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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <20140619180916.GE4904@linux.vnet.ibm.com>
Date:	Thu, 19 Jun 2014 11:09:16 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Christoph Lameter <cl@...two.org>
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>
Subject: Re: [bisected] pre-3.16 regression on open() scalability

On Thu, Jun 19, 2014 at 09:42:18AM -0500, Christoph Lameter wrote:
> On Wed, 18 Jun 2014, 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.
> >
> > 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.
> 
> Again I am fully on Andi's side here. Please remove these frequent calls
> to cond_resched. If one wants a fully preemptable kernel then please use
> CONFIG_PREEMPT.

That is a separate issue, but unnecessary calls to cond_resched()
should of course be removed -- no argument there.

							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/