Merge branch 'page_pool-stats'

Joe Damato says:

====================
page_pool: Add stats counters

Greetings:

Welcome to v9.

This revisions adds a commit which updates the page_pool documentation to
describe the stats API, structures, and fields.

Additionally, this revision contains a minor cosmetic change suggested by
Saeed in page_pool_recycle_in_ring in commit 2: "page_pool: Add recycle
stats", which removes an unnecessary #ifdef.

There are no functional changes in this revision.

Benchmark output from the v7 cover [1] is pasted below, as it is still
relevant since no functional changes have been made in this revision:

Benchmarks have been re-run. As always, results between runs are highly
variable; you'll find results showing that stats disabled are both faster
and slower than stats enabled in back to back benchmark runs.

Raw benchmark output with stats off [2] and stats on [3] are available for
examination.

Test system:
	- 2x Intel(R) Xeon(R) Gold 6140 CPU @ 2.30GHz
	- 2 NUMA zones, with 18 cores per zone and 2 threads per core

bench_page_pool_simple results, loops=200000000
test name			stats enabled		stats disabled
				cycles	nanosec		cycles	nanosec

for_loop			0	0.335		0	0.336
atomic_inc 			14	6.106		13	6.022
lock				30	13.365		32	13.968

no-softirq-page_pool01		75	32.884		74	32.308
no-softirq-page_pool02		79	34.696		74	32.302
no-softirq-page_pool03		110	48.005		105	46.073

tasklet_page_pool01_fast_path	14	6.156		14	6.211
tasklet_page_pool02_ptr_ring	41	18.028		39	17.391
tasklet_page_pool03_slow	107	46.646		105	46.123

bench_page_pool_cross_cpu results, loops=20000000 returning_cpus=4:
test name			stats enabled		stats disabled
				cycles	nanosec		cycles	nanosec

page_pool_cross_cpu CPU(0)	3973	1731.596	4015	1750.015
page_pool_cross_cpu CPU(1)	3976	1733.217	4022	1752.864
page_pool_cross_cpu CPU(2)	3973	1731.615	4016	1750.433
page_pool_cross_cpu CPU(3)	3976	1733.218	4021	1752.806
page_pool_cross_cpu CPU(4)	994	433.305		1005	438.217

page_pool_cross_cpu average	3378	-		3415	-

bench_page_pool_cross_cpu results, loops=20000000 returning_cpus=8:
test name			stats enabled		stats disabled
				cycles	nanosec		cycles	nanosec

page_pool_cross_cpu CPU(0)	6969	3037.488	6909	3011.463
page_pool_cross_cpu CPU(1)	6974	3039.469	6913	3012.961
page_pool_cross_cpu CPU(2)	6969	3037.575	6910	3011.585
page_pool_cross_cpu CPU(3)	6974	3039.415	6913	3012.961
page_pool_cross_cpu CPU(4)	6969	3037.288	6909	3011.368
page_pool_cross_cpu CPU(5)	6972	3038.732	6913	3012.920
page_pool_cross_cpu CPU(6)	6969	3037.350	6909	3011.386
page_pool_cross_cpu CPU(7)	6973	3039.356	6913	3012.921
page_pool_cross_cpu CPU(8)	871	379.934		864	376.620

page_pool_cross_cpu average	6293	-		6239	-

Thanks.

[1]: https://lore.kernel.org/all/1645810914-35485-1-git-send-email-jdamato@fastly.com/
[2]: https://gist.githubusercontent.com/jdamato-fsly/d7c34b9fa7be1ce132a266b0f2b92aea/raw/327dcd71d11ece10238fbf19e0472afbcbf22fd4/v7_stats_disabled
[3]: https://gist.githubusercontent.com/jdamato-fsly/d7c34b9fa7be1ce132a266b0f2b92aea/raw/327dcd71d11ece10238fbf19e0472afbcbf22fd4/v7_stats_enabled

v8 -> v9:
	- Add documentation about the page_pool_get_stats API, stats
	  structures, and fields to Documentation/networking/page_pool.rst.
	- Remove unnecessary #ifdef in page_pool_recycle_in_ring.

v7 -> v8:
	- Rename mlx5 ethtool stats so that users have a better idea of
	  their meaning.

