Well, here it is.
I would like to know if this makes a big difference on highmem (2GB or
more) machines with heavy IO workloads.
I don't have such a machine here to be able to test it. (it works with a
1GB machine, but it needs to be tested with lots of highmem to show the
improvement)
diff -Nur linux.orig/fs/buffer.c linux/fs/buffer.c
--- linux.orig/fs/buffer.c Fri Mar 16 13:01:09 2001
+++ linux/fs/buffer.c Fri Mar 16 13:37:27 2001
@@ -2557,7 +2557,7 @@
as all dirty buffers lives _only_ in the DIRTY lru list.
As we never browse the LOCKED and CLEAN lru lists they are infact
completly useless. */
-static int flush_dirty_buffers(int check_flushtime)
+int flush_dirty_buffers(int check_flushtime, int lowmem)
{
struct buffer_head * bh, *next;
int flushed = 0, i;
@@ -2577,6 +2577,11 @@
if (buffer_locked(bh))
continue;
+#ifdef CONFIG_HIGHMEM
+ if (lowmem && PageHighMem(bh->b_page))
+ continue;
+#endif
+
if (check_flushtime) {
/* The dirty lru list is chronologically ordered so
if the current bh is not yet timed out,
@@ -2616,7 +2621,7 @@
wake_up_process(bdflush_tsk);
if (block)
- flush_dirty_buffers(0);
+ flush_dirty_buffers(0, 0);
}
}
@@ -2635,7 +2640,7 @@
sync_inodes(0);
unlock_kernel();
- flush_dirty_buffers(1);
+ flush_dirty_buffers(1, 0);
/* must really sync all the active I/O request to disk here */
run_task_queue(&tq_disk);
return 0;
@@ -2732,7 +2737,7 @@
for (;;) {
CHECK_EMERGENCY_SYNC
- flushed = flush_dirty_buffers(0);
+ flushed = flush_dirty_buffers(0, 0);
if (free_shortage())
flushed += page_launder(GFP_KERNEL, 0);
diff -Nur linux.orig/include/linux/fs.h linux/include/linux/fs.h
--- linux.orig/include/linux/fs.h Fri Mar 16 13:01:14 2001
+++ linux/include/linux/fs.h Fri Mar 16 13:36:57 2001
@@ -1288,6 +1288,7 @@
extern unsigned int get_hardblocksize(kdev_t);
extern struct buffer_head * bread(kdev_t, int, int);
extern void wakeup_bdflush(int wait);
+extern int flush_dirty_buffers(int, int);
extern int brw_page(int, struct page *, kdev_t, int [], int);
diff -Nur linux.orig/mm/highmem.c linux/mm/highmem.c
--- linux.orig/mm/highmem.c Fri Mar 16 13:01:13 2001
+++ linux/mm/highmem.c Fri Mar 16 13:44:01 2001
@@ -21,6 +21,7 @@
#include <linux/highmem.h>
#include <linux/swap.h>
#include <linux/slab.h>
+#include <linux/fs.h>
/*
* Virtual_count is not a pure "count".
@@ -280,9 +281,11 @@
if (page)
return page;
/*
- * No luck. First, kick the VM so it doesnt idle around while
- * we are using up our emergency rations.
+ * No luck. First, try to flush some low memory buffers.
+ * This will throttle highmem writes when low memory gets full.
*/
+ flush_dirty_buffers(0, 1);
+
wakeup_bdflush(0);
/*
@@ -317,9 +320,11 @@
if (bh)
return bh;
/*
- * No luck. First, kick the VM so it doesnt idle around while
- * we are using up our emergency rations.
+ * No luck. First, try to flush some low memory buffers.
+ * This will throttle highmem writes when low memory gets full.
*/
+ flush_dirty_buffers(0, 1);
+
wakeup_bdflush(0);
/*
-
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