[net-next v1 PATCH 2/4] page_pool: add destroy attempts counter and rename tracepoint

Jesper Dangaard Brouer
2019-11-15T15:06:18Z

When Jonathan change the page_pool to become responsible to its
own shutdown via deferred work queue, then the disconnect_cnt
counter was removed from xdp memory model tracepoint.

This patch change the page_pool_inflight tracepoint name to
page_pool_release, because it reflects the new responsability
better. And it reintroduces a counter that reflect the number of
times page_pool_release have been tried.

The counter is also used by the code, to only empty the alloc
cache once. With a stuck work queue running every second and
counter being 64-bit, it will overrun in approx 584 billion
years. For comparison, Earth lifetime expectancy is 7.5 billion
years, before the Sun will engulf, and destroy, the Earth.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
include/net/page_pool.h | 2 ++
include/trace/events/page_pool.h | 9 ++++++---
net/core/page_pool.c | 13 +++++++++++--
3 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/include/net/page_pool.h b/include/net/page_pool.h
index 1121faa99c12..ace881c15dcb 100644
--- a/include/net/page_pool.h
+++ b/include/net/page_pool.h
@@ -112,6 +112,8 @@ struct page_pool {
* refcnt serves purpose is to simplify drivers error handling.
*/
refcount_t user_cnt;
+
+ u64 destroy_cnt;
};

struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp);
diff --git a/include/trace/events/page_pool.h b/include/trace/events/page_pool.h
index 47b5ee880aa9..ee7f1aca7839 100644
--- a/include/trace/events/page_pool.h
+++ b/include/trace/events/page_pool.h
@@ -10,7 +10,7 @@

#include <net/page_pool.h>

-TRACE_EVENT(page_pool_inflight,
+TRACE_EVENT(page_pool_release,

TP_PROTO(const struct page_pool *pool,
s32 inflight, u32 hold, u32 release),
@@ -22,6 +22,7 @@ TRACE_EVENT(page_pool_inflight,
__field(s32, inflight)
__field(u32, hold)
__field(u32, release)
+ __field(u64, cnt)
),

TP_fast_assign(
@@ -29,10 +30,12 @@ TRACE_EVENT(page_pool_inflight,
__entry->inflight = inflight;
__entry->hold = hold;
__entry->release = release;
+ __entry->cnt = pool->destroy_cnt;
),

- TP_printk("page_pool=%p inflight=%d hold=%u release=%u",
- __entry->pool, __entry->inflight, __entry->hold, __entry->release)
+ TP_printk("page_pool=%p inflight=%d hold=%u release=%u cnt=%llu",
+ __entry->pool, __entry->inflight, __entry->hold,
+ __entry->release, __entry->cnt)
);

TRACE_EVENT(page_pool_state_release,
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index dfc2501c35d9..e28db2ef8e12 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -200,7 +200,7 @@ static s32 page_pool_inflight(struct page_pool *pool)

inflight = _distance(hold_cnt, release_cnt);

- trace_page_pool_inflight(pool, inflight, hold_cnt, release_cnt);
+ trace_page_pool_release(pool, inflight, hold_cnt, release_cnt);
WARN(inflight < 0, "Negative(%d) inflight packet-pages", inflight);

return inflight;
@@ -349,10 +349,13 @@ static void page_pool_free(struct page_pool *pool)
kfree(pool);
}

-static void page_pool_scrub(struct page_pool *pool)
+static void page_pool_empty_alloc_cache_once(struct page_pool *pool)
{
struct page *page;

+ if (pool->destroy_cnt)
+ return;
+
/* Empty alloc cache, assume caller made sure this is
* no-longer in use, and page_pool_alloc_pages() cannot be
* call concurrently.
@@ -361,6 +364,12 @@ static void page_pool_scrub(struct page_pool *pool)
page = pool->alloc.cache[--pool->alloc.count];
__page_pool_return_page(pool, page);
}
+}
+
+static void page_pool_scrub(struct page_pool *pool)
+{
+ page_pool_empty_alloc_cache_once(pool);
+ pool->destroy_cnt++;

/* No more consumers should exist, but producers could still
* be in-flight.