Messages in this thread | | | From | "Peter T. Breuer" <> | Subject | Re: (fwd) Re: [RFC] mount flag "direct" | Date | Fri, 6 Sep 2002 11:17:05 +0200 (MET DST) |
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"Anton Altaparmakov wrote:" > At 09:57 06/09/02, Peter T. Breuer wrote: > >"Anton Altaparmakov wrote:" > >I've had a look now. I concur that e2fs at least is full of assumptions > >that it has various different sorts of metadata in memory at all times. > >I can't rewrite that, or even add a "warning will robinson" callback to > >vfs, as I intended. What I can do, I think, is .. > > Oh, you saw the light. (-: I can assure you that most file systems make
The question is if they do it in a way I can read. If I can read it, I can fix it. There was too much noise inside e2fs to see a point or points of intercept. So the intercept has to be higher, and ..
> direct_IO, I plan to keep all metadata caching in place, just stop caching > the actual file data. That should give maximum performance I think.
But not correct behaviour wrt metadata in a shared disk fs. And your calculation of "maximum performance" is off. Look, you seem to forget this:
suppose that I make the FS twice as slow as before by meddling with it to make it sharable
then I simply share it among 4 nodes to get a two times _speed up_ overall.
That's the basic idea. Details left to reader.
I.e. I don't care if it gets slower. We are talking thousands of nodes here. Only the detail of the topology is affected by the real numbers.
> >.. simply do a dput of the fs root directory from time to time, from > >vfs - whenever I think it is appropriate. As far as I can see from my > >quick look that may cause the dcache path off that to be GC'ed. And > >that may be enough to do a few experiments for O_DIRDIRECT. > > What does "GC" mean?
Garbage collection. I assume that either there is a point at which the dcache is swept or as I free a dentry from the cache its dependents are swept. I don't know which. Feel free to enlighten me. My question is simply "is doing a dput of the base directory dentry on the FS enough to clear the dcache for that FS"?
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