From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH v3 2/5] util: introduce threaded workqueue Date: Tue, 27 Nov 2018 16:31:31 +0800 Message-ID: References: <20181122072028.22819-1-xiaoguangrong@tencent.com> <20181122072028.22819-3-xiaoguangrong@tencent.com> <20181124001734.GF17229@flamenco> <122f7c3b-ebaf-a2c0-3181-cce82d857058@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: kvm@vger.kernel.org, mst@redhat.com, mtosatti@redhat.com, Xiao Guangrong , dgilbert@redhat.com, peterx@redhat.com, qemu-devel@nongnu.org, quintela@redhat.com, wei.w.wang@intel.com, jiang.biao2@zte.com.cn To: Paolo Bonzini , "Emilio G. Cota" Return-path: In-Reply-To: Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel2=m.gmane.org@nongnu.org Sender: "Qemu-devel" List-Id: kvm.vger.kernel.org On 11/26/18 6:28 PM, Paolo Bonzini wrote: > 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). That's good to me. will try it. ;) From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59679) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gRYmW-0001Yi-VV for qemu-devel@nongnu.org; Tue, 27 Nov 2018 03:31:46 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gRYmR-0008EX-Vo for qemu-devel@nongnu.org; Tue, 27 Nov 2018 03:31:44 -0500 Received: from mail-pl1-x641.google.com ([2607:f8b0:4864:20::641]:35816) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1gRYmR-0008DV-N8 for qemu-devel@nongnu.org; Tue, 27 Nov 2018 03:31:39 -0500 Received: by mail-pl1-x641.google.com with SMTP id p8so4967030plo.2 for ; Tue, 27 Nov 2018 00:31:39 -0800 (PST) References: <20181122072028.22819-1-xiaoguangrong@tencent.com> <20181122072028.22819-3-xiaoguangrong@tencent.com> <20181124001734.GF17229@flamenco> <122f7c3b-ebaf-a2c0-3181-cce82d857058@gmail.com> From: Xiao Guangrong Message-ID: Date: Tue, 27 Nov 2018 16:31:31 +0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH v3 2/5] util: introduce threaded workqueue List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini , "Emilio G. Cota" Cc: mst@redhat.com, mtosatti@redhat.com, qemu-devel@nongnu.org, kvm@vger.kernel.org, dgilbert@redhat.com, peterx@redhat.com, wei.w.wang@intel.com, jiang.biao2@zte.com.cn, eblake@redhat.com, quintela@redhat.com, Xiao Guangrong On 11/26/18 6:28 PM, Paolo Bonzini wrote: > 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). That's good to me. will try it. ;)