Messages in this thread |  | | Date | Thu, 18 Oct 2001 17:42:44 +0200 (CEST) | From | Kamil Iskra <> | Subject | Re: Poor floppy performance in kernel 2.4.10 |
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On Thu, 18 Oct 2001, Andreas Dilger wrote:
> > The behaviour is as if no caching was done, > > there is a slowdown by a factor of two. > I think this is a result of the "blockdev in pagecache" change added in > 2.4.10. One of the byproducts of this change is that if a block device > is closed (no other openers) then all of the pages from this device are > dropped from the cache. In the case of a floppy drive, this is very > important, as you don't want to be cacheing data from one floppy after > you have inserted a new floppy. > > In contrast, if you mounted the floppy instead of using mtools, it would > probably have good performance for small files as well.
That's very interesting. It would explain why it takes 2 seconds _every_ time you invoke "mdir", whereas before the invocations after the first one were more or less instantenous. And indeed, as you say, mounting a floppy does result in a good performance.
However, it does not explain why the first invocation is two times slower (it's 1 sec with kernel 2.4.9 and 2 secs with 2.4.10, the effect is even more visible for mcopy of a small file, like 30KB). I strace'd mdir and it's opening /dev/fd0 just once, at the beginning, and closing it at the end.
Regards,
-- Kamil Iskra http://www.science.uva.nl/~kamil/ Section Computational Science, Faculty of Science, Universiteit van Amsterdam kamil@science.uva.nl tel. +31 20 525 75 35 fax. +31 20 525 74 90 Kruislaan 403 room F.202 1098 SJ Amsterdam The Netherlands
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