linux-kernel - Re: [patch] drop epoll max_user_instances and rely only on max_user

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Message-ID: <20090129084210.GA2704@brong.net>
Date:	Thu, 29 Jan 2009 19:42:10 +1100
From:	Bron Gondwana <brong@...tmail.fm>
To:	Davide Libenzi <davidel@...ilserver.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg KH <gregkh@...e.de>, Willy Tarreau <w@....eu>,
	Michael Kerrisk <mtk.manpages@...glemail.com>,
	Bron Gondwana <brong@...tmail.fm>
Subject: Re: [patch] drop epoll max_user_instances and rely only on
	max_user_watches

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.
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