From: Avi Kivity <avi@redhat.com>
To: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Cc: Peter Zijlstra <peterz@infradead.org>,
paulmck@linux.vnet.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: Wed, 01 Feb 2012 13:01:38 +0200 [thread overview]
Message-ID: <4F291B92.8070402@redhat.com> (raw)
In-Reply-To: <4F291B56.30600@oss.ntt.co.jp>
On 02/01/2012 01:00 PM, Takuya Yoshikawa wrote:
>
>> rcu_assign_pointer), and use atomic operations to copy and clear:
>>
>> word = bitmap[i]
>> put_user(word)
>> atomic_and(&bitmap[i], ~word)
>>
>>
>
> This kind of this was really slow IIRC.
>
>
> How about just doing:
>
> take a spin_lock
> copy the entire (or some portions of) bitmap locally
> clear the bitmap
> unlock
>
That means that vcpus dirtying memory also have to take that lock, and
spin while the bitmap is being copied. So kvm_vm_ioctl_get_dirty_log()
will become faster, at the expense of vcpus, which I think is a bad
tradeoff.
> write protect the dirty pages based on the copied dirty data
>
> copy_to_user
>
>
>
> I can show you some performance numbers, this weekend, if you like.
That'll be great, numbers are better than speculation.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2012-02-01 11:01 UTC|newest]
Thread overview: 35+ 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
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 [this message]
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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