From: Ilias Apalodimas <ilias.apalodimas@linaro.org>
To: Yunsheng Lin <linyunsheng@huawei.com>
Cc: Matteo Croce <mcroce@linux.microsoft.com>,
netdev@vger.kernel.org, linux-mm@kvack.org,
Ayush Sawal <ayush.sawal@chelsio.com>,
Vinay Kumar Yadav <vinay.yadav@chelsio.com>,
Rohit Maheshwari <rohitm@chelsio.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
Marcin Wojtas <mw@semihalf.com>,
Russell King <linux@armlinux.org.uk>,
Mirko Lindner <mlindner@marvell.com>,
Stephen Hemminger <stephen@networkplumber.org>,
Tariq Toukan <tariqt@nvidia.com>,
Jesper Dangaard Brouer <hawk@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
John Fastabend <john.fastabend@gmail.com>,
Boris Pismenny <borisp@nvidia.com>, Arnd Bergmann <arnd@arndb.de>,
Andrew Morton <akpm@linux-foundation.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Vlastimil Babka <vbabka@suse.cz>, Yu Zhao <yuzhao@google.com>,
Will Deacon <will@kernel.org>, Fenghua Yu <fenghua.yu@intel.com>,
Roman Gushchin <guro@fb.com>, Hugh Dickins <hughd@google.com>,
Peter Xu <peterx@redhat.com>, Jason Gunthorpe <jgg@ziepe.ca>,
Jonathan Lemon <jonathan.lemon@gmail.com>,
Alexander Lobakin <alobakin@pm.me>,
Cong Wang <cong.wang@bytedance.com>, wenxu <wenxu@ucloud.cn>,
Kevin Hao <haokexin@gmail.com>,
Jakub Sitnicki <jakub@cloudflare.com>,
Marco Elver <elver@google.com>,
Willem de Bruijn <willemb@google.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Guillaume Nault <gnault@redhat.com>,
linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org,
bpf@vger.kernel.org, Matthew Wilcox <willy@infradead.org>,
Eric Dumazet <edumazet@google.com>,
David Ahern <dsahern@gmail.com>,
Lorenzo Bianconi <lorenzo@kernel.org>,
Saeed Mahameed <saeedm@nvidia.com>, Andrew Lunn <andrew@lunn.ch>,
Paolo Abeni <pabeni@redhat.com>,
Sven Auhagen <sven.auhagen@voleatech.de>
Subject: Re: [PATCH net-next v5 3/5] page_pool: Allow drivers to hint on SKB recycling
Date: Fri, 14 May 2021 12:17:50 +0300 [thread overview]
Message-ID: <YJ5APhzabmAKIKCE@apalos.home> (raw)
In-Reply-To: <212498cf-376b-2dac-e1cd-12c7cc7910c6@huawei.com>
On Fri, May 14, 2021 at 04:31:50PM +0800, Yunsheng Lin wrote:
> On 2021/5/14 15:36, Ilias Apalodimas wrote:
> > [...]
> >>> + return false;
> >>> +
> >>> + pp = (struct page_pool *)page->pp;
> >>> +
> >>> + /* 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;
> >>
> >> Why not only clear the page->pp when the page can not be recycled
> >> by the page pool? so that we do not need to set and clear it every
> >> time the page is recycled。
> >>
> >
> > If the page cannot be recycled, page->pp will not probably be set to begin
> > with. Since we don't embed the feature in page_pool and we require the
> > driver to explicitly enable it, as part of the 'skb flow', I'd rather keep
> > it as is. When we set/clear the page->pp, the page is probably already in
> > cache, so I doubt this will have any measurable impact.
>
> The point is that we already have the skb->pp_recycle to let driver to
> explicitly enable recycling, as part of the 'skb flow, if the page pool keep
> the page->pp while it owns the page, then the driver may only need to call
> one skb_mark_for_recycle() for a skb, instead of call skb_mark_for_recycle()
> for each page frag of a skb.
>
The driver is meant to call skb_mark_for_recycle for the skb and
page_pool_store_mem_info() for the fragments (in order to store page->pp).
Nothing bad will happen if you call skb_mark_for_recycle on a frag though,
but in any case you need to store the page_pool pointer of each frag to
struct page.
> Maybe we can add a parameter in "struct page_pool_params" to let driver
> to decide if the page pool ptr is stored in page->pp while the page pool
> owns the page?
Then you'd have to check the page pool config before saving the meta-data,
and you would have to make the skb path aware of that as well (I assume you
mean replace pp_recycle with this?).
If not and you just want to add an extra flag on page_pool_params and be able
to enable recycling depending on that flag, we just add a patch afterwards.
I am not sure we need an extra if for each packet though.
>
> Another thing accured to me is that if the driver use page from the
> page pool to form a skb, and it does not call skb_mark_for_recycle(),
> then there will be resource leaking, right? if yes, it seems the
> skb_mark_for_recycle() call does not seems to add any value?
>
Not really, the driver has 2 choices:
- call page_pool_release_page() once it receives the payload. That will
clean up dma mappings (if page pool is responsible for them) and free the
buffer
- call skb_mark_for_recycle(). Which will end up recycling the buffer.
If you call none of those, you'd leak a page, but that's a driver bug.
patches [4/5, 5/5] do that for two marvell drivers.
I really want to make drivers opt-in in the feature instead of always
enabling it.
Thanks
/Ilias
>
> >
> >>> + page_pool_put_full_page(pp, virt_to_head_page(data), false);
> >>> +
> >>> C(end);
> >
> > [...]
>
>
next prev parent reply other threads:[~2021-05-14 9:18 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-13 16:58 [PATCH net-next v5 0/5] page_pool: recycle buffers Matteo Croce
2021-05-13 16:58 ` [PATCH net-next v5 1/5] mm: add a signature in struct page Matteo Croce
2021-05-14 1:00 ` Matthew Wilcox
2021-05-14 1:34 ` Matteo Croce
2021-05-18 15:44 ` Matteo Croce
2021-05-13 16:58 ` [PATCH net-next v5 2/5] skbuff: add a parameter to __skb_frag_unref Matteo Croce
2021-05-13 16:58 ` [PATCH net-next v5 3/5] page_pool: Allow drivers to hint on SKB recycling Matteo Croce
2021-05-14 3:39 ` Yunsheng Lin
2021-05-14 7:36 ` Ilias Apalodimas
2021-05-14 8:31 ` Yunsheng Lin
2021-05-14 9:17 ` Ilias Apalodimas [this message]
2021-05-15 2:07 ` Yunsheng Lin
2021-05-17 6:38 ` Ilias Apalodimas
2021-05-17 8:25 ` Yunsheng Lin
2021-05-17 9:36 ` Ilias Apalodimas
2021-05-17 11:10 ` Yunsheng Lin
2021-05-17 11:35 ` Ilias Apalodimas
2021-05-13 16:58 ` [PATCH net-next v5 4/5] mvpp2: recycle buffers Matteo Croce
2021-05-13 18:20 ` Russell King (Oracle)
2021-05-13 23:52 ` Matteo Croce
2021-05-13 16:58 ` [PATCH net-next v5 5/5] mvneta: " Matteo Croce
2021-05-13 18:25 ` Russell King (Oracle)
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