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SubjectRe: The cause of the "VM" performance problem with 2.4.X
"Van Maren, Kevin" wrote:
>
> It looks like the same patch as yesterday. Did you attach the wrong
> patch?

Drat, sorry - it's on the other machine. Here's a reconstruction:

--- linux-2.4.9/fs/buffer.c Thu Aug 16 12:23:19 2001
+++ linux-akpm/fs/buffer.c Thu Aug 23 10:15:41 2001
@@ -199,7 +199,7 @@ static void write_locked_buffers(struct
* return without it!
*/
#define NRSYNC (32)
-static int write_some_buffers(kdev_t dev)
+static int write_some_buffers(kdev_t dev, struct buffer_head **start_bh)
{
struct buffer_head *next;
struct buffer_head *array[NRSYNC];
@@ -207,6 +207,12 @@ static int write_some_buffers(kdev_t dev
int nr;

next = lru_list[BUF_DIRTY];
+ if (start_bh && *start_bh) {
+ if ((*start_bh)->b_list == BUF_DIRTY)
+ next = *start_bh;
+ brelse(*start_bh);
+ *start_bh = NULL;
+ }
nr = nr_buffers_type[BUF_DIRTY] * 2;
count = 0;
while (next && --nr >= 0) {
@@ -215,8 +221,11 @@ static int write_some_buffers(kdev_t dev

if (dev && bh->b_dev != dev)
continue;
- if (test_and_set_bit(BH_Lock, &bh->b_state))
+ if (test_and_set_bit(BH_Lock, &bh->b_state)) {
+ /* Shouldn't be on BUF_DIRTY */
+ __refile_buffer(bh);
continue;
+ }
if (atomic_set_buffer_clean(bh)) {
__refile_buffer(bh);
get_bh(bh);
@@ -224,6 +233,10 @@ static int write_some_buffers(kdev_t dev
if (count < NRSYNC)
continue;

+ if (start_bh && next) {
+ get_bh(next);
+ *start_bh = next;
+ }
spin_unlock(&lru_list_lock);
write_locked_buffers(array, count);
return -EAGAIN;
@@ -243,9 +256,11 @@ static int write_some_buffers(kdev_t dev
*/
static void write_unlocked_buffers(kdev_t dev)
{
+ struct buffer_head *start_bh = NULL;
do {
spin_lock(&lru_list_lock);
- } while (write_some_buffers(dev));
+ } while (write_some_buffers(dev, &start_bh));
+ brelse(start_bh);
run_task_queue(&tq_disk);
}

@@ -1116,14 +1131,14 @@ int balance_dirty_state(kdev_t dev)
*/
void balance_dirty(kdev_t dev)
{
- int state = balance_dirty_state(dev);
+ int state = balance_dirty_state(NODEV);

if (state < 0)
return;

/* If we're getting into imbalance, start write-out */
spin_lock(&lru_list_lock);
- write_some_buffers(dev);
+ write_some_buffers(NODEV, NULL);

/*
* And if we're _really_ out of balance, wait for
@@ -1132,8 +1147,9 @@ void balance_dirty(kdev_t dev)
* This will throttle heavy writers.
*/
if (state > 0) {
- wait_for_some_buffers(dev);
+ write_some_buffers(dev, NULL);
wakeup_bdflush();
+ wait_for_some_buffers(dev);
}
}

@@ -2607,7 +2623,7 @@ static int sync_old_buffers(void)
bh = lru_list[BUF_DIRTY];
if (!bh || time_before(jiffies, bh->b_flushtime))
break;
- if (write_some_buffers(NODEV))
+ if (write_some_buffers(NODEV, NULL))
continue;
return 0;
}
@@ -2706,7 +2722,7 @@ int bdflush(void *startup)
CHECK_EMERGENCY_SYNC

spin_lock(&lru_list_lock);
- if (!write_some_buffers(NODEV) || balance_dirty_state(NODEV) < 0) {
+ if (!write_some_buffers(NODEV, NULL) || balance_dirty_state(NODEV) < 0) {
wait_for_some_buffers(NODEV);
interruptible_sleep_on(&bdflush_wait);
}
-
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