From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Avi Kivity <avi@redhat.com>, Oleg Nesterov <oleg@redhat.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Marcelo Tosatti <mtosatti@redhat.com>,
KVM list <kvm@vger.kernel.org>
Subject: Re: [RFC][PATCH] srcu: Implement call_srcu()
Date: Tue, 31 Jan 2012 14:24:47 -0800 [thread overview]
Message-ID: <20120131222447.GH2391@linux.vnet.ibm.com> (raw)
In-Reply-To: <1328017807.2446.230.camel@twins>
On Tue, Jan 31, 2012 at 02:50:07PM +0100, Peter Zijlstra wrote:
> On Tue, 2012-01-31 at 15:47 +0200, Avi Kivity wrote:
>
> > They really need to return quickly to userspace, and they really need to
> > perform some operation between rcu_assign_pointer() and returning, so no.
>
> Bugger :/
>
> > >
> > > Compile tested only!! :-)
> > >
> >
> > How much did synchronize_srcu_expedited() regress? Presumably your
> > compiler didn't tell you that.
>
> Nope, quite a lot I figure.
>
> > Can we get it back to speed by scheduling a work function on all cpus?
> > wouldn't that force a quiescent state and allow call_srcu() to fire?
> >
> > In kvm's use case synchronize_srcu_expedited() is usually called when no
> > thread is in a critical section, so we don't have to wait for anything
> > except the srcu machinery.
>
> OK, I'll try and come up with means of making it go fast again ;-)
I cannot resist suggesting a kthread to do the call_srcu(), which
would allow synchronize_srcu_expedited() to proceed with its current
brute-force speed.
Thanx, Paul
next prev parent reply other threads:[~2012-01-31 22:24 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-31 13:32 [RFC][PATCH] srcu: Implement call_srcu() Peter Zijlstra
2012-01-31 13:47 ` Avi Kivity
2012-01-31 13:50 ` Peter Zijlstra
2012-01-31 22:24 ` Paul E. McKenney [this message]
2012-02-01 10:22 ` Peter Zijlstra
2012-02-01 10:44 ` Avi Kivity
2012-02-01 10:49 ` Avi Kivity
2012-02-01 11:00 ` Takuya Yoshikawa
2012-02-01 11:01 ` Avi Kivity
2012-02-01 11:12 ` Takuya Yoshikawa
2012-02-01 13:24 ` Avi Kivity
2012-02-02 5:46 ` [test result] dirty logging without srcu update -- " Takuya Yoshikawa
2012-02-02 10:10 ` Avi Kivity
2012-02-02 10:21 ` Takuya Yoshikawa
2012-02-02 10:21 ` Avi Kivity
2012-02-02 10:40 ` Takuya Yoshikawa
2012-02-02 11:02 ` Avi Kivity
2012-02-02 14:44 ` Takuya Yoshikawa
2012-02-02 14:57 ` Avi Kivity
2012-02-01 13:43 ` Marcelo Tosatti
2012-02-01 15:42 ` Takuya Yoshikawa
2012-02-01 13:50 ` Marcelo Tosatti
2012-02-01 14:07 ` Paul E. McKenney
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