I realized I forgot to follow-up on this thread. Just to be clear, I have confirmed that I am seeing what to me is undesirable behavior even with the ARC being 1500 MB in size on an almost idle system (< 0.5 mb/sec read load, almost 0 write load). Observe these recursive searches through /usr/src/sys:
% time ack arcstats 2>/dev/null 1>/dev/null ack arcstats 2.74s user 1.19s system 20% cpu 19.143 total % time ack arcstats 2>/dev/null 1>/dev/null ack arcstats 2> /dev/null > /dev/null 2.45s user 0.51s system 99% cpu 2.986 total % time ack arcstats 2>/dev/null 1>/dev/null ack arcstats 2> /dev/null > /dev/null 2.41s user 0.62s system 53% cpu 5.667 total % time ack arcstats 2>/dev/null 1>/dev/null ack arcstats 2> /dev/null > /dev/null 2.37s user 0.68s system 50% cpu 6.025 total % time ack arcstats 2>/dev/null 1>/dev/null ack arcstats 2> /dev/null > /dev/null 2.45s user 0.61s system 45% cpu 6.694 total % time ack arcstats 2>/dev/null 1>/dev/null ack arcstats 2> /dev/null > /dev/null 2.45s user 0.59s system 53% cpu 5.651 total % time ack arcstats 2>/dev/null 1>/dev/null ack arcstats 2> /dev/null > /dev/null 2.32s user 0.72s system 46% cpu 6.503 total % time ack arcstats 2>/dev/null 1>/dev/null ack arcstats 2> /dev/null > /dev/null 2.41s user 0.66s system 44% cpu 6.843 total % time ack arcstats 2>/dev/null 1>/dev/null ack arcstats 2> /dev/null > /dev/null 2.37s user 0.67s system 49% cpu 6.119 total The first was entirely cold. For some reason the second was close to CPU-bound, while the remainder were significantly disk-bound even if not to the extent of the initial run. I correlated with 'iostat -x 1' to confirm that I am in fact generating I/O (but no, I do not have dtrace output). Anyways, presumably the answer to my original question is no and the above isn't really very interesting other than to show that under some circumstances you can see behavior that is decidedly non-optimal for interactive desktop use of certain kinds. Whether this is ARC in general or something FreeBSD specific, I don't know. But it does, at this point, not have to do with ARC sizing since the ARC is sensibly large. (I realize I should investigate properly and report back, but I'm not likely to have time to dig into this now.) -- / Peter Schuller _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
