Re: [TEKNIK] disc cache, ramdisk, mm.

[Mogens Kjaer <sslug@sslug>]

Troels Arvin wrote:
...
> Bliver caching-effekten annulleret hos dig, hvis du afmonterer og 
> derefter genmonterer?

Det er min rodpartition, såh...

Hvis jeg kører en "hdparm -t -T /dev/sda" ind imellem
de to dd'er er der ingen cache effekt i den anden dd, selv om
hdparm jamrer:

# dd if=/dev/sda of=/dev/null bs=8192 count=100000
100000+0 records in
100000+0 records out
819200000 bytes (819 MB) copied, 3.25 seconds, 252 MB/s
# hdparm -t -T /dev/sda

/dev/sda:
 Timing cached reads:   12392 MB in  2.00 seconds = 6203.22 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate 
ioctl for device
 Timing buffered disk reads:  628 MB in  3.01 seconds = 208.97 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate 
ioctl for device
# dd if=/dev/sda of=/dev/null bs=8192 count=100000
100000+0 records in
100000+0 records out
819200000 bytes (819 MB) copied, 3.52136 seconds, 233 MB/s

Det ser ud til at hdparm kan bruges til at tømme cachen.

Mogens

--
Mogens Kjaer, Carlsberg A/S, Computer Department
Gamle Carlsberg Vej 10, DK-2500 Valby, Denmark
Phone: +45 33 27 53 25, Fax: +45 33 27 47 08
Email: sslug@sslug Homepage: http://www.crc.dk