7342             8266    +11.18%
  128:            7342             8064    +8.95%
  256:            7519             7884    +4.62%
  512:            7350             7731    +4.93%
-------------------------------------------------
  SUM:           55412            59341    +6.62%

So it's a win both for the runup portion, the peak area and the tail.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-05 18:04:38 +01:00
Ben Hutchings
c50cbb05a0 cpu topology: always define CPU topology information
This can result in an empty topology directory in sysfs, and requires
in-kernel users to protect all uses with #ifdef - see
<http://marc.info/?l=linux-netdev&m=120639033904472&w=2>.

The documentation of CPU topology specifies what the defaults should be if
only partial information is available from the hardware.  So we can
provide these defaults as a fallback.

This patch:

- Adds default definitions of the 4 topology macros to <linux/topology.h>
- Changes drivers/base/topology.c to use the topology macros unconditionally
  and to cope with definitions that aren't lvalues
- Updates documentation accordingly

[ From: Andrew Morton <akpm@linux-foundation.org>
  - fold now-duplicated code
  - fix layout
]

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Chandra Seetharaman <sekharan@us.ibm.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Mike Travis <travis@sgi.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: John Hawkes <hawkes@sgi.com>
Cc: Zhang, Yanmin <yanmin.zhang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-13 10:09:46 +02:00
Ingo Molnar
ea3f01f8af sched: re-tune NUMA topologies
improve the sysbench ramp-up phase and its peak throughput on
a 16way NUMA box, by turning on WAKE_AFFINE:

             tip/sched   tip/sched+wake-affine
-------------------------------------------------
    1:             700              830    +15.65%
    2:            1465             1391    -5.28%
    4:            3017             3105    +2.81%
    8:            5100             6021    +15.30%
   16:           10725            10745    +0.19%
   32:           10135            10150    +0.16%
   64:            9338             9240    -1.06%
  128:            8599             8252    -4.21%
  256:            8475             8144    -4.07%
-------------------------------------------------
  SUM:           57558            57882    +0.56%

this change also improves lat_ctx from 6.69 usecs to 1.11 usec:

  $ ./lat_ctx -s 0 2
  "size=0k ovr=1.19
  2 1.11

  $ ./lat_ctx -s 0 2
  "size=0k ovr=1.22
  2 6.69

in sysbench it's an overall win with some weakness at the lots-of-clients
side. That happens because we now under-balance this workload
a bit. To counter that effect, turn on NEWIDLE:

              wake-idle          wake-idle+newidle
 -------------------------------------------------
     1:             830              834    +0.43%
     2:            1391             1401    +0.65%
     4:            3105             3091    -0.43%
     8:            6021             6046    +0.42%
    16:           10745            10736    -0.08%
    32:           10150            10206    +0.55%
    64:            9240             9533    +3.08%
   128:            8252             8355    +1.24%
   256:            8144             8384    +2.87%
 -------------------------------------------------
   SUM:           57882            58591    +1.21%

as a bonus this not only improves the many-clients case but
also improves the (more important) rampup phase.

sysbench is a workload that quickly breaks down if the
scheduler over-balances, so since it showed an improvement
under NEWIDLE this change is definitely good.
2008-05-29 14:46:30 +02:00
Mike Travis
7c16ec585c cpumask: reduce stack usage in SD_x_INIT initializers
* Remove empty cpumask_t (and all non-zero/non-null) variables
    in SD_*_INIT macros.  Use memset(0) to clear.  Also, don't
    inline the initializer functions to save on stack space in
    build_sched_domains().

  * Merge change to include/linux/topology.h that uses the new
    node_to_cpumask_ptr function in the nr_cpus_node macro into
    this patch.

Depends on:
	[mm-patch]: asm-generic-add-node_to_cpumask_ptr-macro.patch
	[sched-devel]: sched: add new set_cpus_allowed_ptr function

Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-04-19 19:44:59 +02:00
Heiko Carstens
22e52b072d sched: add arch_update_cpu_topology hook.
Will be called each time the scheduling domains are rebuild.
Needed for architectures that don't have a static cpu topology.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-03-21 16:43:48 +01:00
Ingo Molnar
33b0c4217d sched: tune multi-core idle balancing
WAKE_IDLE is too agressive on multi-core CPUs with the new
wake-affine code, keep it on for SMT/HT balancing alone
(where there's no cache affinity at all between logical CPUs).

