linux-kernel - Re: [PATCH] cpuacct: add a branch prediction

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: <20090226174303.9234fd60.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 26 Feb 2009 17:43:03 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	balbir@...ux.vnet.ibm.com
Cc:	Li Zefan <lizf@...fujitsu.com>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Menage <menage@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpuacct: add a branch prediction

On Thu, 26 Feb 2009 14:07:02 +0530
Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:

> * Li Zefan <lizf@...fujitsu.com> [2009-02-26 15:40:15]:
> 
> > cpuacct_charge() is in fast-path, and checking of !cpuacct_susys.active
> > always returns false after cpuacct has been initialized at system boot.
> > 
> > Signed-off-by: Li Zefan <lizf@...fujitsu.com>
> > ---
> >  kernel/sched.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/kernel/sched.c b/kernel/sched.c
> > index 410eec4..fd2f7fc 100644
> > --- a/kernel/sched.c
> > +++ b/kernel/sched.c
> > @@ -9589,7 +9589,7 @@ static void cpuacct_charge(struct task_struct *tsk, u64 cputime)
> >  	struct cpuacct *ca;
> >  	int cpu;
> > 
> > -	if (!cpuacct_subsys.active)
> > +	if (unlikely(!cpuacct_subsys.active))
> 
> What happens if most distros make cpuacct_subsys active? Can we decide
> on unlikely depending on how the system is configured?
>
"active" just guarantees task_ca(tsk) is not NULL and subsystem is initialized.

Thanks,
-Kame

--
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/