Re: [PATCH 11/15] writeback: skip balance_dirty_pages() for in-memory fs

Wu Fengguang
2011-06-11T13:07:37Z

> @@ -495,6 +490,9 @@ static void balance_dirty_pages(struct a
> bool dirty_exceeded = false;
> struct backing_dev_info *bdi = mapping->backing_dev_info;
>
> + if (!bdi_cap_account_dirty(bdi))
> + return;
> +
> for (;;) {
> struct writeback_control wbc = {
> .sync_mode = WB_SYNC_NONE,
>

Update: it's slightly better to do early return in
balance_dirty_pages_ratelimited_nr(). This way the tmpfs dirties won't
unnecessarily disturb the per-cpu bdp_ratelimits counters.

Thanks,
Fengguang
---

--- linux-next.orig/mm/page-writeback.c 2011-06-11 17:52:59.000000000 +0800
+++ linux-next/mm/page-writeback.c 2011-06-11 17:53:53.000000000 +0800
@@ -1098,9 +1098,6 @@ static void balance_dirty_pages(struct a
struct backing_dev_info *bdi = mapping->backing_dev_info;
unsigned long start_time = jiffies;

- if (!bdi_cap_account_dirty(bdi))
- return;
-
for (;;) {
nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS);
@@ -1237,9 +1234,13 @@ static DEFINE_PER_CPU(unsigned long, bdp
void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
unsigned long nr_pages_dirtied)
{
+ struct backing_dev_info *bdi = mapping->backing_dev_info;
unsigned long ratelimit;
unsigned long *p;

+ if (!bdi_cap_account_dirty(bdi))
+ return;
+
ratelimit = ratelimit_pages;
if (mapping->backing_dev_info->dirty_exceeded)
ratelimit = 8;