On Thu, 1 Mar 2007 12:30:50 +0100 Eric Dumazet <dada1@xxxxxxxxxxxxx> wrote: > On Wednesday 28 February 2007 17:07, John wrote: > > > > > Consider an idle Linux 2.6.20-rt8 system, equipped with a single PCI-E > > gigabit Ethernet NIC, running on a modern CPU (e.g. Core 2 Duo E6700). > > All this system does is time stamp 1000 packets per second. > > > > Are you claiming that this platform *cannot* handle most packets within > > less than 1 microsecond of their arrival? > > Yes I claim it. > > You expect too much of this platform, unless "most" means 10 % for > you ;) > > If you replace "1 us" by "50 us", then yes, it probably can do it, if "most" > means 99%, (not 99.999 %) > > Anyway, if you want to play, you can apply this patch on top of > linux-2.6.21-rc2 (nanosecond resolution infrastruture needs 2.6.21) > I let you do the adjustments for rt kernel. > > I compiled it on my i386 machine, and tested it with a patched libpcap/tcpdump > > [PATCH] NET : introduce nanosecond time infrastructure and SIOCGSTAMPNS > > It appears some machines are *really* fast and that micro second resolution is > a limiting factor. > > This patch converts sk_buff timestamp to use new nanosecond infra (added in > 2.6.21), and introduces a new ioctl SIOCGSTAMPNS to let applications access > nanosecond resolution (ie a timespec instead of timeval) > > > Signed-off-by: Eric Dumazet <dada1@xxxxxxxxxxxxx> > You probably want to add a SO_TIMESTAMPNS setsockopt() value like existing SO_TIMESTAMP Also use NSEC_PER_USEC rather than hardcoded 1000. -- Stephen Hemminger <shemminger@xxxxxxxxxxxxxxxxxxxx> - To unsubscribe from this list: send the line "unsubscribe linux-net" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
