Messages in this thread | | | From | Vincent Guittot <> | Date | Thu, 28 Mar 2024 17:48:46 +0100 | Subject | Re: [PATCH 1/1] sched/fair: allow disabling newidle_balance with sched_relax_domain_level |
| |
On Thu, 28 Mar 2024 at 17:27, Vitalii Bursov <vitaly@bursov.com> wrote: > > > On 28.03.24 16:43, Vincent Guittot wrote: > > On Thu, 28 Mar 2024 at 01:31, Vitalii Bursov <vitaly@bursov.com> wrote: > >> > >> Change relax_domain_level checks so that it would be possible > >> to exclude all domains from newidle balancing. > >> > >> This matches the behavior described in the documentation: > >> -1 no request. use system default or follow request of others. > >> 0 no search. > >> 1 search siblings (hyperthreads in a core). > >> > >> "2" enables levels 0 and 1, level_max excludes the last (level_max) > >> level, and level_max+1 includes all levels. > > > > I was about to say that max+1 is useless because it's the same as -1 > > but it's not exactly the same because it can supersede the system wide > > default_relax_domain_level. I wonder if one should be able to enable > > more levels than what the system has set by default. > > I don't know is such systems exist, but cpusets.rst suggests that > increasing it beyoud the default value is possible: > > If your situation is: > > > > - The migration costs between each cpu can be assumed considerably > > small(for you) due to your special application's behavior or > > special hardware support for CPU cache etc. > > - The searching cost doesn't have impact(for you) or you can make > > the searching cost enough small by managing cpuset to compact etc. > > - The latency is required even it sacrifices cache hit rate etc. > > then increasing 'sched_relax_domain_level' would benefit you.
Fair enough. The doc should be updated as we can now clear the flags but not set them
> > > >> > >> Signed-off-by: Vitalii Bursov <vitaly@bursov.com> > >> --- > >> kernel/cgroup/cpuset.c | 2 +- > >> kernel/sched/debug.c | 1 + > >> kernel/sched/topology.c | 2 +- > >> 3 files changed, 3 insertions(+), 2 deletions(-) > >> > >> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c > >> index 4237c874871..da24187c4e0 100644 > >> --- a/kernel/cgroup/cpuset.c > >> +++ b/kernel/cgroup/cpuset.c > >> @@ -2948,7 +2948,7 @@ bool current_cpuset_is_being_rebound(void) > >> static int update_relax_domain_level(struct cpuset *cs, s64 val) > >> { > >> #ifdef CONFIG_SMP > >> - if (val < -1 || val >= sched_domain_level_max) > >> + if (val < -1 || val > sched_domain_level_max + 1) > >> return -EINVAL; > >> #endif > >> > >> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c > >> index 8d5d98a5834..8454cd4e5e1 100644 > >> --- a/kernel/sched/debug.c > >> +++ b/kernel/sched/debug.c > >> @@ -423,6 +423,7 @@ static void register_sd(struct sched_domain *sd, struct dentry *parent) > >> > >> #undef SDM > >> > >> + debugfs_create_u32("level", 0444, parent, (u32 *)&sd->level); > > > > IMO, this should be a separate patch as it's not part of the fix > > Thanks, I'll split it. > > >> debugfs_create_file("flags", 0444, parent, &sd->flags, &sd_flags_fops); > >> debugfs_create_file("groups_flags", 0444, parent, &sd->groups->flags, &sd_flags_fops); > >> } > >> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > >> index 99ea5986038..3127c9b30af 100644 > >> --- a/kernel/sched/topology.c > >> +++ b/kernel/sched/topology.c > >> @@ -1468,7 +1468,7 @@ static void set_domain_attribute(struct sched_domain *sd, > >> } else > >> request = attr->relax_domain_level; > >> > >> - if (sd->level > request) { > >> + if (sd->level >= request) { > > > > good catch and worth : > > Fixes: 9ae7ab20b483 ("sched/topology: Don't set SD_BALANCE_WAKE on > > cpuset domain relax") > > > Will add this. > Thanks. > > > > >> /* Turn off idle balance on this domain: */ > >> sd->flags &= ~(SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE); > >> } > >> -- > >> 2.20.1 > >>
| |