linux-kernel - [tg_shares_up rewrite v3 00/11] reduce overhead for tg->shares distribution

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Message-Id: <20101112032405.657789056@google.com>
Date:	Thu, 11 Nov 2010 19:24:05 -0800
From:	Paul Turner <pjt@...gle.com>
To:	linux-kernel@...r.kernel.org
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Chris Friesen <cfriesen@...tel.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Pierre Bourdon <pbourdon@...ellency.fr>,
	Paul Turner <pjt@...gle.com>,
	Bharata B Rao <bharata@...ux.vnet.ibm.com>,
	Karl Rister <kmr@...ibm.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	David Miller <davem@...emloft.net>
Subject: [tg_shares_up rewrite v3 00/11] reduce overhead for tg->shares distribution

-- 

This is v3 of the tg_shares_up re-write previously posted at:
http://lkml.org/lkml/2010/10/16/17

It corrects compile errors in the !CONFIG_FAIR_GROUP_SCHED present in v2 posted
yesterday (Thanks to David Miller for catching this) as well as a race in the
destruction of a task_group.
http://lkml.org/lkml/2010/11/10/618

The key idea behind this patchset is an idea of Peter Zijlstra'a to compute
global loads as a function of local averages, avoiding the cpu-cpu interactions
which previously plagued tg_shares_up.

Not much 'material' has changed since v1 since results seem favourable/stable.

Changes:
v3
sched-rework-tg_shares_up.patch
- remove lint: {max,min}_sched_shares_ratelimit from sysctl.c 

sched-tg-ondemand.patch
- (bug fix) fix synchronization on leaf_cfs_rq_list removal during task_group reclaim.
- fix !CONFIG_FAIR_GROUP_SCHED build 
- fix comment on what task_group_lock protects

sched-tg-global_update_load.patch
- add missing arguments to update_cfs_load() in !CONFIG_FAIR_GROUP_SCHED case

v2 (http://lkml.org/lkml/2010/11/10/618)
sched-rework-tg_shares_up.patch
- (bug fix) use owning tg->shares value in effective_load
- remove redundant cfs_rq_of() in {enqueue,dequeue}_entity

sched-tg-add-shares_window_sysctl.patch
- update comment on sysctl interpretation

sched-tg-fix-update_cfs_load.patch
- update comment to reflect periods instead of foldings (more intuitive)

Some motivation again:
24 thread Intel box, 150 active cgroups, multiple threads/group, system load at ~90% (sample size=10s):
tip:
    2.64%  [k] tg_shares_up <!>
    0.15%  [k] __set_se_shares

patched:
    0.02%  [k] update_cfs_load
    0.01%  [k] update_cpu_load
    0.00%  [k] update_cfs_shares

Fairness coverage for the above at: http://rs5.risingnet.net/~pjt/patches/shares_data_v1.txt

Thanks,

- Paul

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