Commit-ID: ed4ad1ca08a53cf1a805478678d1e7ff0d2cf251
Gitweb: https://git.kernel.org/tip/ed4ad1ca08a53cf1a805478678d1e7ff0d2cf251
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Mon, 2 Oct 2017 14:50:33 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 10 Oct 2017 11:45:27 +0200
sched/topology: Restore SD_PREFER_SIBLING on MC domains
The normal x86_topology on NHM+ machines degenerates because the MC
and CPU domains are of the same size, therefore MC inherits
SD_PREFER_SIBLING from CPU (which then gets taken out). The result is
that we'll spread tasks across the first NUMA level in order to
maximize cache utilization.
However, for the x86_numa_in_package_topology we loose the CPU domain,
and we'll not have SD_PREFER_SIBLING set anywhere, giving a distinct
difference in behaviour.
Commit:
8e7fbcbc22c1 ("sched: Remove stale power aware scheduling remnants and dysfunctional knobs")
made a fail by not preserving the SD_PREFER_SIBLING for the !power_saving
case on both CPU and MC.
Then commit:
6956dc568f34 ("sched/numa: Add SD_PERFER_SIBLING to CPU domain")
adds it back to the CPU but not MC.
Restore that now, such that we get consistent spreading behaviour wrt
L3 and NUMA.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/topology.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index f1cf4f3..86e81f06 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -1157,6 +1157,7 @@ sd_init(struct sched_domain_topology_level *tl,
sd->smt_gain = 1178; /* ~15% */
} else if (sd->flags & SD_SHARE_PKG_RESOURCES) {
+ sd->flags |= SD_PREFER_SIBLING;
sd->imbalance_pct = 117;
sd->cache_nice_tries = 1;
sd->busy_idx = 2;
--
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