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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 18 Jun 2014 21:19:51 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
Cc:	Andi Kleen <ak@...ux.intel.com>,
	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

On Thu, Jun 19, 2014 at 04:50:19AM +0200, Mike Galbraith wrote:
> On Wed, 2014-06-18 at 19:13 -0700, Paul E. McKenney wrote: 
> > 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.
> 
> Not everybody, SUSE doesn't even have it enabled in factory.

OK, apologies for the over-generalization.

But you would think that I would have learned this lesson with
CONFIG_RCU_FAST_NO_HZ, wouldn't you?  :-/

							Thanx, Paul

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/