linux-kernel - Re: PAGE_CACHE_SIZE vs. PAGE

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Message-ID: <512354C4.2040705@gmail.com>
Date:	Tue, 19 Feb 2013 18:32:36 +0800
From:	Simon Jeons <simon.jeons@...il.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Nick Piggin <npiggin@...nel.dk>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andi Kleen <ak@...ux.intel.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>
Subject: Re: PAGE_CACHE_SIZE vs. PAGE_SIZE

On 01/18/2013 11:57 PM, Kirill A. Shutemov wrote:
> Hi,
>
> PAGE_CACHE_* macros were introduced long time ago in hope to implement
> page cache with larger chunks than one page in future.
>
> In fact it was never done.
>
> Some code paths assume PAGE_CACHE_SIZE <= PAGE_SIZE. E.g. we use
> zero_user_segments() to clear stale parts of page on cache filling, but
> the function is implemented only for individual small page.
>
> It's unlikely that global switch to PAGE_CACHE_SIZE > PAGE_SIZE will never
> happen since it will affect to much code at once.
>
> I think support of larger chunks in page cache can be in implemented in
> some form of THP with per-fs enabling.

IIRC, you try to implement THP support page cache, then PAGE_CACHE_SIZE 
maybe don't need any more.

>
> Is it time to get rid of PAGE_CACHE_* macros?
> I can prepare patchset if it's okay.
>

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