v6 -> v7:
	- stats split out into two structs one single per-page pool struct
	  for allocation path stats and one per-cpu pointer for recycle
	  path stats.
	- page_pool_get_stats updated to use a wrapper struct to gather
	  stats for allocation and recycle stats with a single argument.
	- placement of structs adjusted
	- mlx5 driver modified to use page_pool_get_stats API

v5 -> v6:
	- Per cpu page_pool_stats struct pointer is now marked as
	  ____cacheline_aligned_in_smp. Placement of the field in the
	  struct is unchanged; it is the last field.

v4 -> v5:
	- Fixed the description of the kernel option in Kconfig.
	- Squashed commits 1-10 from v4 into a single commit for easier
	  review.
	- Changed the comment style of the comment for
	  the this_cpu_inc_alloc_stat macro.
	- Changed the return type of page_pool_get_stats from struct
	  page_pool_stat * to bool.

v3 -> v4:
	- Restructured stats to be per-cpu per-pool.
	- Global stats and proc file were removed.
	- Exposed an API (page_pool_get_stats) for batching the pool stats.

v2 -> v3:
	- patch 8/10 ("Add stat tracking cache refill") fixed placement of
	  counter increment.
	- patch 10/10 ("net-procfs: Show page pool stats in proc") updated:
		- fix unused label warning from kernel test robot,
		- fixed page_pool_seq_show to only display the refill stat
		  once,
		- added a remove_proc_entry for page_pool_stat to
		  dev_proc_net_exit.

v1 -> v2:
	- A new kernel config option has been added, which defaults to N,
	   preventing this code from being compiled in by default
	- The stats structure has been converted to a per-cpu structure
	- The stats are now exported via proc (/proc/net/page_pool_stat)
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 73 insertions, 6 deletions

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index e25d359d84d9..1943c0f0307d 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -26,6 +26,45 @@
 
 #define BIAS_MAX	LONG_MAX
 
+#ifdef CONFIG_PAGE_POOL_STATS
+/* alloc_stat_inc is intended to be used in softirq context */
+#define alloc_stat_inc(pool, __stat)	(pool->alloc_stats.__stat++)
+/* recycle_stat_inc is safe to use when preemption is possible. */
+#define recycle_stat_inc(pool, __stat)							\
+	do {										\
+		struct page_pool_recycle_stats __percpu *s = pool->recycle_stats;	\
+		this_cpu_inc(s->__stat);						\
+	} while (0)
+
+bool page_pool_get_stats(struct page_pool *pool,
+			 struct page_pool_stats *stats)
+{
+	int cpu = 0;
+
+	if (!stats)
+		return false;
+
+	memcpy(&stats->alloc_stats, &pool->alloc_stats, sizeof(pool->alloc_stats));
+
+	for_each_possible_cpu(cpu) {
+		const struct page_pool_recycle_stats *pcpu =
+			per_cpu_ptr(pool->recycle_stats, cpu);
+
+		stats->recycle_stats.cached += pcpu->cached;
+		stats->recycle_stats.cache_full += pcpu->cache_full;
+		stats->recycle_stats.ring += pcpu->ring;
+		stats->recycle_stats.ring_full += pcpu->ring_full;
+		stats->recycle_stats.released_refcnt += pcpu->released_refcnt;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL(page_pool_get_stats);
+#else
+#define alloc_stat_inc(pool, __stat)
+#define recycle_stat_inc(pool, __stat)
+#endif
+
 static int page_pool_init(struct page_pool *pool,
 			  const struct page_pool_params *params)
 {
@@ -73,6 +112,12 @@ static int page_pool_init(struct page_pool *pool,
 	    pool->p.flags & PP_FLAG_PAGE_FRAG)
 		return -EINVAL;
 
+#ifdef CONFIG_PAGE_POOL_STATS
+	pool->recycle_stats = alloc_percpu(struct page_pool_recycle_stats);
+	if (!pool->recycle_stats)
+		return -ENOMEM;
+#endif
+
 	if (ptr_ring_init(&pool->ring, ring_qsize, GFP_KERNEL) < 0)
 		return -ENOMEM;
 
@@ -117,8 +162,10 @@ static struct page *page_pool_refill_alloc_cache(struct page_pool *pool)
 	int pref_nid; /* preferred NUMA node */
 
 	/* Quicker fallback, avoid locks when ring is empty */
-	if (__ptr_ring_empty(r))
+	if (__ptr_ring_empty(r)) {
+		alloc_stat_inc(pool, empty);
 		return NULL;
+	}
 
