linux-kernel - Re: [bisected] pre-3.16 regression on open() scalability

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Message-ID: <20140619014200.GO8178@tassilo.jf.intel.com>
Date:	Wed, 18 Jun 2014 18:42:00 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Dave Hansen <dave.hansen@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Josh Triplett <josh@...htriplett.org>,
	"Chen, Tim C" <tim.c.chen@...el.com>,
	Christoph Lameter <cl@...ux.com>
Subject: Re: [bisected] pre-3.16 regression on open() scalability

I still think it's totally the wrong direction to pollute so 
many fast paths with this obscure debugging check workaround
unconditionally.

cond_resched() is in EVERY sleeping lock and in EVERY memory allocation!
And these are really critical paths for many workloads.

If you really wanted to do this I think you would first need
to define a cond_resched_i_am_not_fast() or somesuch.

Or put it all behind some debugging ifdef.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only
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