On Fri, 2006-Mar-24 15:18:00 -0500, Mikhail Teterin wrote: >On the machine, where both mzip and the disk run at only 50%, the disk is a >plain SATA drive (mzip's state goes from "RUN" to "vnread" and back). ... > 18 users Load 0.46 0.53 0.60 24 ??? 15:15 > >Mem:KB REAL VIRTUAL VN PAGER SWAP PAGER > Tot Share Tot Share Free in out in out >Act 1833864 5880 27758552 45268 92216 count 240 >All 1881188 5992 1432466k 52864 pages 3413 > Interrupts >Proc:r p d s w Csw Trp Sys Int Sof Flt cow 2252 total > 1 2101 1605 2025 197 422 2 2018 251432 wire irq1: > atkb > 506156 act irq6: > fdc0 > 3.0%Sys 0.0%Intr 45.2%User 0.0%Nice 51.9%Idl 1038216 inact irq15: > ata >| | | | | | | | | | 89252 cache irq17: >fwo >=>>>>>>>>>>>>>>>>>>>>>>> 2964 free irq20: >nve > daefr irq21: > ohc >Namei Name-cache Dir-cache prcfr 241 irq22: >ehc > Calls hits % hits % 951 react 11 irq25: > em0 > pdwak irq29: > amr > 618 zfod pdpgs 2000 cpu0: > time >Disks ad4 amrd0 ofod intrn >KB/t 56.79 0.00 %slo-z 200816 buf >tps 241 0 5143 tfree 8 dirtybuf >MB/s 13.38 0.00 100000 desiredvnodes >% busy 47 0 34717 numvnodes > 24991 freevnodes
OK. I _can_ see something like this when I try to compress a big file using either your program or gzip. In my case, both the disk % busy and system idle vary widely but there's typicaly 50-60% disk utilisation and 30-40% CPU idle. However, systat is reporting 23-25MB/sec (whereas dd peaks at ~30MB/sec) so the time to gzip the datafile isn't that much different to the time to just read it. My guess is that the read-ahead algorithms are working but aren't doing enough re-ahead to cope with "read a bit, do some cpu-intensive processing and repeat" at 25MB/sec so you're winding up with a degree of serialisation where the I/O and compressing aren't overlapped. I'm not sure how tunable the read-ahead is. -- Peter Jeremy _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[EMAIL PROTECTED]"
