From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ffbox0-bg.mplayerhq.hu (ffbox0-bg.ffmpeg.org [79.124.17.100]) by master.gitmailbox.com (Postfix) with ESMTP id 1CD18428E1 for ; Tue, 5 Apr 2022 19:46:13 +0000 (UTC) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id C8BCF68B1FE; Tue, 5 Apr 2022 22:46:11 +0300 (EEST) Received: from mail0.khirnov.net (red.khirnov.net [176.97.15.12]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id DEBDF68B186 for ; Tue, 5 Apr 2022 22:46:05 +0300 (EEST) Received: from localhost (localhost [IPv6:::1]) by mail0.khirnov.net (Postfix) with ESMTP id 4EFBC240179 for ; Tue, 5 Apr 2022 21:46:05 +0200 (CEST) Received: from mail0.khirnov.net ([IPv6:::1]) by localhost (mail0.khirnov.net [IPv6:::1]) (amavisd-new, port 10024) with ESMTP id mLHxknFfzpxm for ; Tue, 5 Apr 2022 21:46:04 +0200 (CEST) Received: from lain.red.khirnov.net (lain.red.khirnov.net [IPv6:2001:67c:1138:4306::3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "lain.red.khirnov.net", Issuer "smtp.khirnov.net SMTP CA" (verified OK)) by mail0.khirnov.net (Postfix) with ESMTPS id 95F3F2400F5 for ; Tue, 5 Apr 2022 21:46:04 +0200 (CEST) Received: by lain.red.khirnov.net (Postfix, from userid 1000) id AEEF21601AD; Tue, 5 Apr 2022 21:46:04 +0200 (CEST) From: Anton Khirnov To: FFmpeg development discussions and patches In-Reply-To: <20220405191542.GV2829255@pb2> References: <20220404113037.13070-1-anton@khirnov.net> <20220405191542.GV2829255@pb2> Mail-Followup-To: FFmpeg development discussions and patches Date: Tue, 05 Apr 2022 21:46:04 +0200 Message-ID: <164918796468.24258.6158464741625303482@lain.red.khirnov.net> User-Agent: alot/0.8.1 MIME-Version: 1.0 Subject: Re: [FFmpeg-devel] [RFC] Switching ffmpeg.c to a threaded architecture X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Archived-At: List-Archive: List-Post: Quoting Michael Niedermayer (2022-04-05 21:15:42) > On Mon, Apr 04, 2022 at 01:29:48PM +0200, Anton Khirnov wrote: > > Hi, > > this WIP patchset is the first major part of my ongoing work to change > > ffmpeg.c architecture such that every > > - demuxer > > - decoder > > - filtergraph > > - encoder > > - muxer > > lives in its own thread. The advantages of doing this, beyond increased > > throughput, would be enforced separation between these components, > > making the code more local and easier to reason about. > > > > This set implements threading for muxers. My tentative plan is to > > continue with encoders and then filters. The patches still need some > > polishing, especially the last one. Two FATE tests do not yet pass, this > > will be fixed in later iterations. > > > > Meanwhile, comments on the overall approach are especially welcome. > > I agree that cleanup/modularization to make the code easier to > understand is a good idea! > Didnt really look at the patchset yet. > I assume these changes have no real disadvantage ? Playing the devil's advocate, I can think of the following: 1) ffmpeg.c will hard-depend on threads 2) execution flow will become non-deterministic 3) overall resource usage will likely go up due to inter-thread synchronization and overhead related to new objects 4) large-scale code changes always carry a higher risk of regressions re 1): should not be a problem for any serious system re 2): I spent a lot of effort to ensure the _output_ remains deterministic (it actually becomes more predictable for some cases) re 3): I expect the impact to be small and negligible, respectively, but would have to be measured once the conversion is complete re 4): the only way to avoid this completely would be to stop development Overall, I believe the advantages far outweigh the potential negatives. -- Anton Khirnov _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".