From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx147.postini.com [74.125.245.147]) by kanga.kvack.org (Postfix) with SMTP id 0F8586B000E for ; Thu, 31 Jan 2013 17:40:27 -0500 (EST) Date: Thu, 31 Jan 2013 14:40:26 -0800 From: Andrew Morton Subject: Re: PAGE_CACHE_SIZE vs. PAGE_SIZE Message-Id: <20130131144026.bd735c07.akpm@linux-foundation.org> In-Reply-To: <20130118155724.GA8507@otc-wbsnb-06> References: <20130118155724.GA8507@otc-wbsnb-06> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: Linus Torvalds , Al Viro , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Wu Fengguang , Jan Kara , Nick Piggin , Andrea Arcangeli , Andi Kleen , "Kirill A. Shutemov" On Fri, 18 Jan 2013 17:57:25 +0200 "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. > > Is it time to get rid of PAGE_CACHE_* macros? > I can prepare patchset if it's okay. The distinct PAGE_CACHE_SIZE has never been used for anything, but I do kinda like it for documentary reasons: PAGE_SIZE is a raw, low-level thing and PAGE_CACHE_SIZE is the specialized we're-doing-pagecache-stuff thing. But I'm sure I could get used to not having it ;) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org