Re: PATCH: rewritten bdflush

Pavel Machek (pavel@atrey.karlin.mff.cuni.cz)
Fri, 14 May 1999 12:04:40 +0200


Hi!

> > > There is one notable side effect: you don't have to run the user space
> > > update anymore, bdflush wakes up every so often all by itself. I
> >
> > How about notebook users who have configured update to stop
> > writing out buffers and spin down disks after some idle time?
>
> I think we might want to change the kernel's behaviour
> to include the following things:
> - don't flush if:
> - there are less than X dirty buffers &&
> - we haven't recently read from the disk
> - flush if:
> - there are more than X dirty buffers ||
> - we issued a read from the disk more than
> Y and less than Z seconds ago ||
> - the dirty buffer is FAR too old
> (say, an hour or so)

This is policy. Policy does not belong in kernel. (I, for example, do
not like hour limit - it is way too low. My atimes do not need to be
written; system can run 2 hours on backup batery and will suspend to
disk after that. Only chance for crash is kernel bug. And there are no
bugs in stable kernel, are they?

[but I believe this is much better than current status]

Pavel

PS: So there's at least one system, which just can not crash. Why do
you want to sync 1 hour old buffers to disk on it? Why do you want to
sync 1 year old buffers to disk? You don't want.

-- 
The best software in life is free (not shareware)!		Pavel
GCM d? s-: !g p?:+ au- a--@ w+ v- C++@ UL+++ L++ N++ E++ W--- M- Y- R+

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