Messages in this thread |  | | Date | Thu, 18 Oct 2001 19:17:32 +0300 | From | Ville Herva <> | Subject | Re: Poor floppy performance in kernel 2.4.10 |
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On Thu, Oct 18, 2001 at 05:42:44PM +0200, you [Kamil Iskra] claimed: > 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.
That's propably beacause it syncs the writes on close().
Perhaps you could try the trick Linus suggested in another thread, namely:
sleep 1000 < /dev/fd0 &
mdir mcopy mdir mcopy <do whatever>
kill %1
That keeps one (dummy) reference to the floppy device open until you're done using it.
-- v --
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