> Subject: Re: Linux 2.2.2 TCP delays every 41st small packet by 10-20 ms
> Andrea Arcangeli wrote:
> > On Thu, 25 Feb 1999, Josip Loncaric wrote:
> >
> > >The conclusion is this: in Linux TCP, every N-th small packet is delayed
> > >by 1-2 "jiffies" (defined by the 100 Hz system clock). For Linux kernel
> >
> > This 1-2 jiffies made me thing again at the PSH thing. Probably I am
> > completly out but could you try this patch?
>
> Your patch improved things by a factor of 20. The easiest way for me to
...
> Atypically large delays now cluster around 1 millisecond instead of 20
> milliseconds. In both cases, a vast majority of the messages are spaced
> by less than 100 microseconds. Even after the patch, five delays of 200
> milliseconds out of the 420,602 measured were seen, but this might be
> due to some unavoidable system activity during the test.
Could you please try the following?
Bump the RX_RING_SIZE and TX_RING_SIZE in the driver up to 128 or 256
entries each. With enough memory this should have trivial free memory
impact and remove any queue-limit noise in the measurments.
This should have no significant average performance impact.
If it does, there is something unexpected going on.
Donald Becker becker@cesdis.gsfc.nasa.gov
USRA-CESDIS, Center of Excellence in Space Data and Information Sciences.
Code 930.5, Goddard Space Flight Center, Greenbelt, MD. 20771
301-286-0882 http://cesdis.gsfc.nasa.gov/people/becker/whoiam.html
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