Re: Gigabit Performance 2.4.19-preX - Excessive locks, calls, waits

From: Jeff V. Merkey (jmerkey@vger.timpanogas.org)
Date: Mon Mar 04 2002 - 12:46:09 EST


On Mon, Mar 04, 2002 at 03:04:00PM +0000, Alan Cox wrote:
> > provided for review. Recommend a minumum change of increasing
> > the sysctl_hot_list_len from 128 to 1024 by default. I have reviewed
>
> Good way to kill low end boxes. It probably wants sizing based on system
> size and load monitoring.
>
> > NetWare always created ECB's (Event Control Blocks) at the max size
> > of the network adpapter rather than trying to allocate fragment
> > elements on the fly the way is being done in Linux with skb's.
>
> Thats up to the network adapter. In fact the Linux drivers mostly do
> keep preloaded with full sized buffers and only copy if the packet size
> is small (and copying 1 or 2 cache lines isnt going to hurt anyone)

There's an increase in latency. For my application, I have no
problem keeping around a local patch that corrects this behavior
if folks don't feel it needs fixing. From everything I've ever
done in this space, having needless alloc/free calls in a
performance intensive path that requires low latency like a Lan
driver is not a good thing.

I am idle most of the time since I have eliminated all of the
copy activity by using SCI in the system. This is why it's
idle most of the time. Were I using the IP stack code in Linux
proper, the utilization would be through the roof.

:-)

Jeff

>
> > 28044 default_idle 584.2500
>
> You spent most of your time asleep 8)
>
> > 1117 __rdtsc_delay 34.9062
>
> Or doing delays
>
> > 927 eth_type_trans 4.4567
>
> And pulling a line into L1 cache
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