Re: [PATCH] hashed device lookup (New Benchmarks)

[Ben Greear]

Andi Kleen wrote:
> 
> On Mon, Jan 08, 2001 at 04:23:41PM +0100, Ben Greear wrote:
> > I don't argue that ifconfig shouldn't be fixed, but the hash speeds up
> 
> It's already fixed since months. There was one stupid algorithm, which
> I was to blame for when I changed ifconfig to use a device list two years ago.

The benchmark was run against this one:
[root@candle lanforge]# ifconfig --version
net-tools 1.57
ifconfig 1.40 (2000-05-21)

The latest I could find anywhere....  Please tell me the version of a
newer one if it exists.

> > ip by about 2X too.  Is that not useful enough?  ip seems to be implemented
> > pretty efficient, so if the hash helps it significantly then maybe it
> > can help other efficient programs too.  Notice that it is the system
> > (ie kernel) time that stays remarkably flat with the hash + ip graph.
> 
> Just does your benchmark represent anything that real users do frequently ?

I'm going to write something that binds to a raw device, which is something
users (DHCP, for sure) does.  If it does not show any significant improvement,
then I'll drop the issue untill many-many interfaces are more common.

> 
> If you really want to optimize I'm sure there are lots of areas in the kernel
> where your efforts are better spent ;) [just run with a the kernel profiler on
> for a few days on your box and look at all the real hot spots]

I was just trying to smooth VLAN's adoption into the kernel by removing the
one linear-lookup that I know of relating to lots of VLANs.  It obviously
isn't horribly important, but it was fun :)

> 
> BTW, if you just want to optimize ip link ls speed it would be probably enough
> to keep a one behind cache that just caches the next member after the last
> search.

That is still linear in the kernel...or do you mean cache in the kernel?  At any
rate, I'm more concerned about random access.

> 
> -Andi

-- 
Ben Greear ([e-mail])  http://www.candelatech.com
Author of ScryMUD:  scry.wanfear.com 4444        (Released under GPL)
http://scry.wanfear.com               http://scry.wanfear.com/~greear