netdev - Re: [PATCH 0/4] [RFC] virtio-net: Improve small packet performance

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 5 May 2011 15:13:43 +0530
From:	Krishna Kumar2 <krkumar2@...ibm.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	davem@...emloft.net, eric.dumazet@...il.com, kvm@...r.kernel.org,
	netdev@...r.kernel.org, rusty@...tcorp.com.au
Subject: Re: [PATCH 0/4] [RFC] virtio-net: Improve small packet performance

"Michael S. Tsirkin" <mst@...hat.com> wrote on 05/05/2011 02:34:39 PM:

> > It shows that 2.9% of the time, the 1 jiffy was not enough
> > to free up space in the txq.
>
> How common is it to free up space in *less than* 1 jiffy?

True, but the point is that the space freed is just
enough for 43 entries, keeping it lower means a flood
of (psuedo) stop's and restart's.

> > That could also mean that we
> > had set xmit_restart just before jiffies changed. But the
> > average free capacity when we *resumed* xmits is:
> > Sum of slots / (Good + Bad) = 43.
> >
> > So the delay of 1 jiffy helped the host clean up, on average,
> > just 43 entries, which is 16% of total entries. This is
> > intended to show that the guest is not sitting idle waiting
> > for the jiffy to expire.
>
> OK, nice, this is exactly what my patchset is trying
> to do, without playing with timers: tell the host
> to interrupt us after 3/4 of the ring is free.
> Why 3/4 and not all of the ring? My hope is we can
> get some parallelism with the host this way.
> Why 3/4 and not 7/8? No idea :)
>
> > > > > I can post it, mind testing this?
> > > >
> > > > Sure.
> > >
> > > Just posted. Would appreciate feedback.
> >
> > Do I need to apply all the patches and simply test?
> >
> > Thanks,
> >
> > - KK
>
> Exactly. You can also try to tune the threshold
> for interrupts as well.

Could you send me (privately) the entire virtio-net/vhost
patch in a single file? It will help me quite a bit :)
Either attachment or inline is fine.

thanks,

- KK

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