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From: Ilias Apalodimas <firstname.lastname@example.org>
To: Yunsheng Lin <email@example.com>
Cc: Jesper Dangaard Brouer <firstname.lastname@example.org>,
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Alexander Duyck <firstname.lastname@example.org>
Subject: Re: [PATCH net-next RFC 1/2] page_pool: add page recycling support based on elevated refcnt
Date: Tue, 6 Jul 2021 11:18:13 +0300 [thread overview]
Message-ID: <YOQRxS+MUFIRubsf@enceladus> (raw)
> >>>> So add elevated refcnt support in page pool, and support
> >>>> allocating page frag to enable multi-frames-per-page based
> >>>> on the elevated refcnt support.
> >>>> As the elevated refcnt is per page, and there is no space
> >>>> for that in "struct page" now, so add a dynamically allocated
> >>>> "struct page_pool_info" to record page pool ptr and refcnt
> >>>> corrsponding to a page for now. Later, we can recycle the
> >>>> "struct page_pool_info" too, or use part of page memory to
> >>>> record pp_info.
> >>> I'm not happy with allocating a memory (slab) object "struct page_pool_info" per page.
> >>> This also gives us an extra level of indirection.
> >> I'm not happy with that either, if there is better way to
> >> avoid that, I will be happy to change it:)
> > I think what we have to answer here is, do we want and does it make sense
> > for page_pool to do the housekeeping of the buffer splitting or are we
> > better of having each driver do that. IIRC your previous patch on top of
> > the original recycling patchset was just 'atomic' refcnts on top of page pool.
> You are right that driver was doing the the buffer splitting in previous
> The reason why I abandoned that is:
> 1. Currently the meta-data of page in the driver is per desc, which means
> it might not be able to use first half of a page for a desc, and the
> second half of the same page for another desc, this ping-pong way of
> reusing the whole page for only one desc in the driver seems unnecessary
> and waste a lot of memory when there is already reusing in the page pool.
> 2. Easy use of API for the driver too, which means the driver uses
> page_pool_dev_alloc_frag() and page_pool_put_full_page() for elevated
> refcnt case, corresponding to page_pool_dev_alloc_pages() and
> page_pool_put_full_page() for non-elevated refcnt case, the driver does
> not need to worry about the meta-data of a page.
Ok that makes sense. We'll need the complexity anyway and I said I don't
have any strong opinions yet, we might as well make page_pool responsible
What we need to keep in mind is that page_pool was primarily used for XDP
packets. We need to make sure we have no performance regressions there.
However I don't have access to > 10gbit NICs with XDP support. Can anyone
apply the patchset and check the performance?
> >> Aside from the performance improvement, there is memory usage
> >> decrease for 64K page size kernel, which means a 64K page can
> >> be used by 32 description with 2k buffer size, and that is a
> >> lot of memory saving for 64 page size kernel comparing to the
> >> current split page reusing implemented in the driver.
> > Whether the driver or page_pool itself keeps the meta-data, the outcome
> > here won't change. We'll still be able to use page frags.
> As above, it is the ping-pong way of reusing when the driver keeps the
> meta-data, and it is page-frag way of reusing when the page pool keeps
> the meta-data.
> I am not sure if the page-frag way of reusing is possible when we still
> keep the meta-data in the driver, which seems very complex at the initial
Fair enough. It's complex in both scenarios so if people think it's useful
I am not against adding it in the API.
> > Cheers
> > /Ilias
> >>> __page_frag_cache_refill() + __page_frag_cache_drain() + page_frag_alloc_align()
> >> [...]
> > .
next prev parent reply other threads:[~2021-07-06 8:18 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-30 9:17 [PATCH net-next RFC 0/2] add elevated refcnt support for page pool Yunsheng Lin
2021-06-30 9:17 ` [PATCH net-next RFC 1/2] page_pool: add page recycling support based on elevated refcnt Yunsheng Lin
2021-07-02 9:42 ` Jesper Dangaard Brouer
2021-07-02 10:15 ` Yunsheng Lin
2021-07-06 4:54 ` Ilias Apalodimas
2021-07-06 6:46 ` Yunsheng Lin
2021-07-06 8:18 ` Ilias Apalodimas [this message]
2021-07-06 20:45 ` Alexander Duyck
2021-07-07 3:05 ` Yunsheng Lin
2021-07-07 15:01 ` Alexander Duyck
2021-07-07 19:03 ` Ilias Apalodimas
2021-07-07 21:49 ` Alexander Duyck
2021-07-08 14:21 ` Ilias Apalodimas
2021-07-08 14:24 ` Alexander Duyck
2021-07-08 14:50 ` Ilias Apalodimas
2021-07-08 15:17 ` Ilias Apalodimas
2021-07-08 15:29 ` Alexander Duyck
2021-07-08 15:36 ` Ilias Apalodimas
2021-07-08 15:41 ` Alexander Duyck
2021-07-08 15:47 ` Ilias Apalodimas
2021-07-08 2:27 ` Yunsheng Lin
2021-07-08 15:36 ` Alexander Duyck
2021-07-09 6:26 ` Yunsheng Lin
2021-07-09 14:15 ` Alexander Duyck
2021-07-10 9:16 ` [Linuxarm] " Yunsheng Lin
2021-06-30 9:17 ` [PATCH net-next RFC 2/2] net: hns3: support skb's frag page recycling based on page pool Yunsheng Lin
2021-07-02 8:36 ` [PATCH net-next RFC 0/2] add elevated refcnt support for " Ilias Apalodimas
2021-07-02 13:39 ` Matteo Croce
2021-07-06 15:51 ` Russell King (Oracle)
2021-07-06 23:19 ` Matteo Croce
2021-07-07 16:50 ` Marcin Wojtas
2021-07-09 4:15 ` Matteo Croce
2021-07-09 6:40 ` Yunsheng Lin
2021-07-09 6:42 ` Ilias Apalodimas
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