On Tue, 25 Sep 2007 12:13:41 +0200
Jan Kundrát <[email protected]> wrote:
> Rik van Riel wrote:
> > How much memory did you have in "cached" when you looked
> > with top (and no swap enabled) ?
>
> Hi Rik,
> it was pretty low number (several thousands, or maybe tens of
> thousands).
>
> In the meanwhile, I've come across your patch [1] ("prevent kswapd
> from freeing excessive amounts of lowmem") and applied it locally.
Could you try out the attached patch, too?
Kswapd and try_to_free_pages() have a built-in pause, where
it waits for IO to complete. However, the current code also
calls blk_congestion_wait() when there is no IO in flight!
This patch should only make the pageout code wait for IO when
there actually is a significant amount of pageout IO in flight.
Signed-off-by: Rik van Riel <[email protected]>
diff -up linux-2.6.22.x86_64/mm/vmscan.c.wait linux-2.6.22.x86_64/mm/vmscan.c
--- linux-2.6.22.x86_64/mm/vmscan.c.wait 2007-09-25 11:33:30.000000000 -0400
+++ linux-2.6.22.x86_64/mm/vmscan.c 2007-09-25 21:27:08.000000000 -0400
@@ -68,6 +68,8 @@ struct scan_control {
int all_unreclaimable;
int order;
+
+ int nr_io_pages;
};
#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
@@ -489,8 +491,10 @@ static unsigned long shrink_page_list(st
*/
if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
wait_on_page_writeback(page);
- else
+ else {
+ sc->nr_io_pages++;
goto keep_locked;
+ }
}
referenced = page_referenced(page, 1);
@@ -541,8 +545,10 @@ static unsigned long shrink_page_list(st
case PAGE_ACTIVATE:
goto activate_locked;
case PAGE_SUCCESS:
- if (PageWriteback(page) || PageDirty(page))
+ if (PageWriteback(page) || PageDirty(page)) {
+ sc->nr_io_pages++;
goto keep;
+ }
/*
* A synchronous write - probably a ramdisk. Go
* ahead and try to reclaim the page.
@@ -1201,6 +1207,7 @@ unsigned long try_to_free_pages(struct z
for (priority = DEF_PRIORITY; priority >= 0; priority--) {
sc.nr_scanned = 0;
+ sc.nr_io_pages = 0;
if (!priority)
disable_swap_token();
nr_reclaimed += shrink_zones(priority, zones, &sc);
@@ -1229,7 +1236,8 @@ unsigned long try_to_free_pages(struct z
}
/* Take a nap, wait for some writeback to complete */
- if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
+ if (sc.nr_scanned && priority < DEF_PRIORITY - 2 &&
+ sc.nr_io_pages > sc.swap_cluster_max)
congestion_wait(WRITE, HZ/10);
}
/* top priority shrink_caches still had more to do? don't OOM, then */
@@ -1315,6 +1323,7 @@ loop_again:
if (!priority)
disable_swap_token();
+ sc.nr_io_pages = 0;
all_zones_ok = 1;
/*
@@ -1398,7 +1407,8 @@ loop_again:
* OK, kswapd is getting into trouble. Take a nap, then take
* another pass across the zones.
*/
- if (total_scanned && priority < DEF_PRIORITY - 2)
+ if (total_scanned && priority < DEF_PRIORITY - 2 &&
+ sc.nr_io_pages > sc.swap_cluster_max)
congestion_wait(WRITE, HZ/10);
/*
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