linux-kernel - Re: [RFC PATCH-tip v2 5/6] locking/rwsem: Change RWSEM_WAITING

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Message-ID: <20160615174348.GT30921@twins.programming.kicks-ass.net>
Date:	Wed, 15 Jun 2016 19:43:48 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Waiman Long <Waiman.Long@....com>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, linux-alpha@...r.kernel.org,
	linux-ia64@...r.kernel.org, linux-s390@...r.kernel.org,
	linux-arch@...r.kernel.org, Davidlohr Bueso <dave@...olabs.net>,
	Jason Low <jason.low2@...com>,
	Dave Chinner <david@...morbit.com>,
	Scott J Norton <scott.norton@....com>,
	Douglas Hatch <doug.hatch@....com>
Subject: Re: [RFC PATCH-tip v2 5/6] locking/rwsem: Change RWSEM_WAITING_BIAS
 for better disambiguation

On Tue, Jun 14, 2016 at 06:48:08PM -0400, Waiman Long wrote:
> even the reduced maximum of about 16k (32-bit) or 1G (64-bit) should
> be more than enough for the foreseeable future.

So what happens if I manage to create 16k+ threads on my 32bit kernel
and get them all to do mmap() or so at the same time.

That doesn't seem too far fetched.

Then again, with double that (the current limit) that doesn't seem
impossible either.