From: SeongJae Park Date: Tue, 16 Sep 2025 18:31:26 +0000 (-0700) Subject: mm/damon/stat: expose the current tuned aggregation interval X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=cc7ceb1d14b0a6f6eb83dfdfa91970f69c4c23b4;p=thirdparty%2Fkernel%2Fstable.git mm/damon/stat: expose the current tuned aggregation interval Patch series "mm/damon/stat: expose auto-tuned intervals and non-idle ages". DAMON_STAT is intentionally providing limited information for easy consumption of the information. From production fleet level usages, below limitations are found, though. The aggregation interval of DAMON_STAT represents the granularity of the memory_idle_ms_percentiles. But the interval is auto-tuned and not exposed to users, so users cannot know the granularity. All memory regions of non-zero (positive) nr_accesses are treated as having zero idle time. A significant portion of production systems have such zero idle time. Hence breakdown of warm and hot data is nearly impossible. Make following changes to overcome the limitations. Expose the auto-tuned aggregation interval with a new parameter named aggr_interval_us. Expose the age of non-zero nr_accesses (how long >0 access frequency the region retained) regions as a negative idle time. This patch (of 2): DAMON_STAT calculates the idle time for a region as the region's age multiplied by the aggregation interval. That is, the aggregation interval is the granularity of the idle time. Since the aggregation interval is auto-tuned and not exposed to users, however, users cannot easily know in what granularity the stat is made. Expose the tuned aggregation interval in microseconds via a new parameter, aggr_interval_us. Link: https://lkml.kernel.org/r/20250916183127.65708-1-sj@kernel.org Link: https://lkml.kernel.org/r/20250916183127.65708-2-sj@kernel.org Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton --- diff --git a/mm/damon/stat.c b/mm/damon/stat.c index c4fbd8cfa5eb6..1a8465abef4ab 100644 --- a/mm/damon/stat.c +++ b/mm/damon/stat.c @@ -39,6 +39,11 @@ module_param_array(memory_idle_ms_percentiles, ulong, NULL, 0400); MODULE_PARM_DESC(memory_idle_ms_percentiles, "Memory idle time percentiles in milliseconds"); +static unsigned long aggr_interval_us; +module_param(aggr_interval_us, ulong, 0400); +MODULE_PARM_DESC(aggr_interval_us, + "Current tuned aggregation interval in microseconds"); + static struct damon_ctx *damon_stat_context; static void damon_stat_set_estimated_memory_bandwidth(struct damon_ctx *c) @@ -133,6 +138,7 @@ static int damon_stat_damon_call_fn(void *data) return 0; last_refresh_jiffies = jiffies; + aggr_interval_us = c->attrs.aggr_interval; damon_stat_set_estimated_memory_bandwidth(c); damon_stat_set_idletime_percentiles(c); return 0;