Re: Inactive memory keep growing and how to release it?

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On 03/14/2013 08:39 PM, Hillf Danton wrote:
On Sat, Mar 9, 2013 at 10:14 AM, Will Huck <will.huckk@xxxxxxxxx> wrote:
Cc experts. Hugh, Johannes,

On 03/04/2013 08:21 PM, Lenky Gao wrote:
2013/3/4 Zlatko Calusic <zlatko.calusic@xxxxxxxx>:
The drop_caches mechanism doesn't free dirty page cache pages. And your
bash
script is creating a lot of dirty pages. Run it like this and see if it
helps your case:

sync; echo 3 > /proc/sys/vm/drop_caches
Thanks for your advice.

The inactive memory still cannot be reclaimed after i execute the sync
command:

# cat /proc/meminfo | grep Inactive\(file\);
Inactive(file):   882824 kB
# sync;
# echo 3 > /proc/sys/vm/drop_caches
# cat /proc/meminfo | grep Inactive\(file\);
Inactive(file):   777664 kB

I find these page becomes orphaned in this function, but do not understand
why:

/*
   * If truncate cannot remove the fs-private metadata from the page, the
page
   * becomes orphaned.  It will be left on the LRU and may even be mapped
into
   * user pagetables if we're racing with filemap_fault().
   *
   * We need to bale out if page->mapping is no longer equal to the
original
   * mapping.  This happens a) when the VM reclaimed the page while we
waited on
   * its lock, b) when a concurrent invalidate_mapping_pages got there
first and
   * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
   */
static int
truncate_complete_page(struct address_space *mapping, struct page *page)
{
...

My file system type is ext3, mounted with the opteion data=journal and
it is easy to reproduce.

Perhaps we have to consider page count for orphan page if it
could be reproduced with mainline.

Why? /proc/sys/vm/drop_caches will call invalidate_mapping_pages() instead of truncate_complete_page().


Hillf
---
--- a/mm/vmscan.c	Sun Mar 10 13:36:26 2013
+++ b/mm/vmscan.c	Thu Mar 14 20:29:40 2013
@@ -315,14 +315,14 @@ out:
  	return ret;
  }

-static inline int is_page_cache_freeable(struct page *page)
+static inline int is_page_cache_freeable(struct page *page, int has_mapping)
  {
  	/*
  	 * A freeable page cache page is referenced only by the caller
  	 * that isolated the page, the page cache radix tree and
  	 * optional buffer heads at page->private.
  	 */
-	return page_count(page) - page_has_private(page) == 2;
+	return page_count(page) - page_has_private(page) == has_mapping + 1;
  }

page count 2 is for page cache and isolator, why you check mapping separately?

  static int may_write_to_queue(struct backing_dev_info *bdi,
@@ -393,7 +393,7 @@ static pageout_t pageout(struct page *pa
  	 * swap_backing_dev_info is bust: it doesn't reflect the
  	 * congestion state of the swapdevs.  Easy to fix, if needed.
  	 */
-	if (!is_page_cache_freeable(page))
+	if (!is_page_cache_freeable(page, mapping ? 1 : 0))
  		return PAGE_KEEP;
  	if (!mapping) {
  		/*
--

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