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-03-19 04:27:53 +01:00
Ingo Molnar
32525d022a sched: whitespace cleanups in topology.h
whitespace cleanups in topology.h.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-01-25 21:08:20 +01:00
Ingo Molnar
52d853431e sched: reactivate fork balancing
reactivate fork balancing.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-01-25 21:08:20 +01:00
Ingo Molnar
7a6c6bcee0 sched: enable wake-idle on CONFIG_SCHED_MC=y
most multicore CPUs today have shared L2 caches, so tune things so
that the spreading amongst cores is more aggressive.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2007-10-15 17:00:19 +02:00
Ingo Molnar
95dbb421d1 sched: reintroduce topology.h tunings
reintroduce the 2.6.22 topology.h tunings again - they result in
slightly better balancing.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2007-10-15 17:00:19 +02:00
Ingo Molnar
362a701663 [PATCH] sched: remove cache_hot_time
remove the last unused remains of cache_hot_time.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2007-08-02 17:41:40 +02:00
Ingo Molnar
f787a50306 [PATCH] sched: small topology.h cleanup
trivial cleanup: LOCAL_DISTANCE and REMOTE_DISTANCE are only used in
topology.h and inside an #ifndef section - limit their existence to
that #ifndef.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-13 10:11:52 -07:00
Ingo Molnar
9c4801cebc sched: more agressive idle balancing
the Linux scheduler is starving a number of workloads. So default
to more agressive idle-balancing. This hurts lmbench context-switching
numbers (which was the main reason we sucked at idle-balancing for
such a long time) but the lmbench numbers are fine once the system is
minimally utilized.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2007-07-09 18:52:01 +02:00
Con Kolivas
69f7c0a1be [PATCH] sched: remove SMT nice
Remove the SMT-nice feature which idles sibling cpus on SMT cpus to
facilitiate nice working properly where cpu power is shared.  The idling of
cpus in the presence of runnable tasks is considered too fragile, easy to
break with outside code, and the complexity of managing this system if an
architecture comes along with many logical cores sharing cpu power will be
unworkable.

Remove the associated per_cpu_gain variable in sched_domains used only by
this code.

Also:

  The reason is that with dynticks enabled, this code breaks without yet
  further tweaks so dynticks brought on the rapid demise of this code.  So
  either we tweak this code or kill it off entirely.  It was Ingo's preference
  to kill it off.  Either way this needs to happen for 2.6.21 since dynticks
  has gone in.

Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-03-05 07:57:51 -08:00
Christoph Lameter
08c183f31b [PATCH] sched: add option to serialize load balancing
Large sched domains can be very expensive to scan.  Add an option SD_SERIALIZE
to the sched domain flags.  If that flag is set then we make sure that no
other such domain is being balanced.

[akpm@osdl.org: build fix]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-10 09:55:43 -08:00
Siddha, Suresh B
ac7d550499 [PATCH] sched domain: increase the SMT busy rebalance interval
With SMT, if the logical processor is busy, load balance happens for every
8msec(min)-16msec(max).  There is no need to do this often, as this is just
for fairness(to maintain uniform runqueue lengths) and default time slice
anyhow is 100msec.

Appended patch increases this interval to 64msec(min)-128msec(max) when the
logical processor is busy.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-10 09:55:42 -08:00
Siddha, Suresh B
89c4710ee9 [PATCH] sched: cleanup sched_group cpu_power setup
Up to now sched group's cpu_power for each sched domain is initialized
independently.  This made the setup code ugly as the new sched domains are
getting added.

Make the sched group cpu_power setup code generic, by using domain child
field and new domain flag in sched_domain.  For most of the sched
domains(except NUMA), sched group's cpu_power is now computed generically
using the domain properties of itself and of the child domain.

sched groups in NUMA domains are setup little differently and hence they
don't use this generic mechanism.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:04:06 -07:00
Siddha, Suresh B
1a84887080 [PATCH] sched: introduce child field in sched_domain
Introduce the child field in sched_domain struct and use it in
sched_balance_self().

We will also use this field in cleaning up the sched group cpu_power
setup(done in a different patch) code.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:04:06 -07:00
Siddha, Suresh B
5c45bf279d [PATCH] sched: mc/smt power savings sched policy
sysfs entries 'sched_mc_power_savings' and 'sched_smt_power_savings' in
/sys/devices/system/cpu/ control the MC/SMT power savings policy for the
scheduler.

Based on the values (1-enable, 0-disable) for these controls, sched groups
cpu power will be determined for different domains.  When power savings
policy is enabled and under light load conditions, scheduler will minimize
the physical packages/cpu cores carrying the load and thus conserving
power(with a perf impact based on the workload characteristics...  see OLS
2005 CMP kernel scheduler paper for more details..)

