linux/include
Peter Zijlstra 0f004f5a69 sched: Cure more NO_HZ load average woes
There's a long-running regression that proved difficult to fix and
which is hitting certain people and is rather annoying in its effects.

Damien reported that after 74f5187ac8 (sched: Cure load average vs
NO_HZ woes) his load average is unnaturally high, he also noted that
even with that patch reverted the load avgerage numbers are not
correct.

The problem is that the previous patch only solved half the NO_HZ
problem, it addressed the part of going into NO_HZ mode, not of
comming out of NO_HZ mode. This patch implements that missing half.

When comming out of NO_HZ mode there are two important things to take
care of:

 - Folding the pending idle delta into the global active count.
 - Correctly aging the averages for the idle-duration.

So with this patch the NO_HZ interaction should be complete and
behaviour between CONFIG_NO_HZ=[yn] should be equivalent.

Furthermore, this patch slightly changes the load average computation
by adding a rounding term to the fixed point multiplication.

Reported-by: Damien Wyart <damien.wyart@free.fr>
Reported-by: Tim McGrath <tmhikaru@gmail.com>
Tested-by: Damien Wyart <damien.wyart@free.fr>
Tested-by: Orion Poplawski <orion@cora.nwra.com>
Tested-by: Kyle McMartin <kyle@mcmartin.ca>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@kernel.org
Cc: Chase Douglas <chase.douglas@canonical.com>
LKML-Reference: <1291129145.32004.874.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-12-08 20:15:04 +01:00
..
acpi
asm-generic
crypto
drm drm/i915: announce to userspace that the bsd ring is coherent 2010-12-05 10:40:39 +00:00
keys
linux sched: Cure more NO_HZ load average woes 2010-12-08 20:15:04 +01:00
math-emu
media [media] v4l: Remove module_name argument to the v4l2_i2c_new_subdev* functions 2010-11-22 11:56:26 -02:00
mtd
net af_unix: limit recursion level 2010-11-29 09:45:15 -08:00
pcmcia
rdma
rxrpc
scsi SCSI host lock push-down 2010-11-16 13:33:23 -08:00
sound ARM: mach-shmobile: ap4evb: FSI clock use proper process for HDMI 2010-11-24 15:29:56 +09:00
trace
video fbdev: da8xx: punt duplicated FBIO_WAITFORVSYNC define 2010-11-16 10:14:22 +09:00
xen xen: fix MSI setup and teardown for PV on HVM guests 2010-12-02 14:34:25 +00:00
Kbuild