 	/* Softirq guarantee CPU and thus NUMA node is stable. This,
 	 * assumes CPU refilling driver RX-ring will also run RX-NAPI.
@@ -145,14 +192,17 @@ static struct page *page_pool_refill_alloc_cache(struct page_pool *pool)
 			 * This limit stress on page buddy alloactor.
 			 */
 			page_pool_return_page(pool, page);
+			alloc_stat_inc(pool, waive);
 			page = NULL;
 			break;
 		}
 	} while (pool->alloc.count < PP_ALLOC_CACHE_REFILL);
 
 	/* Return last page */
-	if (likely(pool->alloc.count > 0))
+	if (likely(pool->alloc.count > 0)) {
 		page = pool->alloc.cache[--pool->alloc.count];
+		alloc_stat_inc(pool, refill);
+	}
 
 	return page;
 }
@@ -166,6 +216,7 @@ static struct page *__page_pool_get_cached(struct page_pool *pool)
 	if (likely(pool->alloc.count)) {
 		/* Fast-path */
 		page = pool->alloc.cache[--pool->alloc.count];
+		alloc_stat_inc(pool, fast);
 	} else {
 		page = page_pool_refill_alloc_cache(pool);
 	}
@@ -239,6 +290,7 @@ static struct page *__page_pool_alloc_page_order(struct page_pool *pool,
 		return NULL;
 	}
 
+	alloc_stat_inc(pool, slow_high_order);
 	page_pool_set_pp_info(pool, page);
 
 	/* Track how many pages are held 'in-flight' */
@@ -293,10 +345,12 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
 	}
 
 	/* Return last page */
-	if (likely(pool->alloc.count > 0))
+	if (likely(pool->alloc.count > 0)) {
 		page = pool->alloc.cache[--pool->alloc.count];
-	else
+		alloc_stat_inc(pool, slow);
+	} else {
 		page = NULL;
+	}
 
 	/* When page just alloc'ed is should/must have refcnt 1. */
 	return page;
@@ -394,7 +448,12 @@ static bool page_pool_recycle_in_ring(struct page_pool *pool, struct page *page)
 	else
 		ret = ptr_ring_produce_bh(&pool->ring, page);
 
-	return (ret == 0) ? true : false;
+	if (!ret) {
+		recycle_stat_inc(pool, ring);
+		return true;
+	}
+
+	return false;
 }
 
 /* Only allow direct recycling in special circumstances, into the
@@ -405,11 +464,14 @@ static bool page_pool_recycle_in_ring(struct page_pool *pool, struct page *page)
 static bool page_pool_recycle_in_cache(struct page *page,
 				       struct page_pool *pool)
 {
-	if (unlikely(pool->alloc.count == PP_ALLOC_CACHE_SIZE))
+	if (unlikely(pool->alloc.count == PP_ALLOC_CACHE_SIZE)) {
+		recycle_stat_inc(pool, cache_full);
 		return false;
+	}
 
 	/* Caller MUST have verified/know (page_ref_count(page) == 1) */
 	pool->alloc.cache[pool->alloc.count++] = page;
+	recycle_stat_inc(pool, cached);
 	return true;
 }
 
@@ -459,6 +521,7 @@ __page_pool_put_page(struct page_pool *pool, struct page *page,
 	 * doing refcnt based recycle tricks, meaning another process
 	 * will be invoking put_page.
 	 */
+	recycle_stat_inc(pool, released_refcnt);
 	/* Do not replace this with page_pool_return_page() */
 	page_pool_release_page(pool, page);
 	put_page(page);
@@ -472,6 +535,7 @@ void page_pool_put_defragged_page(struct page_pool *pool, struct page *page,
 	page = __page_pool_put_page(pool, page, dma_sync_size, allow_direct);
 	if (page && !page_pool_recycle_in_ring(pool, page)) {
 		/* Cache full, fallback to free pages */
+		recycle_stat_inc(pool, ring_full);
 		page_pool_return_page(pool, page);
 	}
 }
@@ -620,6 +684,9 @@ static void page_pool_free(struct page_pool *pool)
 	if (pool->p.flags & PP_FLAG_DMA_MAP)
 		put_device(pool->p.dev);
 
+#ifdef CONFIG_PAGE_POOL_STATS
+	free_percpu(pool->recycle_stats);
+#endif
 	kfree(pool);
 }