Re: Should PAGE_CACHE_SIZE be discarded?

[Benny Halevy <bhalevy@panasas.com>]

On Nov. 15, 2007, 14:05 +0200, David Howells <dhowells@redhat.com> wrote:
> Nick Piggin <npiggin@suse.de> wrote:
> 
>> It can be pretty well any power of 2 from PAGE_SIZE upwards, with
>> compound pages. None of the filesystems should really care at all.
>> It's not even a new concept, hugetlbfs uses HPAGE_SIZE...
> 
> Ummm... The filesystem has to care.  If the VFS/VM says 'fill this page' you
> do need to know how big the page is or whether it's even actually several
> pages.

I think that what Nick was trying to say is that PAGE_CACHE_SIZE should always
be used properly as the size of the memory struct Page covers (while PAGE_SIZE
is the hardware page size and the constraint is that PAGE_CACHE_SIZE == (PAGE_SIZE << k)
for some k >= 0).  If everybody does that then "None of the filesystems should really
care at all". That said, it doesn't seem like the current usage in fs/ and drivers/
is consistent with this convention.

> 
> David
> -