Re: v6: faster tree-based sysctl implementation

On Tue, Dec 6, 2011 at 4:11 PM, Anca Emanuel [off-list ref] wrote:

time modprobe dummy numdummies=1000FATAL: Error inserting dummy
(/lib/modules/3.2.0-3-generic/kernel/drivers/net/dummy.ko): Operation
not permitted

Generally when you get "Operation not permitted" you should try with sudo.
This is the man-page: http://xkcd.com/149/ :)

What are the practical problems you solve with this ?
Name one or more.

Sysctl uses a slow algorithm: O(N^2) for insertions, O(N) for lookup,
with a relatively big constant.
The performance is acceptable when N is small, but sometimes it can
grow to bigger values.
One case where N can grow to very large values is when you add network
interfaces.

Some companies (like IXIACOM which sponsored this work at the
beginning of this year) have use-cases in which they need 10^3..10^6
network interfaces. The current sysctl implementation is unacceptable
for them.

@Damien Millescamps might have some input on where he needs better
sysctl performance as he prompted me to re-send this patch series.

This algorithm is O(N * logN) for insert and O(logN) for lookup.

You add more code. This is not good. If you reduce the code, then it
will be interesting.

Thank you. I know that, but it's easier said than done. I'd welcome
some feedback in what could be simplified in my patches :)

-- 
 .
..: Lucian