From: Avi Kivity <avi@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@us.ibm.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 15:47:18 +0200 [thread overview]
Message-ID: <4F27F0E6.1040309@redhat.com> (raw)
In-Reply-To: <1328016724.2446.229.camel@twins>
On 01/31/2012 03:32 PM, Peter Zijlstra wrote:
> Subject: srcu: Implement call_srcu()
> From: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Date: Mon Jan 30 23:20:49 CET 2012
>
> Implement call_srcu() by using a state machine driven by
> call_rcu_sched() and timer callbacks.
>
> The state machine is a direct derivation of the existing
> synchronize_srcu() code and replaces synchronize_sched() calls with a
> call_rcu_sched() callback and the schedule_timeout() calls with simple
> timer callbacks.
>
> It then re-implements synchronize_srcu() using a completion where we
> send the complete through call_srcu().
>
> It completely wrecks synchronize_srcu_expedited() which is only used
> by KVM. 3 of the 5
2 of the 5
> use cases look like they really want to use
> call_srcu() instead, the remaining 2 I don't know but hope they can,
> which would let us remove it.
They really need to return quickly to userspace, and they really need to
perform some operation between rcu_assign_pointer() and returning, so no.
>
> Compile tested only!! :-)
>
How much did synchronize_srcu_expedited() regress? Presumably your
compiler didn't tell you that.
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.
--
error compiling committee.c: too many arguments to function
next parent reply other threads:[~2012-01-31 13:47 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1328016724.2446.229.camel@twins>
2012-01-31 13:47 ` Avi Kivity [this message]
2012-01-31 13:50 ` [RFC][PATCH] srcu: Implement call_srcu() Peter Zijlstra
2012-01-31 22:24 ` Paul E. McKenney
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
2012-02-08 15:43 ` [RFC] need to improve slot creation/destruction? -- " Takuya Yoshikawa
2012-02-08 18:45 ` Marcelo Tosatti
2012-02-09 13:48 ` Takuya Yoshikawa
2012-02-09 14:25 ` Avi Kivity
2012-02-10 17:16 ` Marcelo Tosatti
2012-02-14 9:52 ` Avi Kivity
2012-02-09 14:23 ` Avi Kivity
2012-02-09 14:24 ` Avi Kivity
2012-02-10 13:08 ` Takuya Yoshikawa
2012-02-10 17:17 ` Marcelo Tosatti
2012-02-10 13:25 ` Takuya Yoshikawa
2012-02-14 9:52 ` Avi Kivity
2012-02-01 14:07 ` Paul E. McKenney
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