netdev - Re: CLOCK_MONOTONIC datagram timestamps by the kernel

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Message-Id: <200703011230.50596.dada1@cosmosbay.com>
Date:	Thu, 1 Mar 2007 12:30:50 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	John find <linux.kernel@...e.fr>
Cc:	linux-net@...r.kernel.org, netdev@...r.kernel.org,
	Stephen Hemminger <shemminger@...ux-foundation.org>
Subject: Re: CLOCK_MONOTONIC datagram timestamps by the kernel

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@...mosbay.com>

 fs/compat_ioctl.c                       |   17 ++++++++
 include/asm-alpha/sockios.h             |    1 
 include/asm-arm26/sockios.h             |    3 +
 include/asm-avr32/sockios.h             |    3 +
 include/asm-cris/sockios.h              |    3 +
 include/asm-frv/sockios.h               |    3 +
 include/asm-h8300/sockios.h             |    3 +
 include/asm-i386/sockios.h              |    3 +
 include/asm-ia64/sockios.h              |    3 +
 include/asm-m32r/sockios.h              |    3 +
 include/asm-m68k/sockios.h              |    3 +
 include/asm-mips/sockios.h              |    3 +
 include/asm-parisc/sockios.h            |    3 +
 include/asm-powerpc/sockios.h           |    3 +
 include/asm-s390/sockios.h              |    3 +
 include/asm-sh/sockios.h                |    1 
 include/asm-sh64/sockios.h              |    1 
 include/asm-sparc/sockios.h             |    3 +
 include/asm-sparc64/sockios.h           |    3 +
 include/asm-v850/sockios.h              |    3 +
 include/asm-x86_64/sockios.h            |    3 +
 include/asm-xtensa/sockios.h            |    3 +
 include/linux/skbuff.h                  |   42 +++++++++++++++-------
 include/net/compat.h                    |    1 
 include/net/sock.h                      |   16 +++++---
 net/appletalk/ddp.c                     |    3 +
 net/atm/ioctl.c                         |    3 +
 net/ax25/af_ax25.c                      |    4 ++
 net/bridge/netfilter/ebt_ulog.c         |    2 -
 net/compat.c                            |   31 +++++++++++++---
 net/core/dev.c                          |   14 +++----
 net/core/skbuff.c                       |    4 +-
 net/core/sock.c                         |   28 +++++++++++---
 net/econet/af_econet.c                  |    4 +-
 net/ipv4/af_inet.c                      |    3 +
 net/ipv4/ip_fragment.c                  |    6 +--
 net/ipv4/tcp_output.c                   |    2 -
 net/ipv6/af_inet6.c                     |    3 +
 net/ipv6/netfilter/nf_conntrack_reasm.c |    6 +--
 net/ipv6/reassembly.c                   |    6 +--
 net/ipx/af_ipx.c                        |    2 -
 net/netrom/af_netrom.c                  |    5 ++
 net/packet/af_packet.c                  |    8 ++--
 net/rose/af_rose.c                      |    2 +
 net/sunrpc/svcsock.c                    |    9 ++--
 net/wanrouter/af_wanpipe.c              |    3 +
 net/x25/af_x25.c                        |   12 ++++++
 47 files changed, 216 insertions(+), 77 deletions(-)


View attachment "net_nanosec_stamp.patch" of type "text/plain" (31833 bytes)