linux-kernel - Re: aio: questions with ioctx_alloc() and large num_possible

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Message-Id: <a2a7cac6-30dd-7d73-6a0a-5cd602a01b33@linux.vnet.ibm.com>
Date:   Wed, 5 Oct 2016 16:22:02 -0300
From:   Mauricio Faria de Oliveira <mauricfo@...ux.vnet.ibm.com>
To:     Benjamin LaHaise <bcrl@...ck.org>
Cc:     Kent Overstreet <kent.overstreet@...il.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, linux-aio@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: aio: questions with ioctx_alloc() and large num_possible_cpus()

Ben,

On 10/05/2016 03:17 PM, Benjamin LaHaise wrote:
> Anything's possible when a local user can run code. [snip]  That
> said, local users tend not to DoS themselves.

Agree. I thought of something that could be particularly related to
the aio implementation; but I guess there's nothing so special then.

> [snip] It probably makes
> sense to implement per-user limits rather than the current global limit,
> and maybe even convert them to an rlimit to better fit in with the
> available frameworks for managing these things.

I see it would be a nice improvement, but unfortunately that's not a
task that I can take at the moment. For now, the most I'm able to do
is to continue to try to understand whether there's something we can
do that may help the small nr_events case to be more on par with the
large nr_events case.. or any other beginner-level fixes to the area. :)

Thanks again,

-- 
Mauricio Faria de Oliveira
IBM Linux Technology Center