RE: Buffer and page cache

Stephen C. Tweedie (sct@redhat.com)
Mon, 8 Nov 1999 11:44:16 +0000 (GMT)


Hi,

On Sun, 7 Nov 1999 21:49:46 -0700, "braam"
<braam@carissimi.coda.cs.cmu.edu> said:

-> > What appears to be needed is the following - probably it's mostly
-> > lacking in my understanding, but I'd appreciate to be advised how to
-> > attack the following points:
->
-> > - a bit to keep shrink_mmap away from the page.
->
-> Yes, bumping the page count is the perfect way to do this.

> If we do that, how can the VM still exert pressure to get rid of dirty
> pages?

We were talking about pages with IO in progress IIRC. There is no need
to worry about VM pressure on those.

More concerning is the general issue of memory pressure on filesystems
which, due to complex mechanisms such as transaction write-ordering
requirements or defered allocation of disk blocks to data, cannot
arbitrarily flush individual pages back to disk on demand. For such
long-lived structures in memory, we do need a decent place for the VM to
exert pressure --- this is still being worked out for 2.3.

> Great I agree: a file system generic pointer would help a lot. Can we
> have it?

Once we've persuaded Linus, yes. :)

--STephen

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