kernel/include/net/page_pool.h, branch linux-rolling-stable

page_pool: split types and declarations from page_pool.h

2023-08-07T20:05:19Z

Split types and pure function declarations from page_pool.h and add them in page_page/types.h, so that C sources can include page_pool.h and headers should generally only include page_pool/types.h as suggested by jakub. Rename page_pool.h to page_pool/helpers.h to have both in one place. Signed-off-by: Yunsheng Lin Suggested-by: Jakub Kicinski Signed-off-by: Alexander Lobakin Reviewed-by: Alexander Duyck Link: https://lore.kernel.org/r/20230804180529.2483231-2-aleksander.lobakin@intel.com [Jakub: change microsoft/mana, fix kdoc paths in Documentation] Signed-off-by: Jakub Kicinski

docs: net: page_pool: use kdoc to avoid duplicating the information

2023-08-03T16:54:24Z

All struct members of the driver-facing APIs are documented twice, in the code and under Documentation. This is a bit tedious. I also get the feeling that a lot of developers will read the header when coding, rather than the doc. Bring the two a little closer together by using kdoc for structs and functions. Using kdoc also gives us links (mentioning a function or struct in the text gets replaced by a link to its doc). Reviewed-by: Randy Dunlap Tested-by: Randy Dunlap Acked-by: Jesper Dangaard Brouer Link: https://lore.kernel.org/r/20230802161821.3621985-3-kuba@kernel.org Signed-off-by: Jakub Kicinski

net: page_pool: hide page_pool_release_page()

2023-07-22T01:50:18Z

There seems to be no user calling page_pool_release_page() for legit reasons, all the users simply haven't been converted to skb-based recycling, yet. Previous changes converted them. Update the docs, and unexport the function. Link: https://lore.kernel.org/r/20230720010409.1967072-4-kuba@kernel.org Reviewed-by: Alexander Lobakin Signed-off-by: Jakub Kicinski

page_pool: fix inconsistency for page_pool_ring_[un]lock()

2023-05-24T03:25:13Z

page_pool_ring_[un]lock() use in_softirq() to decide which spin lock variant to use, and when they are called in the context with in_softirq() being false, spin_lock_bh() is called in page_pool_ring_lock() while spin_unlock() is called in page_pool_ring_unlock(), because spin_lock_bh() has disabled the softirq in page_pool_ring_lock(), which causes inconsistency for spin lock pair calling. This patch fixes it by returning in_softirq state from page_pool_producer_lock(), and use it to decide which spin lock variant to use in page_pool_producer_unlock(). As pool->ring has both producer and consumer lock, so rename it to page_pool_producer_[un]lock() to reflect the actual usage. Also move them to page_pool.c as they are only used there, and remove the 'inline' as the compiler may have better idea to do inlining or not. Fixes: 7886244736a4 ("net: page_pool: Add bulk support for ptr_ring") Signed-off-by: Yunsheng Lin Acked-by: Jesper Dangaard Brouer Acked-by: Ilias Apalodimas Link: https://lore.kernel.org/r/20230522031714.5089-1-linyunsheng@huawei.com Signed-off-by: Jakub Kicinski

page_pool: unlink from napi during destroy

2023-04-21T02:13:37Z

Jesper points out that we must prevent recycling into cache after page_pool_destroy() is called, because page_pool_destroy() is not synchronized with recycling (some pages may still be outstanding when destroy() gets called). I assumed this will not happen because NAPI can't be scheduled if its page pool is being destroyed. But I missed the fact that NAPI may get reused. For instance when user changes ring configuration driver may allocate a new page pool, stop NAPI, swap, start NAPI, and then destroy the old pool. The NAPI is running so old page pool will think it can recycle to the cache, but the consumer at that point is the destroy() path, not NAPI. To avoid extra synchronization let the drivers do "unlinking" during the "swap" stage while NAPI is indeed disabled. Fixes: 8c48eea3adf3 ("page_pool: allow caching from safely localized NAPI") Reported-by: Jesper Dangaard Brouer Link: https://lore.kernel.org/all/e8df2654-6a5b-3c92-489d-2fe5e444135f@redhat.com/ Acked-by: Jesper Dangaard Brouer Link: https://lore.kernel.org/r/20230419182006.719923-1-kuba@kernel.org Signed-off-by: Jakub Kicinski

