From ab82e57981d0e4cb46d2817e7b65b9d5fdcf3832 Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Tue, 4 Mar 2025 13:19:05 -0800 Subject: [PATCH] mm/damon/core: introduce damos->ops_filters Patch series "mm/damon: make allow filters after reject filters useful and intuitive". DAMOS filters do allow or reject elements of memory for given DAMOS scheme only if those match the filter criterias. For elements that don't match any DAMOS filter, 'allowing' is the default behavior. This makes allow-filters that don't have any reject-filter after them meaningless sources of overhead. The decision was made to keep the behavior consistent with that before the introduction of allow-filters. This, however, makes usage of DAMOS filters confusing and inefficient. It is more intuitive and still consistent behavior to reject by default unless there is no filter at all or the last filter is a reject filter. Update the filtering logic in the way and update documents to clarify the behavior. Note that this is changing the old behavior. But the old behavior for the problematic filter combination was definitely confusing, inefficient and anyway useless. Also, the behavior has relatively recently introduced. It is difficult to anticipate any user that depends on the behavior. Hence this is not a user-breaking behavior change but an obvious improvement. This patch (of 9): DAMOS filters can be categorized into two groups depending on which layer they are handled, namely core layer and ops layer. The groups are important because the filtering behavior depends on evaluation sequence of filters, and core layer-handled filters are evaluated before operations layer-handled ones. The behavior is clearly documented, but the implementation is bit inefficient and complicated. All filters are maintained in a single list (damos->filters) in mix. Filters evaluation logics in core layer and operations layer iterates all the filters on the list, while skipping filters that should be not handled by the layer of the logic. It is inefficient. Making future extensions having differentiations for filters of different handling layers will also be complicated. Add a new list that will be used for having all operations layer-handled DAMOS filters to DAMOS scheme data structure. Also add the support of its initialization and basic traversal functions. Link: https://lkml.kernel.org/r/20250304211913.53574-1-sj@kernel.org Link: https://lkml.kernel.org/r/20250304211913.53574-2-sj@kernel.org Signed-off-by: SeongJae Park Cc: Jonathan Corbet Cc: SeongJae Park Signed-off-by: Andrew Morton --- include/linux/damon.h | 8 ++++++++ mm/damon/core.c | 1 + 2 files changed, 9 insertions(+) diff --git a/include/linux/damon.h b/include/linux/damon.h index b3e2c793c1f4..7f76e2e99f37 100644 --- a/include/linux/damon.h +++ b/include/linux/damon.h @@ -448,6 +448,7 @@ struct damos_access_pattern { * @wmarks: Watermarks for automated (in)activation of this scheme. * @target_nid: Destination node if @action is "migrate_{hot,cold}". * @filters: Additional set of &struct damos_filter for &action. + * @ops_filters: ops layer handling &struct damos_filter objects list. * @last_applied: Last @action applied ops-managing entity. * @stat: Statistics of this scheme. * @list: List head for siblings. @@ -508,6 +509,7 @@ struct damos { int target_nid; }; struct list_head filters; + struct list_head ops_filters; void *last_applied; struct damos_stat stat; struct list_head list; @@ -858,6 +860,12 @@ static inline unsigned long damon_sz_region(struct damon_region *r) #define damos_for_each_filter_safe(f, next, scheme) \ list_for_each_entry_safe(f, next, &(scheme)->filters, list) +#define damos_for_each_ops_filter(f, scheme) \ + list_for_each_entry(f, &(scheme)->ops_filters, list) + +#define damos_for_each_ops_filter_safe(f, next, scheme) \ + list_for_each_entry_safe(f, next, &(scheme)->ops_filters, list) + #ifdef CONFIG_DAMON struct damon_region *damon_new_region(unsigned long start, unsigned long end); diff --git a/mm/damon/core.c b/mm/damon/core.c index 9d37d3664030..5415b7603d01 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -375,6 +375,7 @@ struct damos *damon_new_scheme(struct damos_access_pattern *pattern, scheme->next_apply_sis = 0; scheme->walk_completed = false; INIT_LIST_HEAD(&scheme->filters); + INIT_LIST_HEAD(&scheme->ops_filters); scheme->stat = (struct damos_stat){}; INIT_LIST_HEAD(&scheme->list); -- 2.25.1