From: Wei Liu <wei.liu2@citrix•com>
To: David Laight <David.Laight@ACULAB•COM>
Cc: 'Wei Liu' <wei.liu2@citrix•com>,
Stefan Bader <stefan.bader@canonical•com>,
Zoltan Kiss <zoltan.kiss@citrix•com>,
Eric Dumazet <eric.dumazet@gmail•com>,
"netdev@vger•kernel.org" <netdev@vger•kernel.org>,
"xen-devel@lists•xen.org" <xen-devel@lists•xen.org>,
David Vrabel <david.vrabel@citrix•com>,
Konrad Wilk <konrad.wilk@oracle•com>,
Boris Ostrovsky <boris.ostrovsky@oracle•com>
Subject: Re: [PATCH net-next] xen-netfront: try linearizing SKB if it occupies too many slots
Date: Fri, 30 May 2014 13:35:54 +0100 [thread overview]
Message-ID: <20140530123554.GD2655@zion.uk.xensource.com> (raw)
In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D172506AE@AcuExch.aculab.com>
On Fri, May 30, 2014 at 12:28:53PM +0000, David Laight wrote:
> From: Wei Liu
> > On Fri, May 30, 2014 at 10:06:48AM +0200, Stefan Bader wrote:
> > [...]
> > > I had been idly wondering about this onwards. And trying to understand the whole
> > > skb handling environment, I tried to come up with some idea as well. It may be
> > > totally stupid and using the wrong assumptions. It seems to work in the sense
> > > that things did not blow up into my face immediately and somehow I did not see
> > > dropped packages due to the number of slots either.
> > > But again, I am not sure I am doing the right thing. The idea was to just try to
> > > get rid of so many compound pages (which I believe are the only ones that can
> > > have an offset big enough to allow some alignment savings)...
> > >
> > > -Stefan
> > >
> >
> > Thanks. I think the general idea is OK, but it still involves
> > unnecessary page allocation. We don't actually need to get rid of
> > compound page by replacing it with a new page, we just need to make sure
> > the data inside is aligned.
> >
> > If you look at xennet_make_frags, it only grants the 4K page which
> > contains data. I presume a simple memove would be better than alloc_page
> > + memcpy. What do you think?
> >
> > Like:
> > memmove(page_address(fpage), page_address(fpage)+offset, size);
> > frag->page_offset = 0;
>
> Isn't the rest of the page likely to contain fragments of other ethernet
> frames? Even possibly of other data?
>
You're right, this is a valid concern.
prev parent reply other threads:[~2014-05-30 12:35 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-16 11:08 [PATCH net-next] xen-netfront: try linearizing SKB if it occupies too many slots Wei Liu
2014-05-16 13:04 ` Eric Dumazet
2014-05-16 13:11 ` Wei Liu
2014-05-16 14:21 ` Eric Dumazet
2014-05-16 14:36 ` Wei Liu
2014-05-16 15:22 ` Eric Dumazet
2014-05-16 15:34 ` Wei Liu
2014-05-16 16:29 ` Zoltan Kiss
2014-05-16 16:47 ` Eric Dumazet
2014-05-16 16:51 ` Zoltan Kiss
2014-05-16 17:00 ` Eric Dumazet
2014-05-16 16:54 ` Wei Liu
2014-05-19 16:47 ` Zoltan Kiss
2014-05-30 8:06 ` Stefan Bader
2014-05-30 12:07 ` Zoltan Kiss
2014-05-30 12:37 ` Stefan Bader
2014-07-02 12:23 ` Stefan Bader
2014-07-02 13:12 ` Zoltan Kiss
2014-05-30 12:11 ` Wei Liu
2014-05-30 12:28 ` Stefan Bader
2014-05-30 12:38 ` Wei Liu
2014-05-30 12:28 ` David Laight
2014-05-30 12:35 ` Wei Liu [this message]
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