From: Andrew Morton <akpm@linux-foundation.org>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org,
Wu Fengguang <fengguang.wu@intel.com>, Jan Kara <jack@suse.cz>,
Nick Piggin <npiggin@kernel.dk>,
Andrea Arcangeli <aarcange@redhat.com>,
Andi Kleen <ak@linux.intel.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>
Subject: Re: PAGE_CACHE_SIZE vs. PAGE_SIZE
Date: Thu, 31 Jan 2013 14:40:26 -0800 [thread overview]
Message-ID: <20130131144026.bd735c07.akpm@linux-foundation.org> (raw)
In-Reply-To: <20130118155724.GA8507@otc-wbsnb-06>
On Fri, 18 Jan 2013 17:57:25 +0200
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> 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 ;)
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WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org,
Wu Fengguang <fengguang.wu@intel.com>, Jan Kara <jack@suse.cz>,
Nick Piggin <npiggin@kernel.dk>,
Andrea Arcangeli <aarcange@redhat.com>,
Andi Kleen <ak@linux.intel.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>
Subject: Re: PAGE_CACHE_SIZE vs. PAGE_SIZE
Date: Thu, 31 Jan 2013 14:40:26 -0800 [thread overview]
Message-ID: <20130131144026.bd735c07.akpm@linux-foundation.org> (raw)
In-Reply-To: <20130118155724.GA8507@otc-wbsnb-06>
On Fri, 18 Jan 2013 17:57:25 +0200
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> 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 ;)
next prev parent reply other threads:[~2013-01-31 22:40 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-18 15:57 PAGE_CACHE_SIZE vs. PAGE_SIZE Kirill A. Shutemov
2013-01-31 22:40 ` Andrew Morton [this message]
2013-01-31 22:40 ` Andrew Morton
2013-02-19 16:12 ` Michel Lespinasse
2013-02-19 16:12 ` Michel Lespinasse
2013-02-19 10:32 ` Simon Jeons
2013-02-19 10:32 ` Simon Jeons
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