Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1587532

[PATCH 5/5] mm: add debugfs interface for parallel free tuning

Show all headers | View raw

Make it possible to set different values for async_free_threshold and
max_gather_batch_count through debugfs.

With this, we can do tests for different purposes:
1 Restore vanilla kernel bahaviour for performance comparison.
  Set max_gather_batch_count to a value like 20 to effectively restore
  the behaviour of vanilla kernel since this will make page gathered
  always smaller than async_free_threshold(effectively disable parallel
  free);
2 Debug purpose.
  Set async_free_threshold to a very small value(like 128) to trigger
  parallel free even on ordinary processes, ideal for debug purpose with
  a virtual machine that doesn't have much memory assigned to it;
3 Performance tuning.
  Use a different value for async_free_threshold and max_gather_batch_count
  other than the default to test if parallel free performs better or worse.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
---
 mm/memory.c | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 7d1fe74084be..9ca07c59e525 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -184,6 +184,35 @@ static void check_sync_rss_stat(struct task_struct *task)
 
 #ifdef HAVE_GENERIC_MMU_GATHER
 
+static unsigned long async_free_threshold = ASYNC_FREE_THRESHOLD;
+static unsigned long max_gather_batch_count = MAX_GATHER_BATCH_COUNT;
+
+#ifdef CONFIG_DEBUG_FS
+static int __init tlb_mmu_parallel_free_debugfs(void)
+{
+	umode_t mode = S_IFREG | S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
+	struct dentry *dir;
+
+	dir = debugfs_create_dir("parallel_free", NULL);
+	if (!dir)
+		return -ENOMEM;
+
+	if (!debugfs_create_ulong("async_free_threshold", mode, dir,
+				&async_free_threshold))
+		goto fail;
+	if (!debugfs_create_ulong("max_gather_batch_count", mode, dir,
+				&max_gather_batch_count))
+		goto fail;
+
+	return 0;
+
+fail:
+	debugfs_remove_recursive(dir);
+	return -ENOMEM;
+}
+late_initcall(tlb_mmu_parallel_free_debugfs);
+#endif
+
 static bool tlb_next_batch(struct mmu_gather *tlb)
 {
 	struct mmu_gather_batch *batch;
@@ -194,7 +223,7 @@ static bool tlb_next_batch(struct mmu_gather *tlb)
 		return true;
 	}
 
-	if (tlb->batch_count == MAX_GATHER_BATCH_COUNT)
+	if (tlb->batch_count == max_gather_batch_count)
 		return false;
 
 	batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
@@ -306,7 +335,7 @@ static void tlb_flush_mmu_free(struct mmu_gather *tlb)
 {
 	struct batch_free_struct *batch_free = NULL;
 
-	if (tlb->page_nr >= ASYNC_FREE_THRESHOLD)
+	if (tlb->page_nr >= async_free_threshold)
 		batch_free = kmalloc(sizeof(*batch_free), GFP_NOWAIT | __GFP_NOWARN);
 
 	if (batch_free) {
-- 
2.9.3

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH 0/5] mm: support parallel free of memory Aaron Lu <aaron.lu@intel.com> - 2017-02-24 12:50 +0100
  [PATCH 5/5] mm: add debugfs interface for parallel free tuning Aaron Lu <aaron.lu@intel.com> - 2017-02-24 12:50 +0100
  [PATCH 1/5] mm: add tlb_flush_mmu_free_batches Aaron Lu <aaron.lu@intel.com> - 2017-02-24 12:50 +0100
  [PATCH 2/5] mm: parallel free pages Aaron Lu <aaron.lu@intel.com> - 2017-02-24 12:50 +0100
  [PATCH 3/5] mm: use a dedicated workqueue for the free workers Aaron Lu <aaron.lu@intel.com> - 2017-02-24 12:50 +0100
  Re: [PATCH 0/5] mm: support parallel free of memory Dave Hansen <dave.hansen@intel.com> - 2017-03-01 01:50 +0100
    Re: [PATCH 0/5] mm: support parallel free of memory Aaron Lu <aaron.lu@intel.com> - 2017-03-01 02:30 +0100
  Re: [PATCH 0/5] mm: support parallel free of memory Andrew Morton <akpm@linux-foundation.org> - 2017-03-01 03:40 +0100

csiph-web