page_pool: allow caching from safely localized NAPI

2023-04-15T01:56:12Z

Recent patches to mlx5 mentioned a regression when moving from driver local page pool to only using the generic page pool code. Page pool has two recycling paths (1) direct one, which runs in safe NAPI context (basically consumer context, so producing can be lockless); and (2) via a ptr_ring, which takes a spin lock because the freeing can happen from any CPU; producer and consumer may run concurrently. Since the page pool code was added, Eric introduced a revised version of deferred skb freeing. TCP skbs are now usually returned to the CPU which allocated them, and freed in softirq context. This places the freeing (producing of pages back to the pool) enticingly close to the allocation (consumer). If we can prove that we're freeing in the same softirq context in which the consumer NAPI will run - lockless use of the cache is perfectly fine, no need for the lock. Let drivers link the page pool to a NAPI instance. If the NAPI instance is scheduled on the same CPU on which we're freeing - place the pages in the direct cache. With that and patched bnxt (XDP enabled to engage the page pool, sigh, bnxt really needs page pool work :() I see a 2.6% perf boost with a TCP stream test (app on a different physical core than softirq). The CPU use of relevant functions decreases as expected: page_pool_refill_alloc_cache 1.17% -> 0% _raw_spin_lock 2.41% -> 0.98% Only consider lockless path to be safe when NAPI is scheduled - in practice this should cover majority if not all of steady state workloads. It's usually the NAPI kicking in that causes the skb flush. The main case we'll miss out on is when application runs on the same CPU as NAPI. In that case we don't use the deferred skb free path. Reviewed-by: Tariq Toukan Acked-by: Jesper Dangaard Brouer Tested-by: Dragos Tatulea Signed-off-by: Jakub Kicinski

page_pool: add a comment explaining the fragment counter usage

2023-02-21T17:15:39Z

When reading the page_pool code the first impression is that keeping two separate counters, one being the page refcnt and the other being fragment pp_frag_count, is counter-intuitive. However without that fragment counter we don't know when to reliably destroy or sync the outstanding DMA mappings. So let's add a comment explaining this part. Reviewed-by: Alexander Duyck Signed-off-by: Ilias Apalodimas Acked-by: Jesper Dangaard Brouer Link: https://lore.kernel.org/r/20230217222130.85205-1-ilias.apalodimas@linaro.org Signed-off-by: Jakub Kicinski

net: page_pool: use in_softirq() instead

2023-02-06T09:15:22Z

We use BH context only for synchronization, so we don't care if it's actually serving softirq or not. As a side node, in case of threaded NAPI, in_serving_softirq() will return false because it's in process context with BH off, making page_pool_recycle_in_cache() unreachable. Signed-off-by: Qingfang DENG Tested-by: Felix Fietkau Signed-off-by: David S. Miller

net: page_pool: introduce ethtool stats

2022-04-15T09:43:47Z

Introduce page_pool APIs to report stats through ethtool and reduce duplicated code in each driver. Signed-off-by: Lorenzo Bianconi Reviewed-by: Jakub Kicinski Reviewed-by: Ilias Apalodimas Signed-off-by: David S. Miller

page_pool: Add function to batch and return stats

2022-03-03T09:55:28Z

Adds a function page_pool_get_stats which can be used by drivers to obtain stats for a specified page_pool. Signed-off-by: Joe Damato Acked-by: Jesper Dangaard Brouer Reviewed-by: Ilias Apalodimas Signed-off-by: David S. Miller