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Re: [Qemu-devel] [PATCH 5/9] exec: protect mru_block with RCU
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 5/9] exec: protect mru_block with RCU |
Date: |
Thu, 05 Feb 2015 09:37:16 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 |
On 05/02/2015 07:23, Fam Zheng wrote:
>> > @@ -1381,14 +1397,16 @@ static ram_addr_t ram_block_add(RAMBlock
>> > *new_block, Error **errp)
>> > QTAILQ_INSERT_TAIL(&ram_list.blocks, new_block, next);
>> > }
>> > ram_list.mru_block = NULL;
>> > + atomic_rcu_set(&ram_list.version, ram_list.version + 1);
>> >
>> > - ram_list.version++;
> Why is this not atomic_inc
Because writes are protected by the ramlist lock. atomic_inc is more
expensive.
> (or why is atomic_rcu_set necessary here)?
I probably should move it to patch 9; it is needed to update the list
before ram_list.version.
If you prefer I can change it to
smp_wmb();
atomic_set(&ram_list.version, ram_list.version + 1);
?
Paolo
[Qemu-devel] [PATCH 6/9] cosmetic changes preparing for the following patches, Paolo Bonzini, 2015/02/03
[Qemu-devel] [PATCH 8/9] exec: convert ram_list to QLIST, Paolo Bonzini, 2015/02/03
[Qemu-devel] [PATCH 2/9] exec: make iotlb RCU-friendly, Paolo Bonzini, 2015/02/03