Re: [2.4.17/18pre] VM and swap - it's really unusable

Andrew Morton
2002-01-12T20:29:31Z

Ed Sweetman wrote:
>
> If you want to test the preempt kernel you're going to need something that
> can find the mean latancy or "time to action" for a particular program or
> all programs being run at the time and then run multiple programs that you
> would find on various peoples' systems. That is the "feel" people talk
> about when they praise the preempt patch.

Right. And that is precisely why I created the "mini-ll" patch. To
give the improved "feel" in a way which is acceptable for merging into
the 2.4 kernel.

And guess what? Nobody has tested the damn thing, so it's going
nowhere.

Here it is again:

--- linux-2.4.18-pre3/fs/buffer.c Fri Dec 21 11:19:14 2001
+++ linux-akpm/fs/buffer.c Sat Jan 12 12:22:29 2002
@@ -249,12 +249,19 @@ static int wait_for_buffers(kdev_t dev,
struct buffer_head * next;
int nr;

- next = lru_list[index];
nr = nr_buffers_type[index];
+repeat:
+ next = lru_list[index];
while (next && --nr >= 0) {
struct buffer_head *bh = next;
next = bh->b_next_free;

+ if (dev == NODEV && current->need_resched) {
+ spin_unlock(&lru_list_lock);
+ conditional_schedule();
+ spin_lock(&lru_list_lock);
+ goto repeat;
+ }
if (!buffer_locked(bh)) {
if (refile)
__refile_buffer(bh);
@@ -1174,8 +1181,10 @@ struct buffer_head * bread(kdev_t dev, i

bh = getblk(dev, block, size);
touch_buffer(bh);
- if (buffer_uptodate(bh))
+ if (buffer_uptodate(bh)) {
+ conditional_schedule();
return bh;
+ }
ll_rw_block(READ, 1, &bh);
wait_on_buffer(bh);
if (buffer_uptodate(bh))
--- linux-2.4.18-pre3/fs/dcache.c Fri Dec 21 11:19:14 2001
+++ linux-akpm/fs/dcache.c Sat Jan 12 12:22:29 2002
@@ -71,7 +71,7 @@ static inline void d_free(struct dentry
* d_iput() operation if defined.
* Called with dcache_lock held, drops it.
*/
-static inline void dentry_iput(struct dentry * dentry)
+static void dentry_iput(struct dentry * dentry)
{
struct inode *inode = dentry->d_inode;
if (inode) {
@@ -84,6 +84,7 @@ static inline void dentry_iput(struct de
iput(inode);
} else
spin_unlock(&dcache_lock);
+ conditional_schedule();
}

/*
--- linux-2.4.18-pre3/fs/jbd/commit.c Fri Dec 21 11:19:14 2001
+++ linux-akpm/fs/jbd/commit.c Sat Jan 12 12:22:29 2002
@@ -212,6 +212,16 @@ write_out_data_locked:
__journal_remove_journal_head(bh);
refile_buffer(bh);
__brelse(bh);
+ if (current->need_resched) {
+ if (commit_transaction->t_sync_datalist)
+ commit_transaction->t_sync_datalist =
+ next_jh;
+ if (bufs)
+ break;
+ spin_unlock(&journal_datalist_lock);
+ conditional_schedule();
+ goto write_out_data;
+ }
}
}
if (bufs == ARRAY_SIZE(wbuf)) {
--- linux-2.4.18-pre3/fs/proc/array.c Thu Oct 11 09:00:01 2001
+++ linux-akpm/fs/proc/array.c Sat Jan 12 12:22:29 2002
@@ -415,6 +415,8 @@ static inline void statm_pte_range(pmd_t
pte_t page = *pte;
struct page *ptpage;

+ conditional_schedule();
+
address += PAGE_SIZE;
pte++;
if (pte_none(page))
--- linux-2.4.18-pre3/fs/proc/generic.c Fri Sep 7 10:53:59 2001
+++ linux-akpm/fs/proc/generic.c Sat Jan 12 12:22:29 2002
@@ -98,7 +98,9 @@ proc_file_read(struct file * file, char
retval = n;
break;
}
-
+
+ conditional_schedule();
+
/* This is a hack to allow mangling of file pos independent
* of actual bytes read. Simply place the data at page,
* return the bytes, and set `start' to the desired offset
--- linux-2.4.18-pre3/include/linux/condsched.h Thu Jan 1 00:00:00 1970
+++ linux-akpm/include/linux/condsched.h Sat Jan 12 12:22:29 2002
@@ -0,0 +1,18 @@
+#ifndef _LINUX_CONDSCHED_H
+#define _LINUX_CONDSCHED_H
+
+#ifndef __LINUX_COMPILER_H
+#include <linux/compiler.h>
+#endif
+
+#ifndef __ASSEMBLY__
+#define conditional_schedule() \
+do { \
+ if (unlikely(current->need_resched)) { \
+ __set_current_state(TASK_RUNNING); \
+ schedule(); \
+ } \
+} while(0)
+#endif
+
+#endif
--- linux-2.4.18-pre3/include/linux/sched.h Fri Dec 21 11:19:23 2001
+++ linux-akpm/include/linux/sched.h Sat Jan 12 12:22:29 2002
@@ -13,6 +13,7 @@ extern unsigned long event;
#include <linux/times.h>
#include <linux/timex.h>
#include <linux/rbtree.h>
+#include <linux/condsched.h>

#include <asm/system.h>
#include <asm/semaphore.h>
--- linux-2.4.18-pre3/mm/filemap.c Thu Jan 10 13:39:50 2002
+++ linux-akpm/mm/filemap.c Sat Jan 12 12:22:29 2002
@@ -296,10 +296,7 @@ static int truncate_list_pages(struct li

page_cache_release(page);

- if (current->need_resched) {
- __set_current_state(TASK_RUNNING);
- schedule();
- }
+ conditional_schedule();

spin_lock(&pagecache_lock);
goto restart;
@@ -609,6 +606,7 @@ void filemap_fdatasync(struct address_sp
UnlockPage(page);

page_cache_release(page);
+ conditional_schedule();
spin_lock(&pagecache_lock);
}
spin_unlock(&pagecache_lock);
@@ -1392,6 +1390,9 @@ page_ok:
offset &= ~PAGE_CACHE_MASK;

page_cache_release(page);
+
+ conditional_schedule();
+
if (ret == nr && desc->count)
continue;
break;
@@ -3025,6 +3026,8 @@ unlock:
SetPageReferenced(page);
UnlockPage(page);
page_cache_release(page);
+
+ conditional_schedule();

if (status < 0)
break;
--- linux-2.4.18-pre3/drivers/block/ll_rw_blk.c Thu Jan 10 13:39:49 2002
+++ linux-akpm/drivers/block/ll_rw_blk.c Sat Jan 12 12:22:29 2002
@@ -917,6 +917,7 @@ void submit_bh(int rw, struct buffer_hea
kstat.pgpgin += count;
break;
}
+ conditional_schedule();
}

/**