From: David Laight <David.Laight@ACULAB•COM>
To: 'Eric Dumazet' <edumazet@google•com>
Cc: Eric Dumazet <eric.dumazet@gmail•com>,
"David S . Miller" <davem@davemloft•net>,
Jakub Kicinski <kuba@kernel•org>, netdev <netdev@vger•kernel.org>,
Alexander Duyck <alexanderduyck@fb•com>,
"Paolo Abeni" <pabeni@redhat•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, 14 Jan 2021 09:29:23 +0000 [thread overview]
Message-ID: <787e2b85cd2f4f0f90d7fe871dce85ff@AcuMS.aculab.com> (raw)
In-Reply-To: <CANn89iKS-J8BzMd+_PmFV67C+3hPx-C0saY0yFMdDWfHPwazHQ@mail.gmail.com>
From: Eric Dumazet
> Sent: 14 January 2021 05:17
>
> On Wed, Jan 13, 2021 at 11:23 PM David Laight <David.Laight@aculab•com> wrote:
> >
> > From: Eric Dumazet
> > > Sent: 13 January 2021 16:18
> > >
> > > From: Eric Dumazet <edumazet@google•com>
> > >
> > > Both virtio net and napi_get_frags() allocate skbs
> > > with a very small skb->head
> > >
> > > While using page fragments instead of a kmalloc backed skb->head might give
> > > a small performance improvement in some cases, there is a huge risk of
> > > under estimating memory usage.
> >
> > There is (or was last time I looked) also a problem with
> > some of the USB ethernet drivers.
> >
> > IIRC one of the ASXnnnnnn (???) USB3 ones allocates 64k skb to pass
> > to the USB stack and then just lies about skb->truesize when passing
> > them into the network stack.
>
> You sure ? I think I have fixed this at some point
>
> https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=a9e0aca4b37885b5599e52211f09
> 8bd7f565e749
I might have forgotten that patch :-)
Or possibly only remembered it changing small packets.
> > The USB hardware will merge TCP receives and put multiple ethernet
> > packets into a single USB message.
> > But single frames can end up in very big kernel memory buffers.
> >
>
> Yeah, this is a known problem.
The whole USB ethernet block is somewhat horrid and inefficient
especially for XHCI/USB3 - which could have high speed ethernet.
It really needs to either directly interface to the XHCI ring
(like a normal ethernet driver) or be given the sequence of
USB rx packets to split/join into ethernet frames.
However I don't have the time to make those changes.
When I was looking at that driver 'dayjob' was actually
trying to make it work.
They dropped that idea later.
I've not got the ethernet dongle any more either.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2021-01-14 9:31 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 [this message]
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
[not found] ` <1617190239.1035674-1-xuanzhuo@linux.alibaba.com>
2021-03-31 12:08 ` Eric Dumazet
2021-04-01 13:36 ` Michael S. Tsirkin
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
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
2022-09-08 19:26 ` Alexander Duyck
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