Messages in this thread | | | Date | Thu, 28 Sep 2006 18:09:33 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: [NFS] [PATCH 009 of 11] knfsd: Allow max size of NFSd payload to be configured. |
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On Thu, 28 Sep 2006, Neil Brown wrote: > But are the pages that totalram is measure in, normal pages, of > page_cache pages? And is there a difference?
There's never yet been a difference, outside of some patches by bcrl. But totalram_pages comes "before" any idea of page cache, so it's in normal pages.
> Should we use PAGE_CACHE_SHIFT, or PAGE_SHIFT?
PAGE_SHIFT.
> And why do we have both if they are numerically identical?
Very irritating: the time I've wasted on "correcting" code for the "difference" between them! Yet there's still plenty wrong and I've largely given up on it.
Probably never will be a difference: but the idea was that the page cache might use >0-order pages (unclear what happens to swap cache).
I wish they'd waited for a working implementation before introducing the distinction; but never quite felt like deleting all trace of it.
> > I'll submit a patch which uses > 12 - PAGE_SHIFT > in a little while.
I haven't seen your context; but "12 - PAGE_SHIFT" sounds like a bad idea on all those architectures with PAGE_SHIFT 13 or more; you'll be on much safer ground working with "PAGE_SHIFT - 12".
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