Hello,
This series is against 3.14.0-rc7.
It is amied to further improve 'percpu_ida' tags locality by taking
into account system's CPU topology when stealing tags. That is try
to steal from a CPU which is 'closest' to the stealing one.
I would not bother to post this, since on several system the change
did not show any improvement, i.e. on such one:
CPU0 attaching sched-domain:
domain 0: span 0,8 level SIBLING
groups: 0 (cpu_power = 588) 8 (cpu_power = 588)
domain 1: span 0-3,8-11 level MC
groups: 0,8 (cpu_power = 1176) 1,9 (cpu_power = 1176) 2,10 (cpu_power =
1176) 3,11 (cpu_power = 1176)
domain 2: span 0-15 level NUMA
groups: 0-3,8-11 (cpu_power = 4704) 4-7,12-15 (cpu_power = 4704)
But other systems (more dense?) showed increased cache-hit rate
up to 20%, i.e. this one:
CPU5 attaching sched-domain:
domain 0: span 0-5 level MC
groups: 5 (cpu_power = 1023) 0 (cpu_power = 1023) 1 (cpu_power = 1023) 2
(cpu_power = 1023) 3 (cpu_power = 1023) 4 (cpu_power = 1023)
domain 1: span 0-7 level NUMA
groups: 0-5 (cpu_power = 6138) 6-7 (cpu_power = 2046)
CPU6 attaching sched-domain:
domain 0: span 6-7 level MC
groups: 6 (cpu_power = 1023) 7 (cpu_power = 1023)
domain 1: span 0-7 level NUMA
groups: 6-7 (cpu_power = 2046) 0-5 (cpu_power = 6138)
I tested using 'null_blk' device with number of threads equal
to the number of CPUs with each thread affined to one CPU and
not affined, with no difference.
Suggestions are welcomed :)
Thanks!
Cc: Kent Overstreet <k...@daterainc.com>
Cc: Jens Axboe <ax...@kernel.dk>
Cc: Shaohua Li <s...@kernel.org>
Cc: Nicholas Bellinger <n...@linux-iscsi.org>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Alexander Gordeev (2):
sched: Introduce topology level masks and for_each_tlm() macro
percpu_ida: Use for_each_tlm() macro for CPU lookup in steal_tags()
include/linux/percpu_ida.h | 1 -
include/linux/sched.h | 5 ++
kernel/sched/core.c | 89 ++++++++++++++++++++++++++++++++++++++++++++
lib/percpu_ida.c | 46 +++++++++-------------
4 files changed, 113 insertions(+), 28 deletions(-)
--
1.7.7.6
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