Commit c7ce813f authored by Kent Overstreet's avatar Kent Overstreet Committed by Kent Overstreet
Browse files

bcachefs: Add a tracepoint for the btree cache shrinker 



This is to help with diagnosing why the btree node can doesn't seem to
be shrinking - we've had issues in the past with granularity/batch size,
since btree nodes are so big.

Signed-off-by: default avatarKent Overstreet <kent.overstreet@gmail.com>
parent d93cf685

fs/bcachefs/btree_cache.c

+9 −2
Original line number Diff line number Diff line
@@ -275,6 +275,7 @@ static unsigned long bch2_btree_cache_scan(struct shrinker *shrink, 
	unsigned long touched = 0;

	unsigned long freed = 0;

	unsigned i, flags;

	unsigned long ret = SHRINK_STOP;



	if (bch2_btree_shrinker_disabled)

		return SHRINK_STOP;
@@ -283,7 +284,7 @@ static unsigned long bch2_btree_cache_scan(struct shrinker *shrink, 
	if (sc->gfp_mask & __GFP_FS)

		mutex_lock(&bc->lock);

	else if (!mutex_trylock(&bc->lock))

		return -1;

		goto out_norestore;



	flags = memalloc_nofs_save();
@@ -358,8 +359,14 @@ static unsigned long bch2_btree_cache_scan(struct shrinker *shrink, 


	mutex_unlock(&bc->lock);

out:

	ret = (unsigned long) freed * btree_pages(c);

	memalloc_nofs_restore(flags);

	return (unsigned long) freed * btree_pages(c);

out_norestore:

	trace_btree_cache_scan(sc->nr_to_scan,

			       sc->nr_to_scan / btree_pages(c),

			       btree_cache_can_free(bc),

			       ret);

	return ret;

}



static unsigned long bch2_btree_cache_count(struct shrinker *shrink,

fs/bcachefs/trace.h

+28 −0
Original line number Diff line number Diff line
@@ -318,6 +318,34 @@ DEFINE_EVENT(btree_node, btree_set_root, 
	TP_ARGS(c, b)

);



TRACE_EVENT(btree_cache_scan,

	TP_PROTO(unsigned long nr_to_scan_pages,

		 unsigned long nr_to_scan_nodes,

		 unsigned long can_free_nodes,

		 long ret),

	TP_ARGS(nr_to_scan_pages, nr_to_scan_nodes, can_free_nodes, ret),



	TP_STRUCT__entry(

		__field(unsigned long,	nr_to_scan_pages	)

		__field(unsigned long,	nr_to_scan_nodes	)

		__field(unsigned long,	can_free_nodes		)

		__field(long,		ret			)

	),



	TP_fast_assign(

		__entry->nr_to_scan_pages	= nr_to_scan_pages;

		__entry->nr_to_scan_nodes	= nr_to_scan_nodes;

		__entry->can_free_nodes		= can_free_nodes;

		__entry->ret			= ret;

	),



	TP_printk("scanned for %lu pages, %lu nodes, can free %lu nodes, ret %li",

		  __entry->nr_to_scan_pages,

		  __entry->nr_to_scan_nodes,

		  __entry->can_free_nodes,

		  __entry->ret)

);



/* Garbage collection */



DEFINE_EVENT(btree_node, btree_gc_rewrite_node,