From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Andi Kleen <ak@linux.intel.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
Date: Wed, 18 Jun 2014 19:13:37 -0700 [thread overview]
Message-ID: <20140619021337.GA4669@linux.vnet.ibm.com> (raw)
In-Reply-To: <20140619014200.GO8178@tassilo.jf.intel.com>
On Wed, Jun 18, 2014 at 06:42:00PM -0700, Andi Kleen wrote:
>
> I still think it's totally the wrong direction to pollute so
> many fast paths with this obscure debugging check workaround
> unconditionally.
OOM prevention should count for something, I would hope.
> 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.
My first thought was to put it behind CONFIG_NO_HZ_FULL, but everyone
seems to be enabling that one.
As mentioned earlier, I could potentially push the check behind
the need-resched check, which would get it off of the common case
of the code paths you call out above.
Thanx, Paul
next prev parent reply other threads:[~2014-06-19 2:13 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-13 20:04 [bisected] pre-3.16 regression on open() scalability Dave Hansen
2014-06-13 22:45 ` Paul E. McKenney
2014-06-13 23:35 ` Dave Hansen
2014-06-14 2:03 ` Paul E. McKenney
2014-06-17 23:10 ` Dave Hansen
2014-06-18 0:00 ` Josh Triplett
2014-06-18 0:15 ` Andi Kleen
2014-06-18 1:04 ` Paul E. McKenney
2014-06-18 2:27 ` Andi Kleen
2014-06-18 4:47 ` Paul E. McKenney
2014-06-18 12:40 ` Andi Kleen
2014-06-18 12:56 ` Paul E. McKenney
2014-06-18 14:29 ` Christoph Lameter
2014-06-18 0:18 ` Paul E. McKenney
2014-06-18 6:33 ` Dave Hansen
2014-06-18 12:58 ` Paul E. McKenney
2014-06-18 17:36 ` Dave Hansen
2014-06-18 20:30 ` Paul E. McKenney
2014-06-18 23:51 ` Paul E. McKenney
2014-06-19 1:42 ` Andi Kleen
2014-06-19 2:13 ` Paul E. McKenney [this message]
2014-06-19 2:29 ` Paul E. McKenney
2014-06-19 2:50 ` Mike Galbraith
2014-06-19 4:19 ` Paul E. McKenney
2014-06-19 3:38 ` Andi Kleen
2014-06-19 4:19 ` Paul E. McKenney
2014-06-19 5:24 ` Mike Galbraith
2014-06-19 18:14 ` Paul E. McKenney
2014-06-19 4:52 ` Eric Dumazet
2014-06-19 5:23 ` Paul E. McKenney
2014-06-19 14:42 ` Christoph Lameter
2014-06-19 18:09 ` Paul E. McKenney
2014-06-19 20:31 ` Christoph Lameter
2014-06-19 20:42 ` Paul E. McKenney
2014-06-19 20:50 ` Andi Kleen
2014-06-19 21:03 ` Paul E. McKenney
2014-06-19 21:13 ` Christoph Lameter
2014-06-19 21:16 ` Christoph Lameter
2014-06-19 21:32 ` josh
2014-06-19 23:07 ` Paul E. McKenney
2014-06-20 15:20 ` Christoph Lameter
2014-06-20 15:38 ` Paul E. McKenney
2014-06-20 16:07 ` Christoph Lameter
2014-06-20 16:30 ` Paul E. McKenney
2014-06-20 17:39 ` Dave Hansen
2014-06-20 18:15 ` Paul E. McKenney
2014-06-18 21:48 ` Paul E. McKenney
2014-06-18 22:03 ` Dave Hansen
2014-06-18 22:52 ` Paul E. McKenney
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