From: Nick Piggin <nickpiggin@yahoo.com.au>
Use a bit spin lock in the first buffer of the page to synchronise asynch
IO buffer completions, instead of the global page_uptodate_lock, which is
showing some scalabilty problems.
Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
fs/buffer.c | 25 +++++++++++++++++--------
include/linux/buffer_head.h | 3 +++
2 files changed, 20 insertions(+), 8 deletions(-)
diff -puN fs/buffer.c~page_uptodate-locking-scalability fs/buffer.c
--- devel/fs/buffer.c~page_uptodate-locking-scalability 2005-06-29 18:15:27.000000000 -0700
+++ devel-akpm/fs/buffer.c 2005-06-29 18:18:11.000000000 -0700
@@ -513,8 +513,8 @@ static void free_more_memory(void)
*/
static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
{
- static DEFINE_SPINLOCK(page_uptodate_lock);
unsigned long flags;
+ struct buffer_head *first;
struct buffer_head *tmp;
struct page *page;
int page_uptodate = 1;
@@ -536,7 +536,9 @@ static void end_buffer_async_read(struct
* two buffer heads end IO at almost the same time and both
* decide that the page is now completely done.
*/
- spin_lock_irqsave(&page_uptodate_lock, flags);
+ first = page_buffers(page);
+ local_irq_save(flags);
+ bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
clear_buffer_async_read(bh);
unlock_buffer(bh);
tmp = bh;
@@ -549,7 +551,8 @@ static void end_buffer_async_read(struct
}
tmp = tmp->b_this_page;
} while (tmp != bh);
- spin_unlock_irqrestore(&page_uptodate_lock, flags);
+ bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
+ local_irq_restore(flags);
/*
* If none of the buffers had errors and they are all
@@ -561,7 +564,8 @@ static void end_buffer_async_read(struct
return;
still_busy:
- spin_unlock_irqrestore(&page_uptodate_lock, flags);
+ bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
+ local_irq_restore(flags);
return;
}
@@ -572,8 +576,8 @@ still_busy:
void end_buffer_async_write(struct buffer_head *bh, int uptodate)
{
char b[BDEVNAME_SIZE];
- static DEFINE_SPINLOCK(page_uptodate_lock);
unsigned long flags;
+ struct buffer_head *first;
struct buffer_head *tmp;
struct page *page;
@@ -594,7 +598,10 @@ void end_buffer_async_write(struct buffe
SetPageError(page);
}
- spin_lock_irqsave(&page_uptodate_lock, flags);
+ first = page_buffers(page);
+ local_irq_save(flags);
+ bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
+
clear_buffer_async_write(bh);
unlock_buffer(bh);
tmp = bh->b_this_page;
@@ -605,12 +612,14 @@ void end_buffer_async_write(struct buffe
}
tmp = tmp->b_this_page;
}
- spin_unlock_irqrestore(&page_uptodate_lock, flags);
+ bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
+ local_irq_restore(flags);
end_page_writeback(page);
return;
still_busy:
- spin_unlock_irqrestore(&page_uptodate_lock, flags);
+ bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
+ local_irq_restore(flags);
return;
}
diff -puN include/linux/buffer_head.h~page_uptodate-locking-scalability include/linux/buffer_head.h
--- devel/include/linux/buffer_head.h~page_uptodate-locking-scalability 2005-06-29 18:15:27.000000000 -0700
+++ devel-akpm/include/linux/buffer_head.h 2005-06-29 18:16:07.000000000 -0700
@@ -19,6 +19,9 @@ enum bh_state_bits {
BH_Dirty, /* Is dirty */
BH_Lock, /* Is locked */
BH_Req, /* Has been submitted for I/O */
+ BH_Uptodate_Lock,/* Used by the first bh in a page, to serialise
+ * IO completion of other buffers in the page
+ */
BH_Mapped, /* Has a disk mapping */
BH_New, /* Disk mapping was newly created by get_block */
_