Date: Sun, 4 Feb 1996 15:10:53 +0100 (MET) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: hackers@freebsd.org Subject: FAT filesystem performance Message-ID: <199602041410.PAA18920@labinfo.iet.unipi.it>
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Some time ago there was a discussion on the performance of FAT
filesystems. I think the conclusion was that it is not intrinsically
slow, it is just a problem of non optimal implementations which
tend not to keep the FAT in memory, and perhaps use synchronous writes.
Additionally, performance might probably benefit by an allocation
policy which privileges contiguity and locality for the blocks
belonging to the same file.
We use FAT filesystems both in the kernel, and in mtools.
For the latter, I thought there was a quick fix to the problem of
caching the FAT: just mmap the device, and the kernel will do caching
for you. Well, it does not look that simple, as the vast majority of
raw devices does not support mmap.
I am wondering: how hard would it be to add mmap() to, say, wd.c ?
Would it have other useful applications ?
Thanks
Luigi
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Luigi Rizzo Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it Universita' di Pisa
tel: +39-50-568533 via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522 http://www.iet.unipi.it/~luigi/
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