From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <dada1@cosmosbay.com>
Subject: Re: Network latency regressions from 2.6.22 to 2.6.29 (results with
 IRQ affinity)
Date: Mon, 20 Apr 2009 23:52:30 +0200
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Cc: David Miller <davem@davemloft.net>,
	Michael Chan <mchan@broadcom.com>,
	Ben Hutchings <bhutchings@solarflare.com>,
	netdev@vger.kernel.org
To: Christoph Lameter <cl@linux.com>
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Christoph Lameter a =E9crit :
> On Mon, 20 Apr 2009, Eric Dumazet wrote:
>=20
>> No changes in udpping but noise.
>=20
> No changes in the results of udpping that you would not consider nois=
e?

Only changes where when every cpus played, so it really is not meaningf=
ull.

>=20
> The time syscalls are virtual syscalls which are quite cheap.

Not on 32bits afaik, with glibc I use at least, strace told me.

clock_gettime(CLOCK_REALTIME, {1240262824, 400770067}) =3D 0
sendto(3, "\314\335\356\377\300\250\24p#)\0\0\23\324\207\264\377\377\37=
7\377\0\1\2\3\4\5\6\7\10\t\0\0\3"..., 300, 0, {sa_family=3DAF_INET, sin=
_port=3Dhtons(9000), sin_addr=3Dinet_addr("192.168.20.112")}, 16) =3D 3=
00
recvfrom(3, "\314\335\356\377\300\250\24p#)\0\0\23\324\207\264\377\377\=
377\377\0\1\2\3\4\5\6\7\10\t\0\0\3"..., 300, 0, NULL, NULL) =3D 300
clock_gettime(CLOCK_REALTIME, {1240262824, 401108324}) =3D 0
clock_gettime(CLOCK_REALTIME, {1240262824, 401177464}) =3D 0

cost is about 384 ns on this 32bits 3GHz machine (without strace), whil=
e its 51 ns on 64 bit

Anyway I'll try to boot 64bit kernels on those 32bit distro machines in=
 following days...