220 41277 <992426dc-b7a7-2ffa-2937-8f362593c8e8@gmail.com> article Path: news.gmane.org!.POSTED!not-for-mail From: Robin Rowe Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Multi-processing SharedMemory, Semaphore and RingBuffer classes Date: Sat, 22 Dec 2018 00:19:28 -0800 Lines: 78 Approved: news@gmane.org Message-ID: <992426dc-b7a7-2ffa-2937-8f362593c8e8@gmail.com> References: <84ce0721-ed7b-85cf-5434-1b8eb153ddab@gmail.com> <0ba51187-1ea5-4e75-978f-802f2d52cc59@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed X-Trace: blaine.gmane.org 1545466647 24843 195.159.176.226 (22 Dec 2018 08:17:27 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 22 Dec 2018 08:17:27 +0000 (UTC) User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.3 To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCUOVZFOBEIJHZ7X4ACRUBERQGMSG@isocpp.org Sat Dec 22 09:17:23 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pf1-f199.google.com ([209.85.210.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1gacTK-0006Hf-Ox for gclcip-std-proposals@m.gmane.org; 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[23.242.20.216]) by smtp.googlemail.com with ESMTPSA id 85sm37623342pfw.17.2018.12.22.00.19.29 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 22 Dec 2018 00:19:29 -0800 (PST) In-Reply-To: <0ba51187-1ea5-4e75-978f-802f2d52cc59@isocpp.org> Content-Language: en-US X-Original-Sender: robinsrowe@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=Sn79q8B9; spf=pass (google.com: domain of robinsrowe@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=robinsrowe@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:41277 Archived-At: Arthur, Thanks for catching me up on the history of previous ring queue attempts and code links. Interesting. Very helpful! Is there anyone who can also share what's come before for MP shared memory and semaphores? > Just so you have the right frame for however this thread develops. :) No expectations. I only seek to be useful. > Guy Davidson is still somewhat pursuing P0059 ring-buffer-related > work, but I'm not. Guy, if you're available here, can you share your thoughts? > Ring-buffers are like Concepts or Modules: everyone wants "a standard > ring-buffer type," but everyone thinks it means something slightly > different, such that nobody would actually be happy with the finished > product. Should it be thread-safe or thread-unsafe? Common practice suggests nobody sees a benefit to embedding locks in containers generally. A container should be thread-unsafe or lockfree, have external locks or not need locks. Because lockfree container performance is so poor generally, slower than thread-unsafe containers with external locks, let's set lockfree aside until we can show it works better. That leaves just one choice: thread-unsafe. > Should it own or not own its buffer? Because my ring buffer is in MP shared memory, it better own its data. > Should it be resizeable (and thus heap-allocated and > allocator-aware) or statically sized in-place? The typical use-case for a ring queue is for a communications buffer between threads or processes. We won't want that to be resizable or to try heap allocations during a real-time service request. Moreover, if for some reason we do decide we want a container like that, we already have the resizable and heap-based std::queue. > Your library chooses "thread-unsafe, owning, in-place." Yes, no other approach seems sensible for MP. With our use-case a comms buffer, that must work in a multi-processing or multi-threaded environment. To ensure not only the buffer but the apparatus of the container are in shared memory, "owning and in-place" seem the only way to go. Embracing the constraints of MP seems to force other slightly different solutions to fall away. > You should consider posting on codereview.stackexchange.com to get > specific library feedback. Thanks, implementation is still fresh. While I deeply appreciate your feedback, I won't take the bandwidth of this list for code review. Will follow up with you off-list. The feedback I'm seeking now is opinions of whether this is the right track toward a standard. Can this design overcome all the objections to previous efforts to standardize a ring queue and MP shared memory? https://github.com/robinrowe/multiprocessing Thanks! Robin -- Robin Rowe 323-535-0952 mobile Beverly Hills, California -- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/992426dc-b7a7-2ffa-2937-8f362593c8e8%40gmail.com. .