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Con Kolivas <kernel@kolivas.org>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-27 17:32:45 -07:00
Siddha, Suresh B
1e9f28fa1e [PATCH] sched: new sched domain for representing multi-core
Add a new sched domain for representing multi-core with shared caches
between cores.  Consider a dual package system, each package containing two
cores and with last level cache shared between cores with in a package.  If
there are two runnable processes, with this appended patch those two
processes will be scheduled on different packages.

On such systems, with this patch we have observed 8% perf improvement with
specJBB(2 warehouse) benchmark and 35% improvement with CFP2000 rate(with 2
users).

This new domain will come into play only on multi-core systems with shared
caches.  On other systems, this sched domain will be removed by domain
degeneration code.  This new domain can be also used for implementing power
savings policy (see OLS 2005 CMP kernel scheduler paper for more details..
I will post another patch for power savings policy soon)

Most of the arch/* file changes are for cpu_coregroup_map() implementation.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-27 08:44:43 -08:00
Christoph Lameter
9eeff2395e [PATCH] Zone reclaim: Reclaim logic
Some bits for zone reclaim exists in 2.6.15 but they are not usable.  This
patch fixes them up, removes unused code and makes zone reclaim usable.

Zone reclaim allows the reclaiming of pages from a zone if the number of
free pages falls below the watermarks even if other zones still have enough
pages available.  Zone reclaim is of particular importance for NUMA
machines.  It can be more beneficial to reclaim a page than taking the
performance penalties that come with allocating a page on a remote zone.

Zone reclaim is enabled if the maximum distance to another node is higher
than RECLAIM_DISTANCE, which may be defined by an arch.  By default
RECLAIM_DISTANCE is 20.  20 is the distance to another node in the same
component (enclosure or motherboard) on IA64.  The meaning of the NUMA
distance information seems to vary by arch.

If zone reclaim is not successful then no further reclaim attempts will
occur for a certain time period (ZONE_RECLAIM_INTERVAL).

This patch was discussed before. See

http://marc.theaimsgroup.com/?l=linux-kernel&m=113519961504207&w=2
http://marc.theaimsgroup.com/?l=linux-kernel&m=113408418232531&w=2
http://marc.theaimsgroup.com/?l=linux-kernel&m=113389027420032&w=2
http://marc.theaimsgroup.com/?l=linux-kernel&m=113380938612205&w=2

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-18 19:20:17 -08:00
akpm@osdl.org
198e2f1811 [PATCH] scheduler cache-hot-autodetect
)

From: Ingo Molnar <mingo@elte.hu>

This is the latest version of the scheduler cache-hot-auto-tune patch.

The first problem was that detection time scaled with O(N^2), which is
unacceptable on larger SMP and NUMA systems. To solve this:

- I've added a 'domain distance' function, which is used to cache
  measurement results. Each distance is only measured once. This means
  that e.g. on NUMA distances of 0, 1 and 2 might be measured, on HT
  distances 0 and 1, and on SMP distance 0 is measured. The code walks
  the domain tree to determine the distance, so it automatically follows
  whatever hierarchy an architecture sets up. This cuts down on the boot
  time significantly and removes the O(N^2) limit. The only assumption
  is that migration costs can be expressed as a function of domain
  distance - this covers the overwhelming majority of existing systems,
  and is a good guess even for more assymetric systems.

  [ People hacking systems that have assymetries that break this
    assumption (e.g. different CPU speeds) should experiment a bit with
    the cpu_distance() function. Adding a ->migration_distance factor to
    the domain structure would be one possible solution - but lets first
    see the problem systems, if they exist at all. Lets not overdesign. ]

Another problem was that only a single cache-size was used for measuring
the cost of migration, and most architectures didnt set that variable
up. Furthermore, a single cache-size does not fit NUMA hierarchies with
L3 caches and does not fit HT setups, where different CPUs will often
have different 'effective cache sizes'. To solve this problem:

- Instead of relying on a single cache-size provided by the platform and
  sticking to it, the code now auto-detects the 'effective migration
  cost' between two measured CPUs, via iterating through a wide range of
  cachesizes. The code searches for the maximum migration cost, which
  occurs when the working set of the test-workload falls just below the
  'effective cache size'. I.e. real-life optimized search is done for
  the maximum migration cost, between two real CPUs.

  This, amongst other things, has the positive effect hat if e.g. two
  CPUs share a L2/L3 cache, a different (and accurate) migration cost
  will be found than between two CPUs on the same system that dont share
  any caches.

(The reliable measurement of migration costs is tricky - see the source
for details.)

Furthermore i've added various boot-time options to override/tune
migration behavior.

Firstly, there's a blanket override for autodetection:

	migration_cost=1000,2000,3000

will override the depth 0/1/2 values with 1msec/2msec/3msec values.

