| Message ID | 20230803182038.2646541-7-aleksander.lobakin@intel.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | page_pool: a couple of assorted optimizations | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Clearly marked for net-next, async |
| netdev/apply | fail | Patch does not apply to net-next |
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 85f82a6a08dc..33fdf04d4334 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -902,8 +902,10 @@ bool napi_pp_put_page(struct page *page, bool napi_safe) /* Allow direct recycle if we have reasons to believe that we are * in the same context as the consumer would run, so there's * no possible race. + * __page_pool_put_page() makes sure we're not in hardirq context + * and interrupts are enabled prior to accessing the cache. */ - if (napi_safe) { + if (napi_safe || in_softirq()) { const struct napi_struct *napi = READ_ONCE(pp->p.napi); allow_direct = napi &&
Commit 8c48eea3adf3 ("page_pool: allow caching from safely localized NAPI") allowed direct recycling of skb pages to their PP for some cases, but unfortunately missed a couple of other majors. For example, %XDP_DROP in skb mode. The netstack just calls kfree_skb(), which unconditionally passes `false` as @napi_safe. Thus, all pages go through ptr_ring and locks, although most of time we're actually inside the NAPI polling this PP is linked with, so that it would be perfectly safe to recycle pages directly. Let's address such. If @napi_safe is true, we're fine, don't change anything for this path. But if it's false, check whether we are in the softirq context. It will most likely be so and then if ->list_owner is our current CPU, we're good to use direct recycling, even though @napi_safe is false -- concurrent access is excluded. in_softirq() protection is needed mostly due to we can hit this place in the process context (not the hardirq though). For the mentioned xdp-drop-skb-mode case, the improvement I got is 3-4% in Mpps. As for page_pool stats, recycle_ring is now 0 and alloc_slow counter doesn't change most of time, which means the MM layer is not even called to allocate any new pages. Suggested-by: Jakub Kicinski <kuba@kernel.org> # in_softirq() Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com> --- net/core/skbuff.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)