Re: pipe and af/unix latency differences between aa and jam on smp

["J.A. Magallon" <jamagallon@able.es>]

On 2002.07.09 rwhron@earthlink.net wrote:
>The -jam patchset is interesting because it starts out
>with the entire -aa patchset and adds a few things.
>
>Sometimes small differences in LMbench between -jam and -aa are 
>just CPU bounces on SMP.  The difference for pipe and af/unix latency
>only appears on SMP too, but it is very consistent.  (My k6/2
>has small differences between -aa and -jam for pipe and af/unix
>latency).
>
>You will know better what could make the difference:
>
>This is the averages:
>
>*Local* Communication latencies in microseconds - smaller is better
>-------------------------------------------------------------------
>kernel              Pipe    AF/Unix
>-----------------  -------  -------
>2.4.19-pre10-aa4    33.941   70.216
>2.4.19-pre10-jam2    7.877   16.699
>

I took a look at your numbers:

*Local* Communication latencies in microseconds - smaller is better
-------------------------------------------------------------------
kernel                          Pipe    AF/Unix    UDP    RPC/UDP    TCP    RPC/TCP  TCPconn
-----------------------------  -------  -------  -------  -------  -------  -------  -------
2.4.19-pre7-jam6                29.513   42.369  58.6165  60.7792  50.2572  82.4976   87.321
2.4.19-pre8-jam2                 7.697   15.274  59.6730  60.8190   55.276  82.1297   89.416
2.4.19-pre8-jam2-nowuos          7.739   14.929  57.9326  60.5497  55.9745  81.8908   90.370

(last line says that wake-up-sync is not responsible...)

Main changes between first two were irqbalance and ide6->ide10.


-- 
J.A. Magallon             \   Software is like sex: It's better when it's free
mailto:jamagallon@able.es  \                    -- Linus Torvalds, FSF T-shirt
Linux werewolf 2.4.19-rc1-jam2, Mandrake Linux 8.3 (Cooker) for i586
gcc (GCC) 3.1.1 (Mandrake Linux 8.3 3.1.1-0.7mdk)