From 7d7e02563bcd5cebc18c92cf0882bcc7bb9c8809 Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Fri, 10 Dec 2021 14:46:25 -0800 Subject: [PATCH] mm/damon/core: fix fake load reports due to uninterruptible sleeps commit 70e9274805fccfd175d0431a947bfd11ee7df40e upstream. Because DAMON sleeps in uninterruptible mode, /proc/loadavg reports fake load while DAMON is turned on, though it is doing nothing. This can confuse users[1]. To avoid the case, this commit makes DAMON sleeps in idle mode. [1] https://lore.kernel.org/all/11868371.O9o76ZdvQC@natalenko.name/ Link: https://lkml.kernel.org/r/20211126145015.15862-3-sj@kernel.org Fixes: 2224d8485492 ("mm: introduce Data Access MONitor (DAMON)") Reported-by: Oleksandr Natalenko Signed-off-by: SeongJae Park Tested-by: Oleksandr Natalenko Cc: John Stultz Cc: Thomas Gleixner Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/damon/core.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 30e9211..7a4912d 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -357,6 +357,15 @@ int damon_start(struct damon_ctx **ctxs, int nr_ctxs) return err; } +static void kdamond_usleep(unsigned long usecs) +{ + /* See Documentation/timers/timers-howto.rst for the thresholds */ + if (usecs > 20 * 1000) + schedule_timeout_idle(usecs_to_jiffies(usecs)); + else + usleep_idle_range(usecs, usecs + 1); +} + /* * __damon_stop() - Stops monitoring of given context. * @ctx: monitoring context @@ -370,8 +379,7 @@ static int __damon_stop(struct damon_ctx *ctx) ctx->kdamond_stop = true; mutex_unlock(&ctx->kdamond_lock); while (damon_kdamond_running(ctx)) - usleep_range(ctx->sample_interval, - ctx->sample_interval * 2); + kdamond_usleep(ctx->sample_interval); return 0; } mutex_unlock(&ctx->kdamond_lock); @@ -670,7 +678,7 @@ static int kdamond_fn(void *data) ctx->callback.after_sampling(ctx)) set_kdamond_stop(ctx); - usleep_range(ctx->sample_interval, ctx->sample_interval + 1); + kdamond_usleep(ctx->sample_interval); if (ctx->primitive.check_accesses) max_nr_accesses = ctx->primitive.check_accesses(ctx); -- 2.7.4