2009-07-02 13:09:06

by Josef Bacik

Subject: [PATCH] mm: mark page accessed before we write_end

Hello,

In testing a backport of the write_begin/write_end AOPs, a 10% re-read
regression was noticed when running iozone. This regression was introduced
because the old AOPs would always do a mark_page_accessed(page) after the
commit_write, but when the new AOPs where introduced, the only place this was
kept was in pagecache_write_end(). This patch does the same thing in the
generic case as what is done in pagecache_write_end(), which is just to mark
the page accessed before we do write_end(). Thank you,

Signed-off-by: Josef Bacik <[email protected]>
---
mm/filemap.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 2239671..ccea3b6 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2272,6 +2272,7 @@ again:
pagefault_enable();
flush_dcache_page(page);

+ mark_page_accessed(page);
status = a_ops->write_end(file, mapping, pos, bytes, copied,
page, fsdata);
if (unlikely(status < 0))
--
1.5.4.3

2009-07-02 13:46:20

by Nick Piggin

Subject: Re: [PATCH] mm: mark page accessed before we write_end

On Thu, Jul 02, 2009 at 09:05:00AM -0400, Josef Bacik wrote:
> Hello,
>
> In testing a backport of the write_begin/write_end AOPs, a 10% re-read
> regression was noticed when running iozone. This regression was introduced
> because the old AOPs would always do a mark_page_accessed(page) after the
> commit_write, but when the new AOPs where introduced, the only place this was
> kept was in pagecache_write_end(). This patch does the same thing in the
> generic case as what is done in pagecache_write_end(), which is just to mark
> the page accessed before we do write_end(). Thank you,
>
> Signed-off-by: Josef Bacik <[email protected]>

Nasty bug. I'm sure (without looking at history) it's my fault :(
Good catch, thanks.

Acked-by: Nick Piggin <[email protected]>

> ---
> mm/filemap.c | 1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 2239671..ccea3b6 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2272,6 +2272,7 @@ again:
> pagefault_enable();
> flush_dcache_page(page);
>
> + mark_page_accessed(page);
> status = a_ops->write_end(file, mapping, pos, bytes, copied,
> page, fsdata);
> if (unlikely(status < 0))
> --
> 1.5.4.3