Date: Wed, 18 Jun 2014 18:42:00 -0700
From: Andi Kleen <ak@linux.intel.com>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>, LKML <linux-kernel@vger.kernel.org>,
        Josh Triplett <josh@joshtriplett.org>,
        "Chen, Tim C" <tim.c.chen@intel.com>, Christoph Lameter <cl@linux.com>
Subject: Re: [bisected] pre-3.16 regression on open() scalability
Message-ID: <20140619014200.GO8178@tassilo.jf.intel.com>
References: <539B594C.8070004@intel.com>
 <20140613224519.GV4581@linux.vnet.ibm.com>
 <53A0CAE5.9000702@intel.com>
 <20140618001836.GV4669@linux.vnet.ibm.com>
 <53A132D4.60408@intel.com>
 <20140618125831.GB4669@linux.vnet.ibm.com>
 <53A1CE19.7040103@intel.com>
 <20140618203052.GT4669@linux.vnet.ibm.com>
 <20140618235131.GA25946@linux.vnet.ibm.com>
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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@linux.intel.com -- Speaking for myself only
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