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SubjectRe: [RFC][PATCH] srcu: Implement call_srcu()
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



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