Secondly, there's a global factor that can be used to increase (or
decrease) the autodetected values:

	migration_factor=120

will increase the autodetected values by 20%. This option is useful to
tune things in a workload-dependent way - e.g. if a workload is
cache-insensitive then CPU utilization can be maximized by specifying
migration_factor=0.

I've tested the autodetection code quite extensively on x86, on 3
P3/Xeon/2MB, and the autodetected values look pretty good:

Dual Celeron (128K L2 cache):

 ---------------------
 migration cost matrix (max_cache_size: 131072, cpu: 467 MHz):
 ---------------------
           [00]    [01]
 [00]:     -     1.7(1)
 [01]:   1.7(1)    -
 ---------------------
 cacheflush times [2]: 0.0 (0) 1.7 (1784008)
 ---------------------

Here the slow memory subsystem dominates system performance, and even
though caches are small, the migration cost is 1.7 msecs.

Dual HT P4 (512K L2 cache):

 ---------------------
 migration cost matrix (max_cache_size: 524288, cpu: 2379 MHz):
 ---------------------
           [00]    [01]    [02]    [03]
 [00]:     -     0.4(1)  0.0(0)  0.4(1)
 [01]:   0.4(1)    -     0.4(1)  0.0(0)
 [02]:   0.0(0)  0.4(1)    -     0.4(1)
 [03]:   0.4(1)  0.0(0)  0.4(1)    -
 ---------------------
 cacheflush times [2]: 0.0 (33900) 0.4 (448514)
 ---------------------

Here it can be seen that there is no migration cost between two HT
siblings (CPU#0/2 and CPU#1/3 are separate physical CPUs). A fast memory
system makes inter-physical-CPU migration pretty cheap: 0.4 msecs.

8-way P3/Xeon [2MB L2 cache]:

 ---------------------
 migration cost matrix (max_cache_size: 2097152, cpu: 700 MHz):
 ---------------------
           [00]    [01]    [02]    [03]    [04]    [05]    [06]    [07]
 [00]:     -    19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)
 [01]:  19.2(1)    -    19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)
 [02]:  19.2(1) 19.2(1)    -    19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)
 [03]:  19.2(1) 19.2(1) 19.2(1)    -    19.2(1) 19.2(1) 19.2(1) 19.2(1)
 [04]:  19.2(1) 19.2(1) 19.2(1) 19.2(1)    -    19.2(1) 19.2(1) 19.2(1)
 [05]:  19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)    -    19.2(1) 19.2(1)
 [06]:  19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)    -    19.2(1)
 [07]:  19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)    -
 ---------------------
 cacheflush times [2]: 0.0 (0) 19.2 (19281756)
 ---------------------

This one has huge caches and a relatively slow memory subsystem - so the
migration cost is 19 msecs.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Cc: <wilder@us.ibm.com>
Signed-off-by: John Hawkes <hawkes@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-12 09:08:50 -08:00
John Hawkes
9c1cfda20a [PATCH] cpusets: Move the ia64 domain setup code to the generic code
Signed-off-by: John Hawkes <hawkes@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-07 16:57:40 -07:00
Nick Piggin
687f1661d3 [PATCH] sched: sched tuning
Do some basic initial tuning.

Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-25 16:24:42 -07:00
Nick Piggin
147cbb4bbe [PATCH] sched: balance on fork
Reimplement the balance on exec balancing to be sched-domains aware.  Use this
to also do balance on fork balancing.  Make x86_64 do balance on fork over the
NUMA domain.

The problem that the non sched domains aware blancing became apparent on dual
core, multi socket opterons.  What we want is for the new tasks to be sent to
a different socket, but more often than not, we would first load up our
sibling core, or fill two cores of a single remote socket before selecting a
new one.

This gives large improvements to STREAM on such systems.

Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-25 16:24:42 -07:00
Nick Piggin
cafb20c1f9 [PATCH] sched: no aggressive idle balancing
Remove the very aggressive idle stuff that has recently gone into 2.6 - it is
going against the direction we are trying to go.  Hopefully we can regain
performance through other methods.

Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-25 16:24:42 -07:00
Nick Piggin
7897986bad [PATCH] sched: balance timers
Do CPU load averaging over a number of different intervals.  Allow each
interval to be chosen by sending a parameter to source_load and target_load.
0 is instantaneous, idx > 0 returns a decaying average with the most recent
sample weighted at 2^(idx-1).  To a maximum of 3 (could be easily increased).

So generally a higher number will result in more conservative balancing.

Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-25 16:24:41 -07:00
Linus Torvalds
1da177e4c3 Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
2005-04-16 15:20:36 -07:00