From: Paolo Abeni <pabeni@redhat.com>
To: Alexander H Duyck <alexander.duyck@gmail.com>,
Eric Dumazet <eric.dumazet@gmail.com>,
"David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>
Cc: netdev <netdev@vger.kernel.org>,
Eric Dumazet <edumazet@google.com>,
Alexander Duyck <alexanderduyck@fb.com>,
"Michael S . Tsirkin" <mst@redhat.com>,
Greg Thelen <gthelen@google.com>
Subject: Re: [PATCH net] net: avoid 32 x truesize under-estimation for tiny skbs
Date: Thu, 08 Sep 2022 20:01:42 +0200 [thread overview]
Message-ID: <f3f867cf6814510817b253e6aca997cdd3acc48a.camel@redhat.com> (raw)
In-Reply-To: <cf264865cb1613c0e7acf4bbc1ed345533767822.camel@gmail.com>
On Thu, 2022-09-08 at 07:53 -0700, Alexander H Duyck wrote:
> On Thu, 2022-09-08 at 13:00 +0200, Paolo Abeni wrote:
> > In most build GRO_MAX_HEAD packets are even larger (should be 640)
>
> Right, which is why I am thinking we may want to default to a 1K slice.
Ok it looks like there is agreement to force a minimum frag size of 1K.
Side note: that should not cause a memory usage increase compared to
the slab allocator as kmalloc(640) should use the kmalloc-1k slab.
[...]
> > >
> > If the pagecnt optimization should be dropped, it would be probably
> > more straight-forward to use/adapt 'page_frag' for the page_order0
> > allocator.
>
> That would make sense. Basically we could get rid of the pagecnt bias
> and add the fixed number of slices to the count at allocation so we
> would just need to track the offset to decide when we need to allocate
> a new page. In addtion if we are flushing the page when it is depleted
> we don't have to mess with the pfmemalloc logic.
Uhmm... it looks like that the existing page_frag allocator does not
always flush the depleted page:
bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t gfp)
{
if (pfrag->page) {
if (page_ref_count(pfrag->page) == 1) {
pfrag->offset = 0;
return true;
}
so I'll try adding some separate/specialized code and see if the
overall complexity would be reasonable.
> > BTW it's quite strange/confusing having to very similar APIs (page_frag
> > and page_frag_cache) with very similar names and no references between
> > them.
>
> I'm not sure what you are getting at here. There are plenty of
> references between them, they just aren't direct.
Looking/greping the tree I could not trivially understand when 'struct
page_frag' should be preferred over 'struct page_frag_cache' and/or
vice versa, I had to look at the respective implementation details.
Thanks,
Paolo
next prev parent reply other threads:[~2022-09-08 18:02 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-13 16:18 [PATCH net] net: avoid 32 x truesize under-estimation for tiny skbs Eric Dumazet
2021-01-13 18:00 ` Alexander Duyck
2021-01-13 19:19 ` Michael S. Tsirkin
2021-01-13 22:23 ` David Laight
2021-01-14 5:16 ` Eric Dumazet
2021-01-14 9:29 ` David Laight
2021-01-14 19:00 ` patchwork-bot+netdevbpf
[not found] ` <1617007696.5731978-1-xuanzhuo@linux.alibaba.com>
2021-03-29 9:06 ` Eric Dumazet
2021-03-31 8:11 ` Michael S. Tsirkin
2021-03-31 8:36 ` Eric Dumazet
2021-03-31 8:46 ` Eric Dumazet
2021-03-31 8:49 ` Eric Dumazet
2021-03-31 8:54 ` Eric Dumazet
[not found] ` <1617248264.4993114-2-xuanzhuo@linux.alibaba.com>
2021-04-01 5:06 ` Eric Dumazet
[not found] ` <1617357110.3822439-1-xuanzhuo@linux.alibaba.com>
2021-04-02 12:52 ` Eric Dumazet
2021-04-01 13:51 ` Michael S. Tsirkin
2021-04-01 14:08 ` Eric Dumazet
2021-04-01 7:14 ` Jason Wang
[not found] ` <1617267183.5697193-1-xuanzhuo@linux.alibaba.com>
2021-04-01 9:58 ` Eric Dumazet
2021-04-02 2:52 ` Jason Wang
[not found] ` <1617361253.1788838-2-xuanzhuo@linux.alibaba.com>
2021-04-02 12:53 ` Eric Dumazet
2021-04-06 2:04 ` Jason Wang
[not found] ` <1617190239.1035674-1-xuanzhuo@linux.alibaba.com>
2021-03-31 12:08 ` Eric Dumazet
2021-04-01 13:36 ` Michael S. Tsirkin
2022-09-07 20:19 ` Paolo Abeni
2022-09-07 20:40 ` Eric Dumazet
2022-09-08 10:48 ` Paolo Abeni
2022-09-08 12:20 ` Eric Dumazet
2022-09-08 14:26 ` Paolo Abeni
2022-09-08 16:00 ` Eric Dumazet
2022-09-07 21:36 ` Alexander H Duyck
2022-09-08 11:00 ` Paolo Abeni
2022-09-08 14:53 ` Alexander H Duyck
2022-09-08 18:01 ` Paolo Abeni [this message]
2022-09-08 19:26 ` Alexander Duyck
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