Russell King wrote:
>
> On Mon, Jun 17, 2002 at 12:33:18PM +0200, Martin Dalecki wrote:
> ...
> > > +int dirty_expire_centisecs = 30 * 100;
> > > +
> >
> > Blind guess - didn't the 100 wan't to be HZ?!
>
> The units are centiseconds (as the name suggests). 5 * 100 centiseconds = 5
> seconds, so the dirty writeback timeout is 5 seconds. Check the code a
> little further and you'll see HZ gets factored into them on use.
>
Yup. Sorry about the "_centisecs" thing. That's a bit anal, but
I tend to think that it's best to be really explicit about the
units, make it a bit easier to use. I don't know how many times
I've had to peer in fs/buffer.c to remember what those dang numbers do.
Possibly, "seconds" may be sufficiently high resolution for
these things. But I wasn't sure - maybe someone wants to
run the kupdate function five times per second? Dunno.
There are some departures from 2.4 tradition which are worth
mentioning here:
- There is no range checking on the settings. (But a divide-by
zero isn't possible, so I think that's OK)
- Unlike the 2.4 bdflush settings, these parameters are not
updated in a single hit. So if you modify them by a large
amount while the system is under heavy writeback load, perhaps
some whacky things will happen if you create an irrational
intermediate state. But that's quite unlikely.
- Unlike 2.4, the settings are scaled by HZ. So that bdflush
tuning tool whose name I forget will no longer make kupdate
run ten times too fast on Alphas.
-
-
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This archive was generated by hypermail 2b29 : Sun Jun 23 2002 - 22:00:14 EST