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

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Date:   Wed, 5 Oct 2016 14:58:12 -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()

Hi Benjamin,

On 10/05/2016 02:41 PM, Benjamin LaHaise wrote:
> I'd suggest increasing the default limit by changing how it is calculated.
> The current number came about 13 years ago when machines had orders of
> magnitude less RAM than they do today.

Thanks for the suggestion.

Does the default also have implications other than memory usage?
For example, concurrency/performance of as much aio contexts running,
or if userspace could try to exploit some point with a larger number?

Wondering about it because it can be set based on num_possible_cpus(),
but that might be really large on high-end systems.

Regards,

-- 
Mauricio Faria de Oliveira
IBM Linux Technology Center