Eric Dumazet wrote:

Dave Jones a écrit :

quoted

Just had this bug reported against our development tree..

<snip>

quoted

 > [hans@localhost devel]$ time cat /proc/net/tcp
 > <snip>
 > real    0m0.520s
 > user    0m0.000s
 > sys     0m0.446s
 >  > Thats amazingly slow, esp as I only have 8 tcp connections open.
 >  > Some maybe usefull info: top reports a very high load (50%) from 
soft IRQ's.
 >  > Anyways changing this to a kernel bug.

I wonder why this qualifies as a "kernel bug". This is a well known 
problem.

No its not, /proc/net/tcp may be slow in general but not *this* slow ...

<snip>

Time difference between /proc/net/tcp and netlink on a 4GB x86_64 machine :

# dmesg | grep "TCP established hash"
TCP established hash table entries: 262144 (order: 10, 4194304 bytes)
# time cat /proc/net/tcp >/dev/null

real    0m0.091s
user    0m0.001s
sys     0m0.090s

As quoted above my idle x86_64, using the exact same hash table size, running 
2.6.27-rc2.git1 uses 0.520 seconds for that same command, thats a difference of 
more then a factor 50 !!

This is not about /proc/net/tcp not being fast, this is about it haven gotten 
slower by a factor of 50!

Also notice that this slowdown does not happen on i386.

Anyways I'll try 2.6.27-rc4 and report back with its results.

Regards,

Hans