Re: [PATCH 4/6] psi: introduce state_mask to represent stalled psi states
From: Peter Zijlstra <peterz@infradead.org>
Date: 2018-12-17 15:55:42
Also in:
cgroups, linux-mm, lkml
On Fri, Dec 14, 2018 at 09:15:06AM -0800, Suren Baghdasaryan wrote:
quoted hunk ↗ jump to hunk
The psi monitoring patches will need to determine the same states as record_times(). To avoid calculating them twice, maintain a state mask that can be consulted cheaply. Do this in a separate patch to keep the churn in the main feature patch at a minimum. Signed-off-by: Suren Baghdasaryan <surenb@google.com> --- include/linux/psi_types.h | 3 +++ kernel/sched/psi.c | 29 +++++++++++++++++++---------- 2 files changed, 22 insertions(+), 10 deletions(-)diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h index 2cf422db5d18..2c6e9b67b7eb 100644 --- a/include/linux/psi_types.h +++ b/include/linux/psi_types.h@@ -53,6 +53,9 @@ struct psi_group_cpu { /* States of the tasks belonging to this group */ unsigned int tasks[NR_PSI_TASK_COUNTS]; + /* Aggregate pressure state derived from the tasks */ + u32 state_mask; + /* Period time sampling buckets for each state of interest (ns) */ u32 times[NR_PSI_STATES];
Since we spend so much time counting space in that line, maybe add a note to the Changlog about how this fits. Also, since I just had to re-count, you might want to add explicit numbers to the psi_res and psi_states enums.
+ if (state_mask & (1 << s))
We have the BIT() macro, but I'm honestly not sure that will improve things.