lkml.org 
[lkml]   [2007]   [Jul]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH 1/6] compacting file_ra_state
Use 'unsigned int' instead of 'unsigned long' for the readahead indexes/sizes.

This helps reduce memory consumption on 64bit CPU when
a lot of files are opened.

Note that the (smaller) 32bit index can support up to 16PB file.
Which should be sufficient large at least for now.

Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
---
include/linux/fs.h | 10 +++++-----
mm/filemap.c | 2 +-
mm/readahead.c | 5 +++--
3 files changed, 9 insertions(+), 8 deletions(-)

--- linux-2.6.22-rc6-mm1.orig/include/linux/fs.h
+++ linux-2.6.22-rc6-mm1/include/linux/fs.h
@@ -771,16 +771,16 @@ struct fown_struct {
* Track a single file's readahead state
*/
struct file_ra_state {
- pgoff_t start; /* where readahead started */
- unsigned long size; /* # of readahead pages */
- unsigned long async_size; /* do asynchronous readahead when
+ unsigned int start; /* where readahead started */
+ unsigned int size; /* # of readahead pages */
+ unsigned int async_size; /* do asynchronous readahead when
there are only # of pages ahead */

- unsigned long ra_pages; /* Maximum readahead window */
+ unsigned int ra_pages; /* Maximum readahead window */
unsigned long mmap_hit; /* Cache hit stat for mmap accesses */
unsigned long mmap_miss; /* Cache miss stat for mmap accesses */
- unsigned long prev_index; /* Cache last read() position */
unsigned int prev_offset; /* Offset where last read() ended in a page */
+ unsigned int prev_index; /* Cache last read() position */
};

/*
--- linux-2.6.22-rc6-mm1.orig/mm/filemap.c
+++ linux-2.6.22-rc6-mm1/mm/filemap.c
@@ -840,7 +840,7 @@ static void shrink_readahead_size_eio(st
if (count > 5)
return;
count++;
- printk(KERN_WARNING "Reducing readahead size to %luK\n",
+ printk(KERN_WARNING "Reducing readahead size to %dK\n",
ra->ra_pages << (PAGE_CACHE_SHIFT - 10));
}

--- linux-2.6.22-rc6-mm1.orig/mm/readahead.c
+++ linux-2.6.22-rc6-mm1/mm/readahead.c
@@ -342,11 +342,12 @@ ondemand_readahead(struct address_space
bool hit_readahead_marker, pgoff_t offset,
unsigned long req_size)
{
- unsigned long max; /* max readahead pages */
+ int max; /* max readahead pages */
int sequential;

max = ra->ra_pages;
- sequential = (offset - ra->prev_index <= 1UL) || (req_size > max);
+ sequential = ((unsigned int)offset - ra->prev_index <= 1UL) ||
+ (req_size > max);

/*
* It's the expected callback offset, assume sequential access.
--
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-07-20 12:13    [W:0.067 / U:0.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site