Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Delivered-To: mailing list cygwin@cygwin.com Date: Wed, 27 Nov 2002 22:39:05 +0100 From: thomas Reply-To: thomas X-Priority: 3 (Normal) Message-ID: <14936170000.20021127223905@huno.net> To: cygwin@cygwin.com Subject: Re: pipe performance problem In-Reply-To: <10824453046.20021123003030@huno.net> References: <20021122210856.GA10679@redhat.com> <777770015.20021122040845@huno.net> <007301c291ff$eb9ce050$78d96f83@pomello> <21545718.20021122114035@huno.net> <12415481703.20021122220059@huno.net> <20021122210856.GA10679@redhat.com> <5.1.0.14.2.20021122143402.00fdc148@pop3.cris.com> <10824453046.20021123003030@huno.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Hi List, I'm back with more information, I've narrowed down the problem further with another strace session. I've run: cat test.iso | strace -o dd1.log nice --1 dd of=/dev/null cat test.iso | strace -o dd0.log nice --0 dd of=/dev/null nice --1 needs much longer, like already shown in another thread here. But the strace logs seem to be absolutely the same, in fact --1 is faster like it should be. You can clearly see that it needs a few microseconds less than --0 for each operation, but then i found this in dd1.log: 24 40524 [main] dd 2384 writev: 512 = write (1, 0x240FD3C, 1), errno 0 25 40549 [main] dd 2384 readv: readv (0, 0x240FD9C, 1) blocking, sigcatchers 4 10588 51137 [main] dd 2384 peek_pipe: /dev/piper, ready for read 34 51171 [main] dd 2384 fhandler_base::ready_for_read: read_ready 1, avail 1 29 51200 [main] dd 2384 fhandler_base::read: returning 512 chars, binary mode ... 10147 78483 [main] dd 2384 peek_pipe: /dev/piper, ready for read ... 10163 105142 [main] dd 2384 peek_pipe: /dev/piper, ready for read 10 ms delay, and there's many of them. Exactly every 612 lines or every 34816 bytes (34kb). Which is about 210 seconds delay on a 700MB file. It doesn't happen with --0 at all. So i looked what peek_pipe in select.cc does but i didn't find anything suspicious (or is readv responsible here?). Now before i continue to dig through more code i'd greatly appreciate if someone can confirm that this is not expected behaviour. thomas -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Bug reporting: http://cygwin.com/bugs.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/