[Yaffs-archive] Re: [YAFFS] slow performance --> Cache enabling

[Charles Manning]

On Thursday 01 May 2003 21:49, Sam Mason wrote:
> Charles Manning wrote:
> >Edward's feedback was a big suprise to me as I would have expected the
> > Linux cache to have done the job more effectively that the YAFFS cache.
>
> I guess I'm showing my ignorance here. . .  I've just had a quick look
> though the code, and it seems as though it doesn't need to use the
> Linux page cache.

By default configuration YAFFS uses (or at least should be) generic_file_read 
and generic_file_write which use the Linux page cache for caching. This can 
be controlled by disabling CONFIG_YAFFS_USE_GENERIC_RW.  If this caching is 
disabled (due to changing the config or a bug in the way I wrote the code), 
then using the in-YAFFS cache would provide a dramatic speedup.

What would suprise me is getting the speed increase by using both caches 
since I would expect the Linux page cache to effectively render the YAFFS 
cache useless.

>
> I presume that this has been discounted already.  But, I just know how
> many times I've spent days tracking down bugs, only to notice that
> some assumption I was making, was bogus.

Yes, I did make some assumptions that maybe were invalid. Thanx for pointing 
them out Sam.

-- Charles



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