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author | Peter Zijlstra <peterz@infradead.org> | 2016-06-24 16:11:02 +0200 |
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committer | Ingo Molnar <mingo@kernel.org> | 2016-06-27 11:18:37 +0200 |
commit | ea1dc6fc6242f991656e35e2ed3d90ec1cd13418 (patch) | |
tree | 3a4091a59bdf94e432e1c0f7549b692e15e7e01f /arch/x86/kernel/amd_nb.c | |
parent | 7dd4912594daf769a46744848b05bd5bc6d62469 (diff) | |
download | linux-stable-ea1dc6fc6242f991656e35e2ed3d90ec1cd13418.tar.gz linux-stable-ea1dc6fc6242f991656e35e2ed3d90ec1cd13418.tar.bz2 linux-stable-ea1dc6fc6242f991656e35e2ed3d90ec1cd13418.zip |
sched/fair: Fix calc_cfs_shares() fixed point arithmetics width confusion
Commit:
fde7d22e01aa ("sched/fair: Fix overly small weight for interactive group entities")
did something non-obvious but also did it buggy yet latent.
The problem was exposed for real by a later commit in the v4.7 merge window:
2159197d6677 ("sched/core: Enable increased load resolution on 64-bit kernels")
... after which tg->load_avg and cfs_rq->load.weight had different
units (10 bit fixed point and 20 bit fixed point resp.).
Add a comment to explain the use of cfs_rq->load.weight over the
'natural' cfs_rq->avg.load_avg and add scale_load_down() to correct
for the difference in unit.
Since this is (now, as per a previous commit) the only user of
calc_tg_weight(), collapse it.
The effects of this bug should be randomly inconsistent SMP-balancing
of cgroups workloads.
Reported-by: Jirka Hladky <jhladky@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 2159197d6677 ("sched/core: Enable increased load resolution on 64-bit kernels")
Fixes: fde7d22e01aa ("sched/fair: Fix overly small weight for interactive group entities")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/amd_nb.c')
0 files changed, 0 insertions, 0 deletions