[Patch 1/2] 2.6.15-rc1-mm2: disabling the pagecache for doingbenchmarks

From: Dirk Henning Gerdes
Date: Sat Nov 19 2005 - 11:41:32 EST


The changes in the do_generic-mapping_read function...



Signed-off-by: Dirk Gerdes
--


--- linux-2.6.15-rc1-mm2/mm/filemap.c 2005-11-19 12:31:43.000000000
+0100
+++ linux-2.6.15-rc1-mm2-pagecache/mm/filemap.c 2005-11-19 13:29:44.000000000 +0100
@@ -738,6 +738,55 @@ grab_cache_page_nowait(struct address_sp

EXPORT_SYMBOL(grab_cache_page_nowait);

+
+
+
+void make_page_not_uptodate(struct page *page)
+{
+ struct buffer_head *bh, *first;
+ //printk("make_page_not_uptodate_called\n");
+ lock_page(page);
+ if(!PageDirty(page)){
+ ClearPageUptodate(page);
+ if (page_has_buffers(page)){
+ bh = page_buffers(page);
+ first = bh;
+ do{
+ lock_buffer(bh);
+ if(!buffer_dirty(bh)){
+ clear_buffer_uptodate(bh);
+ }
+ unlock_buffer(bh);
+
+ bh=bh->b_this_page;
+
+ }while(bh != first);
+ }
+ }
+ unlock_page(page);
+ release_pages(&page, 1, 0);
+}
+
+int pagecache = 1; // bool pagecache on / off
+ // 1 : on
+ // 2 : off
+EXPORT_SYMBOL(pagecache);
+
+
+
/*
* This is a generic file read routine, and uses the
* mapping->a_ops->readpage() function for the actual low-level
@@ -765,6 +814,7 @@ void do_generic_mapping_read(struct addr
unsigned long prev_index;
loff_t isize;
struct page *cached_page;
+ struct page *foundpage = NULL;
int error;
struct file_ra_state ra = *_ra;

@@ -780,6 +830,17 @@ void do_generic_mapping_read(struct addr
goto out;

end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
+
+/**
+if the needed page is in Page Cache its PageUptodate-Bit is cleared, so it have to be read again
+*/
+ if (pagecache == 0){
+ foundpage = find_get_page(mapping,index);
+ if (foundpage != NULL){
+ make_page_not_uptodate(foundpage);
+ }
+ }
+
for (;;) {
struct page *page;
unsigned long nr, ret;
@@ -797,9 +858,12 @@ void do_generic_mapping_read(struct addr
nr = nr - offset;

cond_resched();
- if (index == next_index)
- next_index = page_cache_readahead(mapping, &ra, filp,
- index, last_index - index);
+
+/**page_cache_readahead should only be used, if pagecache is activated */
+ if (pagecache){
+ if (index == next_index)
+ next_index = page_cache_readahead(mapping, &ra, filp,index, last_index - index);
+ }

find_page:
page = find_get_page(mapping, index);
@@ -842,8 +906,15 @@ page_ok:
offset &= ~PAGE_CACHE_MASK;

page_cache_release(page);
- if (ret == nr && desc->count)
+ if (ret == nr && desc->count){
+ if (pagecache == 0){
+ foundpage = find_get_page(mapping,index);
+ if (foundpage != NULL){
+ make_page_not_uptodate(foundpage);
+ }
+ }
continue;
+ }
goto out;

page_not_up_to_date:

-
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