in reply to Re^7: Calling a sub from a variable ?
in thread Calling a sub from a variable ?

I'll confess i don't know much about optree.
Does that means that each time you use a module it's loaded from disk ? Does compile always issue a disk IO ?

It seems to me that the VMM filesystem cache system will ensure that once accessed from disk the data stays in memory, thus discarding disk IO .

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Re^9: Calling a sub from a variable ?
by dragonchild (Archbishop) on Mar 22, 2005 at 15:23 UTC
    That depends on a bazillion factors, a few of which are:
    • your actual harddrive - some do onboard caching, some don't. Some have adapative search strategies, most don't.
    • where it's located - is it in the case or on the network somewhere?
    • how you're connected to it - megabit? dual-gigabit SAN? Serial? SCSI?
    • what OS you're using - MS vs. Linux vs. Solaris vs. VMS vs. ...
    • what filesystem you're using - ext3 vs. reiser3 vs. reiser4 vs. WinFS vs. ...
    • Any number of options your sysadmin(s) might have set
    • The rest of the load on the box / SAN / etc ...
    • Any caching done by other applications - Oracle, for instance, has some aggressive caching
    • How much RAM you have - it doesn't help your I/O speed if your cache is in a page which is on disk
    In other words, the benchmark can vary even by time of day or day of the week or even day of the year. (If you have a bunch of quarterly reports that are run, that can affect your database load which affects your OS caching performance which affect your ... you get the picture.)

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[reply]
      I agree with that.

      This server is a Solaris 5.8 server with a hudge free list (3 638 832 K right now and it stays over 1 Gb at program runtime) .

      I believe the FS cache has not been tuned although i know more of this with AIX. Anyhow there is plenty of free pages to cache the data and thus descarding IO in that special case. As you say, it could have been different .

[reply]

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