Netdev Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Ilias Apalodimas <ilias.apalodimas@linaro.org>
To: Yunsheng Lin <linyunsheng@huawei.com>
Cc: Jesper Dangaard Brouer <jbrouer@redhat.com>,
	davem@davemloft.net, kuba@kernel.org, linuxarm@openeuler.org,
	yisen.zhuang@huawei.com, salil.mehta@huawei.com,
	thomas.petazzoni@bootlin.com, mw@semihalf.com,
	linux@armlinux.org.uk, hawk@kernel.org, ast@kernel.org,
	daniel@iogearbox.net, john.fastabend@gmail.com,
	akpm@linux-foundation.org, peterz@infradead.org, will@kernel.org,
	willy@infradead.org, vbabka@suse.cz, fenghua.yu@intel.com,
	guro@fb.com, peterx@redhat.com, feng.tang@intel.com,
	jgg@ziepe.ca, mcroce@microsoft.com, hughd@google.com,
	jonathan.lemon@gmail.com, alobakin@pm.me, willemb@google.com,
	wenxu@ucloud.cn, cong.wang@bytedance.com, haokexin@gmail.com,
	nogikh@google.com, elver@google.com, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
	Alexander Duyck <alexander.duyck@gmail.com>
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)
In-Reply-To: <33aee58e-b1d5-ce7b-1576-556d0da28560@huawei.com>

> >>

[...]

> >>>
> >>>
> >>>> 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
> patch.
> 
> 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
for it.
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
> thinking.
> 

Fair enough. It's complex in both scenarios so if people think it's useful
I am not against adding it in the API.


Thanks
/Ilias
> > 
> > 
> > Cheers
> > /Ilias
> >>
> >>>
> >>>  __page_frag_cache_refill() + __page_frag_cache_drain() + page_frag_alloc_align()
> >>>
> >>>
> >>
> >> [...]
> > .
> > 

  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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=YOQRxS+MUFIRubsf@enceladus \
    --to=ilias.apalodimas@linaro.org \
    --cc=akpm@linux-foundation.org \
    --cc=alexander.duyck@gmail.com \
    --cc=alobakin@pm.me \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=cong.wang@bytedance.com \
    --cc=daniel@iogearbox.net \
    --cc=davem@davemloft.net \
    --cc=elver@google.com \
    --cc=feng.tang@intel.com \
    --cc=fenghua.yu@intel.com \
    --cc=guro@fb.com \
    --cc=haokexin@gmail.com \
    --cc=hawk@kernel.org \
    --cc=hughd@google.com \
    --cc=jbrouer@redhat.com \
    --cc=jgg@ziepe.ca \
    --cc=john.fastabend@gmail.com \
    --cc=jonathan.lemon@gmail.com \
    --cc=kuba@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@armlinux.org.uk \
    --cc=linuxarm@openeuler.org \
    --cc=linyunsheng@huawei.com \
    --cc=mcroce@microsoft.com \
    --cc=mw@semihalf.com \
    --cc=netdev@vger.kernel.org \
    --cc=nogikh@google.com \
    --cc=peterx@redhat.com \
    --cc=peterz@infradead.org \
    --cc=salil.mehta@huawei.com \
    --cc=thomas.petazzoni@bootlin.com \
    --cc=vbabka@suse.cz \
    --cc=wenxu@ucloud.cn \
    --cc=will@kernel.org \
    --cc=willemb@google.com \
    --cc=willy@infradead.org \
    --cc=yisen.zhuang@huawei.com \
    --subject='Re: [PATCH net-next RFC 1/2] page_pool: add page recycling support based on elevated refcnt' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).