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[PATCH] page_uptodate locking scalability 

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>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Nick Piggin 2005-07-07 17:56:56 -07:00 committed by Linus Torvalds
parent d6afe27bff
commit a39722034a
2 changed files with 20 additions and 8 deletions
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25
fs/buffer.c
View File

@ -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 buffer_head *bh, int uptodate)
* 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 buffer_head *bh, int uptodate)
}
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 buffer_head *bh, int uptodate)
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 buffer_head *bh, int uptodate)
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 buffer_head *bh, int uptodate)
}
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;
}

3
include/linux/buffer_head.h
View File

@ -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 */