Re: [patch] drop epoll max_user_instances and rely only on max_user_watches

[Bron Gondwana <brong@fastmail.fm>]

On Wed, Jan 28, 2009 at 08:56:07PM -0800, Davide Libenzi wrote:
> Linus suggested to put limits where the money is, and max_user_watches 
> already does that w/out the need of max_user_instances. That has the 
> advantage to mitigate the potential DoS while allowing pretty generous 
> default behavior.
> Allowing top 4% of low memory (per user) to be allocated in epoll 
> watches, we have:
> 
> LOMEM    MAX_WATCHES (per user)
> 512MB    ~178000
> 1GB      ~356000
> 2GB      ~712000
> 
> A box with 512MB of lomem, will meet some challenge in hitting 180K 
> watches, socket buffers math teaches us.
> No more max_user_instances limits then.

Excellent.  Glad to see :)  Saves me from keeping on working on my "only
account epoll within epoll for max_user_instances" patch, which would
have just been needless complexity (though cheap - is_file_epoll looks
pretty easy to check for both descriptors) - and I hadn't even compiled
and tested it yet.

Thanks Davide - this will keep our mxes humming along happily.

Bron.