If the current process is in a non-root memcg, then
balance_dirty_pages() will consider the memcg dirty limits as well as
the system-wide limits. This allows different cgroups to have distinct
dirty limits which trigger direct and background writeback at different
levels.
If called with a mem_cgroup, then throttle_vm_writeout() queries the
given cgroup for its dirty memory usage limits.
Signed-off-by: Andrea Righi <andrea@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Thelen <gthelen@xxxxxxxxxx>
---
Changelog since v8:
- Use 'memcg' rather than 'mem' for local variables and parameters.
This is consistent with other memory controller code.
include/linux/writeback.h | 2 +-
mm/page-writeback.c | 35 +++++++++++++++++++++++++++++------
mm/vmscan.c | 2 +-
3 files changed, 31 insertions(+), 8 deletions(-)
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index e6790e8..0f809e3 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -116,7 +116,7 @@ void laptop_mode_timer_fn(unsigned long data);
#else
static inline void laptop_sync_completion(void) { }
#endif
-void throttle_vm_writeout(gfp_t gfp_mask);
+void throttle_vm_writeout(gfp_t gfp_mask, struct mem_cgroup *memcg);
extern unsigned long global_dirty_limit;
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 64de98c..9ce199d 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -645,7 +645,8 @@ static void bdi_update_bandwidth(struct backing_dev_info *bdi,
* data. It looks at the number of dirty pages in the machine and will force
* the caller to perform writeback if the system is over `vm_dirty_ratio'.
* If we're over `background_thresh' then the writeback threads are woken to
- * perform some writeout.
+ * perform some writeout. The current task may belong to a cgroup with
+ * dirty limits, which are also checked.
*/
static void balance_dirty_pages(struct address_space *mapping,
unsigned long write_chunk)
@@ -665,6 +666,8 @@ static void balance_dirty_pages(struct address_space *mapping,
struct backing_dev_info *bdi = mapping->backing_dev_info;
unsigned long start_time = jiffies;
+ mem_cgroup_balance_dirty_pages(mapping, write_chunk);
+
for (;;) {
nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS);
@@ -856,23 +859,43 @@ void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
}
EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
-void throttle_vm_writeout(gfp_t gfp_mask)
+/*
+ * Throttle the current task if it is near dirty memory usage limits. Both
+ * global dirty memory limits and (if @memcg is given) per-cgroup dirty memory
+ * limits are checked.
+ *
+ * If near limits, then wait for usage to drop. Dirty usage should drop because
+ * dirty producers should have used balance_dirty_pages(), which would have
+ * scheduled writeback.
+ */
+void throttle_vm_writeout(gfp_t gfp_mask, struct mem_cgroup *memcg)
{
unsigned long background_thresh;
unsigned long dirty_thresh;
+ struct dirty_info memcg_info;
+ bool do_memcg;
for ( ; ; ) {
global_dirty_limits(&background_thresh, &dirty_thresh);
+ do_memcg = memcg &&
+ mem_cgroup_hierarchical_dirty_info(
+ determine_dirtyable_memory(), memcg,
+ &memcg_info);
/*
* Boost the allowable dirty threshold a bit for page
* allocators so they don't get DoS'ed by heavy writers
*/
dirty_thresh += dirty_thresh / 10; /* wheeee... */
-
- if (global_page_state(NR_UNSTABLE_NFS) +
- global_page_state(NR_WRITEBACK) <= dirty_thresh)
- break;
+ if (do_memcg)
+ memcg_info.dirty_thresh += memcg_info.dirty_thresh / 10;
+
+ if ((global_page_state(NR_UNSTABLE_NFS) +
+ global_page_state(NR_WRITEBACK) <= dirty_thresh) &&
+ (!do_memcg ||
+ (memcg_info.nr_unstable_nfs +
+ memcg_info.nr_writeback <= memcg_info.dirty_thresh)))
+ break;
congestion_wait(BLK_RW_ASYNC, HZ/10);
/*
diff --git a/mm/vmscan.c b/mm/vmscan.c
index fb0ae99..3c57788 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2068,7 +2068,7 @@ restart:
sc->nr_scanned - nr_scanned, sc))
goto restart;
- throttle_vm_writeout(sc->gfp_mask);
+ throttle_vm_writeout(sc->gfp_mask, sc->mem_cgroup);
}
/*
--
1.7.3.1
--
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