From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from conssluserg-06.nifty.com (conssluserg-06.nifty.com [210.131.2.91]) by sourceware.org (Postfix) with ESMTPS id ACF2A3858435 for ; Sat, 28 Aug 2021 15:43:59 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org ACF2A3858435 Received: from Express5800-S70 (z221123.dynamic.ppp.asahi-net.or.jp [110.4.221.123]) (authenticated) by conssluserg-06.nifty.com with ESMTP id 17SFhgYo030934 for ; Sun, 29 Aug 2021 00:43:42 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-06.nifty.com 17SFhgYo030934 X-Nifty-SrcIP: [110.4.221.123] Date: Sun, 29 Aug 2021 00:43:46 +0900 From: Takashi Yano To: cygwin@cygwin.com Subject: Re: cygrunsrv + sshd + rsync = 20 times too slow -- throttled? Message-Id: <20210829004346.c2f80469abc3a07fd4b2918d@nifty.ne.jp> In-Reply-To: References: <20210825201845.07b6400b79dc5558a7761efe@nifty.ne.jp> <20210826062934.54f2f2216021c095bb7ba13b@nifty.ne.jp> <3b560051-ab27-f392-ca4b-d1fd9b5733b0@cornell.edu> <20210827202440.47706fc2fc07c5e9a1bc0047@nifty.ne.jp> <4f2cb5f3-ce9c-c617-f65f-841a5eca096e@cornell.edu> <20210828022111.91ef5b4ff24f6da9fadb489e@nifty.ne.jp> <20210828184102.f2206a8a9e5fe5cf24bf5e45@nifty.ne.jp> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.30; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: cygwin@cygwin.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: General Cygwin discussions and problem reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 28 Aug 2021 15:44:11 -0000 On Sat, 28 Aug 2021 13:58:08 +0200 Corinna Vinschen wrote: > On Aug 28 18:41, Takashi Yano via Cygwin wrote: > > On Sat, 28 Aug 2021 10:43:27 +0200 > > Corinna Vinschen wrote: > > > On Aug 28 02:21, Takashi Yano via Cygwin wrote: > > > > On Fri, 27 Aug 2021 12:00:50 -0400 > > > > Ken Brown wrote: > > > > > Two years ago I thought I needed nt_create to avoid problems when calling > > > > > set_pipe_non_blocking. Are you saying that's not an issue? Is > > > > > set_pipe_non_blocking unnecessary? Is that the point of your modification to > > > > > raw_read? > > > > > > > > Yes. Instead of making windows read function itself non-blocking, > > > > it is possible to check if the pipe can be read before read using > > > > PeekNamedPipe(). If the pipe cannot be read right now, EAGAIN is > > > > returned. > > > > > > The problem is this: > > > > > > if (PeekNamedPipe()) > > > ReadFile(blocking); > > > > > > is not atomic. I. e., if PeekNamedPipe succeeds, nothing keeps another > > > thread from draining the pipe between the PeekNamedPipe and the ReadFile > > > call. And as soon as ReadFile runs, it hangs indefinitely and we can't > > > stop it via a signal. > > > > Hmm, you are right. Mutex guard seems to be necessary like pty code > > if we go this way. > > > > > Is a blocking ReadFile actually faster than a non-blocking read? Or > > > does it mainly depend on BYTE vs. MESSAGE mode? > > > > Actually, I don't think so. Perhaps it is not essential problem of > > overlapped I/O but something is wrong with current pipe code. > > > > > What if the pipe is created non-blocking and stays non-blocking all the > > > time and uses BYTE mode all the time? Just as sockets, it would always > > > only emulate blocking mode. Wouldn't that drop code size a lot and fix > > > most problems? > > > > If 'non-blocking' means overlapped I/O, only the problem will be: > > https://cygwin.com/pipermail/cygwin/2021-March/247987.html > > Sorry if that wasn't clear, but I was not talking about overlapped I/O, > which we should get rid off, but of real non-blocking mode, which > Windows pipes are fortunately capable of. Do you mean, PIPE_NOWAIT flag? If this flags is specified in the read pipe, non-cygwin apps cannot read the pipe correctly. -- Takashi Yano