netdev.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Eric Dumazet <eric.dumazet-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Ming Lei <tom.leiming-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: "Ben Hutchings"
	<bhutchings-s/n/eUQHGBpZroRs9YW3xA@public.gmane.org>,
	"Oliver Neukum" <oliver-GvhC2dPhHPQdnm+yROfE0A@public.gmane.org>,
	"Grant Grundler"
	<grundler-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	"Freddy Xin" <freddy-knRN6Y/kmf1NUHwG+Fw1Kw@public.gmane.org>,
	"David Miller" <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>,
	netdev <netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"ASIX Louis [蘇威陸]"
	<louis-knRN6Y/kmf1NUHwG+Fw1Kw@public.gmane.org>,
	"Allan Chou" <allan-knRN6Y/kmf1NUHwG+Fw1Kw@public.gmane.org>
Subject: Re: [PATCH 1/1] TX throttling bug-fixing patch of AX88179_178A
Date: Thu, 25 Jul 2013 04:01:41 -0700	[thread overview]
Message-ID: <1374750101.23313.16.camel@edumazet-glaptop> (raw)
In-Reply-To: <CACVXFVNyFk0Zpi4tC0ENiq8RcrtrjYW-Dhs+A56+Pw4BKm8y8A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On Thu, 2013-07-25 at 13:25 +0800, Ming Lei wrote:
> On Thu, Jul 25, 2013 at 1:10 PM, Eric Dumazet <eric.dumazet-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > On Thu, 2013-07-25 at 10:28 +0800, Ming Lei wrote:
> >
> >>
> >> It depends if size of sg buffer(except for last one) in the sg list can be
> >> divided by usb endpoint's max packet size(512 or 1024), at least there
> >> is the constraint:
> >>
> >> http://git.kernel.org/cgit/linux/kernel/git/gregkh/usb.git/commit/?h=usb-next&id=10e232c597ac757e7f8600649f7e872e86de190f
> >>
> >> I am wondering if network stack can meet that.  If not, it might be a
> >> bit difficult
> >> because lots of USB host controller don't support that, and driver may have
> >> to support SG and non-SG at the same time for working well on all HCs.
> >
> > I do not see the problem.
> >
> > If one skb has 2 fragments of 32KB, couldn't they be split into 64 1K
> > segments by the device driver ?
> 
> OK, if length of fragments of all SKBs from network stack can always guarantee
> to be divided by 1024, that is fine,  seems I worry about too much, :-)

Unfortunately, there is no such guarantee. TSO permits sendfile() zero
copy operation, so the frags can be of any size, any offset...

In this mode, the first element (skb->head) will typically contains the
headers, and there are way below 512 bytes.

So even with lowering netdev->gso_max_size under PAGE_SIZE, most of the
packets will need to be copied into a single segment.



--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

  parent reply	other threads:[~2013-07-25 11:01 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-20  9:16 freddy
2013-07-22 17:07 ` Eric Dumazet
2013-07-22 17:11   ` Ben Hutchings
2013-07-22 18:29   ` Grant Grundler
2013-07-22 18:38     ` Ben Hutchings
2013-07-22 18:47       ` Eric Dumazet
2013-07-22 19:47         ` Ben Hutchings
     [not found]           ` <1374522471.1635.48.camel-/LGg1Z1CJKQ+9kgCwbf1HqK4ta4zdZpAajtMo4Cw6ucAvxtiuMwx3w@public.gmane.org>
2013-07-23  6:10             ` Eric Dumazet
2013-07-23 23:46               ` David Miller
2013-07-23 23:56                 ` Eric Dumazet
2013-07-24  0:05                   ` Eric Dumazet
2013-07-24  0:15                     ` [PATCH] usbnet: do not pretend to support SG/TSO Eric Dumazet
2013-07-26 20:48                       ` David Miller
2013-07-24  0:17                     ` [PATCH 1/1] TX throttling bug-fixing patch of AX88179_178A David Miller
2013-07-24  2:29                 ` Grant Grundler
     [not found]                   ` <CANEJEGtLavwdPdq_Qojz_x-DQ3KXfZp0vPYr6imKtNxN0Hf_2Q-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-07-24  2:32                     ` Grant Grundler
2013-07-25  2:28               ` Ming Lei
2013-07-25  5:10                 ` Eric Dumazet
2013-07-25  5:25                   ` Ming Lei
     [not found]                     ` <CACVXFVNyFk0Zpi4tC0ENiq8RcrtrjYW-Dhs+A56+Pw4BKm8y8A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-07-25 11:01                       ` Eric Dumazet [this message]
2013-07-25 14:52                         ` Ming Lei
2013-07-25 15:00                           ` Ben Hutchings
     [not found]                           ` <CACVXFVNre5SsJhaVqFNRcop7ahqxabWqHZkjBZccj1ZqOAUZ9A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-07-25 15:11                             ` Eric Dumazet
2013-07-25 13:34                     ` Ben Hutchings

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=1374750101.23313.16.camel@edumazet-glaptop \
    --to=eric.dumazet-re5jqeeqqe8avxtiumwx3w@public.gmane.org \
    --cc=allan-knRN6Y/kmf1NUHwG+Fw1Kw@public.gmane.org \
    --cc=bhutchings-s/n/eUQHGBpZroRs9YW3xA@public.gmane.org \
    --cc=davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org \
    --cc=freddy-knRN6Y/kmf1NUHwG+Fw1Kw@public.gmane.org \
    --cc=grundler-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org \
    --cc=linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
    --cc=linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
    --cc=louis-knRN6Y/kmf1NUHwG+Fw1Kw@public.gmane.org \
    --cc=netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
    --cc=oliver-GvhC2dPhHPQdnm+yROfE0A@public.gmane.org \
    --cc=tom.leiming-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org \
    --subject='Re: [PATCH 1/1] TX throttling bug-fixing patch of AX88179_178A' \
    /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).