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Message-ID: <YLqCAEVG+aLNGlIi@casper.infradead.org>
Date: Fri, 4 Jun 2021 20:41:52 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Matteo Croce <mcroce@...ux.microsoft.com>
Cc: netdev@...r.kernel.org, linux-mm@...ck.org,
Ayush Sawal <ayush.sawal@...lsio.com>,
Vinay Kumar Yadav <vinay.yadav@...lsio.com>,
Rohit Maheshwari <rohitm@...lsio.com>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
Marcin Wojtas <mw@...ihalf.com>,
Russell King <linux@...linux.org.uk>,
Mirko Lindner <mlindner@...vell.com>,
Stephen Hemminger <stephen@...workplumber.org>,
Tariq Toukan <tariqt@...dia.com>,
Jesper Dangaard Brouer <hawk@...nel.org>,
Ilias Apalodimas <ilias.apalodimas@...aro.org>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
John Fastabend <john.fastabend@...il.com>,
Boris Pismenny <borisp@...dia.com>,
Arnd Bergmann <arnd@...db.de>,
Andrew Morton <akpm@...ux-foundation.org>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Vlastimil Babka <vbabka@...e.cz>, Yu Zhao <yuzhao@...gle.com>,
Will Deacon <will@...nel.org>,
Fenghua Yu <fenghua.yu@...el.com>,
Roman Gushchin <guro@...com>, Hugh Dickins <hughd@...gle.com>,
Peter Xu <peterx@...hat.com>, Jason Gunthorpe <jgg@...pe.ca>,
Jonathan Lemon <jonathan.lemon@...il.com>,
Alexander Lobakin <alobakin@...me>,
Cong Wang <cong.wang@...edance.com>, wenxu <wenxu@...oud.cn>,
Kevin Hao <haokexin@...il.com>,
Jakub Sitnicki <jakub@...udflare.com>,
Marco Elver <elver@...gle.com>,
Willem de Bruijn <willemb@...gle.com>,
Miaohe Lin <linmiaohe@...wei.com>,
Yunsheng Lin <linyunsheng@...wei.com>,
Guillaume Nault <gnault@...hat.com>,
linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
bpf@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
David Ahern <dsahern@...il.com>,
Lorenzo Bianconi <lorenzo@...nel.org>,
Saeed Mahameed <saeedm@...dia.com>,
Andrew Lunn <andrew@...n.ch>, Paolo Abeni <pabeni@...hat.com>,
Sven Auhagen <sven.auhagen@...eatech.de>
Subject: Re: [PATCH net-next v7 3/5] page_pool: Allow drivers to hint on SKB
recycling
On Fri, Jun 04, 2021 at 08:33:47PM +0200, Matteo Croce wrote:
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 7fcfea7e7b21..057b40ad29bd 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -40,6 +40,9 @@
> #if IS_ENABLED(CONFIG_NF_CONNTRACK)
> #include <linux/netfilter/nf_conntrack_common.h>
> #endif
> +#ifdef CONFIG_PAGE_POOL
> +#include <net/page_pool.h>
> +#endif
I'm not a huge fan of conditional includes ... any reason to not include
it always?
> @@ -3088,7 +3095,13 @@ static inline void skb_frag_ref(struct sk_buff *skb, int f)
> */
> static inline void __skb_frag_unref(skb_frag_t *frag, bool recycle)
> {
> - put_page(skb_frag_page(frag));
> + struct page *page = skb_frag_page(frag);
> +
> +#ifdef CONFIG_PAGE_POOL
> + if (recycle && page_pool_return_skb_page(page_address(page)))
> + return;
It feels weird to have a page here, convert it back to an address,
then convert it back to a head page in page_pool_return_skb_page().
How about passing 'page' here, calling compound_head() in
page_pool_return_skb_page() and calling virt_to_page() in skb_free_head()?
> @@ -251,4 +253,11 @@ static inline void page_pool_ring_unlock(struct page_pool *pool)
> spin_unlock_bh(&pool->ring.producer_lock);
> }
>
> +/* Store mem_info on struct page and use it while recycling skb frags */
> +static inline
> +void page_pool_store_mem_info(struct page *page, struct page_pool *pp)
> +{
> + page->pp = pp;
I'm not sure this wrapper needs to exist.
> +}
> +
> #endif /* _NET_PAGE_POOL_H */
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index e1321bc9d316..a03f48f45696 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -628,3 +628,26 @@ void page_pool_update_nid(struct page_pool *pool, int new_nid)
> }
> }
> EXPORT_SYMBOL(page_pool_update_nid);
> +
> +bool page_pool_return_skb_page(void *data)
> +{
> + struct page_pool *pp;
> + struct page *page;
> +
> + page = virt_to_head_page(data);
> + if (unlikely(page->pp_magic != PP_SIGNATURE))
> + return false;
> +
> + pp = (struct page_pool *)page->pp;
You don't need the cast any more.
> + /* Driver set this to memory recycling info. Reset it on recycle.
> + * This will *not* work for NIC using a split-page memory model.
> + * The page will be returned to the pool here regardless of the
> + * 'flipped' fragment being in use or not.
> + */
> + page->pp = NULL;
> + page_pool_put_full_page(pp, page, false);
> +
> + return true;
> +}
> +EXPORT_SYMBOL(page_pool_return_skb_page);
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 12b7e90dd2b5..f769f08e7b32 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -70,6 +70,9 @@
> #include <net/xfrm.h>
> #include <net/mpls.h>
> #include <net/mptcp.h>
> +#ifdef CONFIG_PAGE_POOL
> +#include <net/page_pool.h>
> +#endif
>
> #include <linux/uaccess.h>
> #include <trace/events/skb.h>
> @@ -645,10 +648,15 @@ static void skb_free_head(struct sk_buff *skb)
> {
> unsigned char *head = skb->head;
>
> - if (skb->head_frag)
> + if (skb->head_frag) {
> +#ifdef CONFIG_PAGE_POOL
> + if (skb->pp_recycle && page_pool_return_skb_page(head))
> + return;
> +#endif
put this in a header file:
static inline bool skb_pp_recycle(struct sk_buff *skb, void *data)
{
if (!IS_ENABLED(CONFIG_PAGE_POOL) || !skb->pp_recycle)
return false;
return page_pool_return_skb_page(virt_to_page(data));
}
then this becomes:
if (skb->head_frag) {
if (skb_pp_recycle(skb, head))
return;
> skb_free_frag(head);
> - else
> + } else {
> kfree(head);
> + }
> }
>
> static void skb_release_data(struct sk_buff *skb)
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