* [PATCH net-next] page_pool: fix logic in __page_pool_get_cached
@ 2019-08-13 17:45 Jonathan Lemon
2019-08-14 12:29 ` Jesper Dangaard Brouer
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Jonathan Lemon @ 2019-08-13 17:45 UTC (permalink / raw)
To: netdev, davem
Cc: brouer, ilias.apalodimas, saeedm, ttoukan.linux, kernel-team
__page_pool_get_cached() will return NULL when the ring is
empty, even if there are pages present in the lookaside cache.
It is also possible to refill the cache, and then return a
NULL page.
Restructure the logic so eliminate both cases.
Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
---
net/core/page_pool.c | 39 ++++++++++++++++-----------------------
1 file changed, 16 insertions(+), 23 deletions(-)
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 68510eb869ea..de09a74a39a4 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -82,12 +82,9 @@ EXPORT_SYMBOL(page_pool_create);
static struct page *__page_pool_get_cached(struct page_pool *pool)
{
struct ptr_ring *r = &pool->ring;
+ bool refill = false;
struct page *page;
- /* Quicker fallback, avoid locks when ring is empty */
- if (__ptr_ring_empty(r))
- return NULL;
-
/* Test for safe-context, caller should provide this guarantee */
if (likely(in_serving_softirq())) {
if (likely(pool->alloc.count)) {
@@ -95,27 +92,23 @@ static struct page *__page_pool_get_cached(struct page_pool *pool)
page = pool->alloc.cache[--pool->alloc.count];
return page;
}
- /* Slower-path: Alloc array empty, time to refill
- *
- * Open-coded bulk ptr_ring consumer.
- *
- * Discussion: the ring consumer lock is not really
- * needed due to the softirq/NAPI protection, but
- * later need the ability to reclaim pages on the
- * ring. Thus, keeping the locks.
- */
- spin_lock(&r->consumer_lock);
- while ((page = __ptr_ring_consume(r))) {
- if (pool->alloc.count == PP_ALLOC_CACHE_REFILL)
- break;
- pool->alloc.cache[pool->alloc.count++] = page;
- }
- spin_unlock(&r->consumer_lock);
- return page;
+ refill = true;
}
- /* Slow-path: Get page from locked ring queue */
- page = ptr_ring_consume(&pool->ring);
+ /* Quicker fallback, avoid locks when ring is empty */
+ if (__ptr_ring_empty(r))
+ return NULL;
+
+ /* Slow-path: Get page from locked ring queue,
+ * refill alloc array if requested.
+ */
+ spin_lock(&r->consumer_lock);
+ page = __ptr_ring_consume(r);
+ if (refill)
+ pool->alloc.count = __ptr_ring_consume_batched(r,
+ pool->alloc.cache,
+ PP_ALLOC_CACHE_REFILL);
+ spin_unlock(&r->consumer_lock);
return page;
}
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH net-next] page_pool: fix logic in __page_pool_get_cached
2019-08-13 17:45 [PATCH net-next] page_pool: fix logic in __page_pool_get_cached Jonathan Lemon
@ 2019-08-14 12:29 ` Jesper Dangaard Brouer
2019-08-14 12:49 ` Ilias Apalodimas
2019-08-15 19:28 ` David Miller
2 siblings, 0 replies; 4+ messages in thread
From: Jesper Dangaard Brouer @ 2019-08-14 12:29 UTC (permalink / raw)
To: Jonathan Lemon
Cc: netdev, davem, ilias.apalodimas, saeedm, ttoukan.linux,
kernel-team, brouer
On Tue, 13 Aug 2019 10:45:09 -0700
Jonathan Lemon <jonathan.lemon@gmail.com> wrote:
> __page_pool_get_cached() will return NULL when the ring is
> empty, even if there are pages present in the lookaside cache.
>
> It is also possible to refill the cache, and then return a
> NULL page.
>
> Restructure the logic so eliminate both cases.
>
> Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Thanks for catching and improving this!
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net-next] page_pool: fix logic in __page_pool_get_cached
2019-08-13 17:45 [PATCH net-next] page_pool: fix logic in __page_pool_get_cached Jonathan Lemon
2019-08-14 12:29 ` Jesper Dangaard Brouer
@ 2019-08-14 12:49 ` Ilias Apalodimas
2019-08-15 19:28 ` David Miller
2 siblings, 0 replies; 4+ messages in thread
From: Ilias Apalodimas @ 2019-08-14 12:49 UTC (permalink / raw)
To: Jonathan Lemon; +Cc: netdev, davem, brouer, saeedm, ttoukan.linux, kernel-team
Hi Jonathan,
Thanks!
