On Thu, 18 Aug 2011 00:38:49 -0700
Greg Thelen [off-list ref] wrote:

KAMEZAWA Hiroyuki [off-list ref] writes:

quoted

On Thu, 18 Aug 2011 00:10:56 -0700
Greg Thelen [off-list ref] wrote:

quoted

KAMEZAWA Hiroyuki [off-list ref] writes:

quoted

On Wed, 17 Aug 2011 09:15:03 -0700
Greg Thelen [off-list ref] wrote:

quoted

When the system is under background dirty memory threshold but some
cgroups are over their background dirty memory thresholds, then only
writeback inodes associated with the over-limit cgroups.

In addition to checking if the system dirty memory usage is over the
system background threshold, over_bground_thresh() now checks if any
cgroups are over their respective background dirty memory thresholds.

If over-limit cgroups are found, then the new
wb_writeback_work.for_cgroup field is set to distinguish between system
and memcg overages.  The new wb_writeback_work.shared_inodes field is
also set.  Inodes written by multiple cgroup are marked owned by
I_MEMCG_SHARED rather than a particular cgroup.  Such shared inodes
cannot easily be attributed to a cgroup, so per-cgroup writeback
(futures version of wakeup_flusher_threads and balance_dirty_pages)
performs suboptimally in the presence of shared inodes.  Therefore,
write shared inodes when performing cgroup background writeback.

If performing cgroup writeback, move_expired_inodes() skips inodes that
do not contribute dirty pages to the cgroup being written back.

After writing some pages, wb_writeback() will call
mem_cgroup_writeback_done() to update the set of over-bg-limits memcg.

This change also makes wakeup_flusher_threads() memcg aware so that
per-cgroup try_to_free_pages() is able to operate more efficiently
without having to write pages of foreign containers.  This change adds a
mem_cgroup parameter to wakeup_flusher_threads() to allow callers,
especially try_to_free_pages() and foreground writeback from
balance_dirty_pages(), to specify a particular cgroup to write inodes
from.

Signed-off-by: Greg Thelen <redacted>
---
Changelog since v8:

- Added optional memcg parameter to __bdi_start_writeback(),
  bdi_start_writeback(), wakeup_flusher_threads(), writeback_inodes_wb().

- move_expired_inodes() now uses pass in struct wb_writeback_work instead of
  struct writeback_control.

- Added comments to over_bground_thresh().

 fs/buffer.c               |    2 +-
 fs/fs-writeback.c         |   96 +++++++++++++++++++++++++++++++++-----------
 fs/sync.c                 |    2 +-
 include/linux/writeback.h |    6 ++-
 mm/backing-dev.c          |    3 +-
 mm/page-writeback.c       |    3 +-
 mm/vmscan.c               |    3 +-
 7 files changed, 84 insertions(+), 31 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index dd0220b..da1fb23 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c

@@ -293,7 +293,7 @@ static void free_more_memory(void)
 	struct zone *zone;
 	int nid;
 
-	wakeup_flusher_threads(1024);
+	wakeup_flusher_threads(1024, NULL);
 	yield();
 
 	for_each_online_node(nid) {

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index e91fb82..ba55336 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c

@@ -38,10 +38,14 @@ struct wb_writeback_work {
 	struct super_block *sb;
 	unsigned long *older_than_this;
 	enum writeback_sync_modes sync_mode;
+	unsigned short memcg_id;	/* If non-zero, then writeback specified
+					 * cgroup. */
 	unsigned int tagged_writepages:1;
 	unsigned int for_kupdate:1;
 	unsigned int range_cyclic:1;
 	unsigned int for_background:1;
+	unsigned int for_cgroup:1;	/* cgroup writeback */
+	unsigned int shared_inodes:1;	/* write inodes spanning cgroups */
 
 	struct list_head list;		/* pending work list */
 	struct completion *done;	/* set if the caller waits */

@@ -114,9 +118,12 @@ static void bdi_queue_work(struct backing_dev_info *bdi,
 	spin_unlock_bh(&bdi->wb_lock);
 }
 
+/*
+ * @memcg is optional.  If set, then limit writeback to the specified cgroup.
+ */
 static void
 __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
-		      bool range_cyclic)
+		      bool range_cyclic, struct mem_cgroup *memcg)
 {
 	struct wb_writeback_work *work;
 

@@ -136,6 +143,8 @@ __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
 	work->sync_mode	= WB_SYNC_NONE;
 	work->nr_pages	= nr_pages;
 	work->range_cyclic = range_cyclic;
+	work->memcg_id = memcg ? css_id(mem_cgroup_css(memcg)) : 0;
+	work->for_cgroup = memcg != NULL;
 

I couldn't find a patch for mem_cgroup_css(NULL). Is it in patch 1-10 ?
Other parts seems ok to me.


Thanks,
-Kame

Mainline commit d324236b3333e87c8825b35f2104184734020d35 adds
mem_cgroup_css() to memcontrol.c.  The above code does not call
mem_cgroup_css() with a NULL parameter due to the 'memcg ? ...' check.
So I do not think any additional changes to mem_cgroup_css() are needed.
Am I missing your point?

I thought you need
==
struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *mem)
{
+	if (!mem)
+		return NULL;
       return &mem->css;
}
==
And
==
unsigned short css_id(struct cgroup_subsys_state *css)
{
        struct css_id *cssid;

+	if (!css)
		return 0;
}
==

Thanks,
-Kame

I think that your changes to mem_cgroup_css() and css_id() are
unnecessary for my patches because my patches do not call
mem_cgroup_css(NULL).  The "?" check below prevents NULL from being
passed into mem_cgroup_css():

+	work->memcg_id = memcg ? css_id(mem_cgroup_css(memcg)) : 0;

Ah, I see. Thank you for clarification.


Thanks,
-Kame

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>