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Re: [Qemu-devel] [PATCH v3 2/5] util: introduce threaded workqueue
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v3 2/5] util: introduce threaded workqueue |
Date: |
Mon, 26 Nov 2018 11:28:28 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 |
On 26/11/18 09:18, Xiao Guangrong wrote:
>>
>>> +static uint64_t get_free_request_bitmap(Threads *threads,
>>> ThreadLocal *thread)
>>> +{
>>> + uint64_t request_fill_bitmap, request_done_bitmap, result_bitmap;
>>> +
>>> + request_fill_bitmap =
>>> atomic_rcu_read(&thread->request_fill_bitmap);
>>> + request_done_bitmap =
>>> atomic_rcu_read(&thread->request_done_bitmap);
>>> + bitmap_xor(&result_bitmap, &request_fill_bitmap,
>>> &request_done_bitmap,
>>> + threads->thread_requests_nr);
>>
>> This is not wrong, but it's a big ugly. Instead, I would:
>>
>> - Introduce bitmap_xor_atomic in a previous patch
>> - Use bitmap_xor_atomic here, getting rid of the rcu reads
>
> Hmm, however, we do not need atomic xor operation here... that should be
> slower than
> just two READ_ONCE calls.
Yeah, I'd just go with Guangrong's version. Alternatively, add
find_{first,next}_{same,different}_bit functions (whatever subset of the
4 you need).
Paolo
Re: [Qemu-devel] [PATCH v3 2/5] util: introduce threaded workqueue, Emilio G. Cota, 2018/11/23
Re: [Qemu-devel] [PATCH v3 2/5] util: introduce threaded workqueue, Emilio G. Cota, 2018/11/23
Re: [Qemu-devel] [PATCH v3 2/5] util: introduce threaded workqueue, Christophe de Dinechin, 2018/11/27
[Qemu-devel] [PATCH v3 3/5] migration: use threaded workqueue for compression, guangrong . xiao, 2018/11/22