вівторок 21 березень 2006 17:48, Matthew Dillon Ви написали: > Reading via mmap() is very well optimized.
Actually, I can not agree here -- quite the opposite seems true. When running locally (no NFS involved) my compressor with the `-1' flag (fast, least effective compression), the program easily compresses faster, than it can read. The Opteron CPU is about 50% idle, *and so is the disk* producing only 15Mb/s. I guess, despite the noise I raised on this subject a year ago, reading via mmap continues to ignore the MADV_SEQUENTIONAL and has no other adaptability. Unlike read, which uses buffering, mmap-reading still does not pre-fault the file's pieces in efficiently :-( Although the program was written to compress files, that are _likely_ still in memory, when used with regular files, it exposes the lack of mmap optimization. This should be even more obvious, if you time searching for a string in a large file using grep vs. 'grep --mmap'. Yours, -mi http://aldan.algebra.com/~mi/mzip.c _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[EMAIL PROTECTED]"