Date: Wed, 22 May 2013 16:55:51 -0700 From: Adrian Chadd <adrian@freebsd.org> To: Luigi Rizzo <luigi@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r250911 - head/sys/kern Message-ID: <CAJ-Vmons5-4-nqa-yG0aLOqqzRgMuhpgY4PYD1Xgk8J4su5fog@mail.gmail.com> In-Reply-To: <201305221632.r4MGWIjK069433@svn.freebsd.org> References: <201305221632.r4MGWIjK069433@svn.freebsd.org>
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Odd, this reads like one of those things that's better off being time-capped, rather than packet-count capped. Good find, though. Adrian On 22 May 2013 09:32, Luigi Rizzo <luigi@freebsd.org> wrote: > Author: luigi > Date: Wed May 22 16:32:18 2013 > New Revision: 250911 > URL: http://svnweb.freebsd.org/changeset/base/250911 > > Log: > Increase the (arbitrary) limit for the number of packets per tick > from 1k to 20k The previous value was good 10 years ago, but not > anymore now. > > More importantly, lots of good surprises: > polling is incredibly effective under virtualization, and not only > prevents livelock but also saves most of the VM exit overhead in > receive mode. > > Using polling, a FreeBSD instance under qemu-kvm remains perfectly > responsive even when bombed with 10 Mpps over an emulated e1000, > and happily processes 1.7 Mpps through ipfw. > > Note that some incompatibilities still remain: e.g. polling is not > (yet) compatible with netmap, and seems to freeze the guest when > kern.polling.idle_poll=1 > > MFC after: 3 days > > Modified: > head/sys/kern/kern_poll.c > > Modified: head/sys/kern/kern_poll.c > ============================================================================== > --- head/sys/kern/kern_poll.c Wed May 22 15:15:05 2013 (r250910) > +++ head/sys/kern/kern_poll.c Wed May 22 16:32:18 2013 (r250911) > @@ -87,12 +87,11 @@ static struct mtx poll_mtx; > * The following constraints hold > * > * 1 <= poll_each_burst <= poll_burst <= poll_burst_max > - * 0 <= poll_each_burst > * MIN_POLL_BURST_MAX <= poll_burst_max <= MAX_POLL_BURST_MAX > */ > > #define MIN_POLL_BURST_MAX 10 > -#define MAX_POLL_BURST_MAX 1000 > +#define MAX_POLL_BURST_MAX 20000 > > static uint32_t poll_burst = 5; > static uint32_t poll_burst_max = 150; /* good for 100Mbit net and HZ=1000 */
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