On 8/5/21 6:00 PM, Mel Gorman wrote: > From: Ingo Molnar <mingo@xxxxxxx> > > Disable preemption on -RT for the vmstat code. On vanila the code runs > in IRQ-off regions while on -RT it may not when stats are updated under > a local_lock. "preempt_disable" ensures that the same resources is not > updated in parallel due to preemption. > > This patch differs from the preempt-rt version where __count_vm_event and > __count_vm_events are also protected. The counters are explicitly "allowed > to be to be racy" so there is no need to protect them from preemption. Only > the accurate page stats that are updated by a read-modify-write need > protection. This patch also differs in that a preempt_[en|dis]able_rt > helper is not used. As vmstat is the only user of the helper, it was > suggested that it be open-coded in vmstat.c instead of risking the helper > being used in unnecessary contexts. > > Signed-off-by: Ingo Molnar <mingo@xxxxxxx> > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
