> -----Original Message----- > From: Valentin Schneider [mailto:valentin.schnei...@arm.com] > Sent: Thursday, February 4, 2021 4:55 AM > To: linux-kernel@vger.kernel.org > Cc: vincent.guit...@linaro.org; mgor...@suse.de; mi...@kernel.org; > pet...@infradead.org; dietmar.eggem...@arm.com; morten.rasmus...@arm.com; > linux...@openeuler.org; xuwei (O) <xuw...@huawei.com>; Liguozhu (Kenneth) > <liguo...@hisilicon.com>; tiantao (H) <tiant...@hisilicon.com>; wanghuiqiang > <wanghuiqi...@huawei.com>; Zengtao (B) <prime.z...@hisilicon.com>; Jonathan > Cameron <jonathan.came...@huawei.com>; guodong...@linaro.org; Song Bao Hua > (Barry Song) <song.bao....@hisilicon.com>; Meelis Roos <mr...@linux.ee> > Subject: [RFC PATCH 2/2] Revert "sched/topology: Warn when NUMA diameter > 2" > > The scheduler topology code can now figure out what to do with such > topologies. > > This reverts commit b5b217346de85ed1b03fdecd5c5076b34fbb2f0b. > > Signed-off-by: Valentin Schneider <valentin.schnei...@arm.com> Yes, this is fine. I actually have seen some other problems we need to consider. The current code is probably well consolidated for machines with 2 hops or less. Thus, even after we fix the 3-hops span issue, I can still see some other issue. For example, if we change the sd flags and remove the SD_BALANCE flags for the last hops in sd_init(), we are able to see large score increase in unixbench. if (sched_domains_numa_distance[tl->numa_level] > node_reclaim_distance || is_3rd_hops_domain(...)) { sd->flags &= ~(SD_BALANCE_EXEC | SD_BALANCE_FORK | SD_WAKE_AFFINE); } So guess something needs to be tuned for machines with 3 hops or more. But we need a kernel which has the fix of 3-hops issue before we can do more work. > --- > kernel/sched/topology.c | 33 --------------------------------- > 1 file changed, 33 deletions(-) > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index a8f69f234258..0fa41aab74e0 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -688,7 +688,6 @@ cpu_attach_domain(struct sched_domain *sd, struct > root_domain *rd, int cpu) > { > struct rq *rq = cpu_rq(cpu); > struct sched_domain *tmp; > - int numa_distance = 0; > > /* Remove the sched domains which do not contribute to scheduling. */ > for (tmp = sd; tmp; ) { > @@ -720,38 +719,6 @@ cpu_attach_domain(struct sched_domain *sd, struct > root_domain *rd, int cpu) > sd->child = NULL; > } > > - for (tmp = sd; tmp; tmp = tmp->parent) > - numa_distance += !!(tmp->flags & SD_NUMA); > - > - /* > - * FIXME: Diameter >=3 is misrepresented. > - * > - * Smallest diameter=3 topology is: > - * > - * node 0 1 2 3 > - * 0: 10 20 30 40 > - * 1: 20 10 20 30 > - * 2: 30 20 10 20 > - * 3: 40 30 20 10 > - * > - * 0 --- 1 --- 2 --- 3 > - * > - * NUMA-3 0-3 N/A N/A 0-3 > - * groups: {0-2},{1-3} > {1-3},{0-2} > - * > - * NUMA-2 0-2 0-3 0-3 1-3 > - * groups: {0-1},{1-3} {0-2},{2-3} {1-3},{0-1} > {2-3},{0-2} > - * > - * NUMA-1 0-1 0-2 1-3 2-3 > - * groups: {0},{1} {1},{2},{0} {2},{3},{1} {3},{2} > - * > - * NUMA-0 0 1 2 3 > - * > - * The NUMA-2 groups for nodes 0 and 3 are obviously buggered, as the > - * group span isn't a subset of the domain span. > - */ > - WARN_ONCE(numa_distance > 2, "Shortest NUMA path spans too many > nodes\n"); > - > sched_domain_debug(sd, cpu); > > rq_attach_root(rq, rd); > -- > 2.27.0 Thanks Barry
