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Patch series "memcg, cpuisol: do not interfere pcp cache charges draining with cpuisol workloads". Leonardo has reported [1] that pcp memcg charge draining can interfere with cpu isolated workloads. The said draining is done from a WQ context with a pcp worker scheduled on each CPU which holds any cached charges for a specific memcg hierarchy. Operation is not really a common operation [2]. It can be triggered from the userspace though so some care is definitely due. Leonardo has tried to address the issue by allowing remote charge draining [3]. This approach requires an additional locking to synchronize pcp caches sync from a remote cpu from local pcp consumers. Even though the proposed lock was per-cpu there is still potential for contention and less predictable behavior. This patchset addresses the issue from a different angle. Rather than dealing with a potential synchronization, cpus which are isolated are simply never scheduled to be drained. This means that a small amount of charges could be laying around and waiting for a later use or they are flushed when a different memcg is charged from the same cpu. More details are in patch 2. The first patch from Frederic is implementing an abstraction to tell whether a specific cpu has been isolated and therefore require a special treatment. This patch (of 2): Provide this new API to check if a CPU has been isolated either through isolcpus= or nohz_full= kernel parameter. It aims at avoiding kernel load deemed to be safely spared on CPUs running sensitive workload that can't bear any disturbance, such as pcp cache draining. Link: https://lkml.kernel.org/r/20230317134448.11082-1-mhocko@kernel.org Link: https://lkml.kernel.org/r/20230317134448.11082-2-mhocko@kernel.org Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Michal Hocko <mhocko@suse.com> Suggested-by: Michal Hocko <mhocko@suse.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Shakeel Butt <shakeelb@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Leonardo Bras <leobras@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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.. | ||
affinity.h | ||
autogroup.h | ||
clock.h | ||
cond_resched.h | ||
coredump.h | ||
cpufreq.h | ||
cputime.h | ||
deadline.h | ||
debug.h | ||
hotplug.h | ||
idle.h | ||
init.h | ||
isolation.h | ||
jobctl.h | ||
loadavg.h | ||
mm.h | ||
nohz.h | ||
numa_balancing.h | ||
posix-timers.h | ||
prio.h | ||
rseq_api.h | ||
rt.h | ||
sd_flags.h | ||
signal.h | ||
smt.h | ||
stat.h | ||
sysctl.h | ||
task.h | ||
task_flags.h | ||
task_stack.h | ||
thread_info_api.h | ||
topology.h | ||
types.h | ||
user.h | ||
wake_q.h | ||
xacct.h |