Re: Short question regarding generic_make_request()

[Steffen Persvold <sp@scali.com>]

Ingo Molnar wrote:
> 
> On Mon, 4 Feb 2002, Steffen Persvold wrote:
> 
> > [root@damd1 root]# ping sci4
> > PING sci4 (192.168.4.4) from 192.168.4.3 : 56(84) bytes of data.
> > 64 bytes from sci4 (192.168.4.4): icmp_seq=0 ttl=255 time=238 usec
> 
> > For simplicity I'll say ~200usec. When I change the receive handler
> > from a tasklet to a kernel thread, the numbers look like this :
> >
> > [root@damd1 root]# ping sci4
> > PING sci4 (192.168.4.4) from 192.168.4.3 : 56(84) bytes of data.
> > 64 bytes from sci4 (192.168.4.4): icmp_seq=0 ttl=255 time=4.215 msec
> > 64 bytes from sci4 (192.168.4.4): icmp_seq=1 ttl=255 time=5.728 msec
> 
> this shows some sort of wakeup or softirq handling irregularity. A number
> of softirq latency bugs were fixed, i'd suggest to try this with any
> recent kernel (or recent errata kernel rpms).
> 

You are right indeed. I tried a vanilla 2.4.17 kernel at it performs well with a kernel thread (even
better than a tasklet actually) :

TCP STREAM TEST to sci9
Recv   Send    Send                          
Socket Socket  Message  Elapsed              
Size   Size    Size     Time     Throughput  
bytes  bytes   bytes    secs.    MBytes/sec  

262144 262144 262144    10.00     157.73   


Any idea when this bug was fixed (haven't tried the latest RedHat errata kernel yet, but will do).

I guess now that I can use the kernel thread without loosing performance I can start using
generic_make_request() in the block device server.

Thanks for all the help,

Regards,
-- 
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