On Tue, Aug 13, 2019 at 10:45:09AM -0700, Jonathan Lemon wrote:
> __page_pool_get_cached() will return NULL when the ring is
> empty, even if there are pages present in the lookaside cache.
>
> It is also possible to refill the cache, and then return a
> NULL page.
>
> Restructure the logic so eliminate both cases.
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
>
> Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
> ---
> net/core/page_pool.c | 39 ++++++++++++++++-----------------------
> 1 file changed, 16 insertions(+), 23 deletions(-)
>
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index 68510eb869ea..de09a74a39a4 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -82,12 +82,9 @@ EXPORT_SYMBOL(page_pool_create);
> static struct page *__page_pool_get_cached(struct page_pool *pool)
> {
> struct ptr_ring *r = &pool->ring;
> + bool refill = false;
> struct page *page;
>
> - /* Quicker fallback, avoid locks when ring is empty */
> - if (__ptr_ring_empty(r))
> - return NULL;
> -
> /* Test for safe-context, caller should provide this guarantee */
> if (likely(in_serving_softirq())) {
> if (likely(pool->alloc.count)) {
> @@ -95,27 +92,23 @@ static struct page *__page_pool_get_cached(struct page_pool *pool)
> page = pool->alloc.cache[--pool->alloc.count];
> return page;
> }
> - /* Slower-path: Alloc array empty, time to refill
> - *
> - * Open-coded bulk ptr_ring consumer.
> - *
> - * Discussion: the ring consumer lock is not really
> - * needed due to the softirq/NAPI protection, but
> - * later need the ability to reclaim pages on the
> - * ring. Thus, keeping the locks.
> - */
> - spin_lock(&r->consumer_lock);
> - while ((page = __ptr_ring_consume(r))) {
> - if (pool->alloc.count == PP_ALLOC_CACHE_REFILL)
> - break;
> - pool->alloc.cache[pool->alloc.count++] = page;
> - }
> - spin_unlock(&r->consumer_lock);
> - return page;
> + refill = true;
> }
>
> - /* Slow-path: Get page from locked ring queue */
> - page = ptr_ring_consume(&pool->ring);
> + /* Quicker fallback, avoid locks when ring is empty */
> + if (__ptr_ring_empty(r))
> + return NULL;
> +
> + /* Slow-path: Get page from locked ring queue,
> + * refill alloc array if requested.
> + */
> + spin_lock(&r->consumer_lock);
> + page = __ptr_ring_consume(r);
> + if (refill)
> + pool->alloc.count = __ptr_ring_consume_batched(r,
> + pool->alloc.cache,
> + PP_ALLOC_CACHE_REFILL);
> + spin_unlock(&r->consumer_lock);
> return page;
> }
>
> --
> 2.17.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net-next] page_pool: fix logic in __page_pool_get_cached
2019-08-13 17:45 [PATCH net-next] page_pool: fix logic in __page_pool_get_cached Jonathan Lemon
2019-08-14 12:29 ` Jesper Dangaard Brouer
2019-08-14 12:49 ` Ilias Apalodimas
@ 2019-08-15 19:28 ` David Miller
2 siblings, 0 replies; 4+ messages in thread
From: David Miller @ 2019-08-15 19:28 UTC (permalink / raw)
To: jonathan.lemon
Cc: netdev, brouer, ilias.apalodimas, saeedm, ttoukan.linux, kernel-team
From: Jonathan Lemon <jonathan.lemon@gmail.com>
Date: Tue, 13 Aug 2019 10:45:09 -0700
> __page_pool_get_cached() will return NULL when the ring is
> empty, even if there are pages present in the lookaside cache.
>
> It is also possible to refill the cache, and then return a
> NULL page.
>
> Restructure the logic so eliminate both cases.
>
> Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Applied.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2019-08-13 17:45 [PATCH net-next] page_pool: fix logic in __page_pool_get_cached Jonathan Lemon
2019-08-14 12:29 ` Jesper Dangaard Brouer
2019-08-14 12:49 ` Ilias Apalodimas
2019-08-15 19:28 ` David Miller
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