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/
