percpu_counter: FBC_BATCH should be a variable
For NR_CPUS >= 16 values, FBC_BATCH is 2*NR_CPUS
Considering more and more distros are using high NR_CPUS values, it makes
sense to use a more sensible value for FBC_BATCH, and get rid of NR_CPUS.
A sensible value is 2*num_online_cpus(), with a minimum value of 32 (This
minimum value helps branch prediction in __percpu_counter_add())
We already have a hotcpu notifier, so we can adjust FBC_BATCH dynamically.
We rename FBC_BATCH to percpu_counter_batch since its not a constant
anymore.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index b0537c8..6c46c64 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1225,11 +1225,11 @@
} while (0)
#ifdef CONFIG_SMP
-/* Each CPU can accumulate FBC_BATCH blocks in their local
+/* Each CPU can accumulate percpu_counter_batch blocks in their local
* counters. So we need to make sure we have free blocks more
- * than FBC_BATCH * nr_cpu_ids. Also add a window of 4 times.
+ * than percpu_counter_batch * nr_cpu_ids. Also add a window of 4 times.
*/
-#define EXT4_FREEBLOCKS_WATERMARK (4 * (FBC_BATCH * nr_cpu_ids))
+#define EXT4_FREEBLOCKS_WATERMARK (4 * (percpu_counter_batch * nr_cpu_ids))
#else
#define EXT4_FREEBLOCKS_WATERMARK 0
#endif
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 6702a49..98d3fe7 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2498,7 +2498,7 @@
/*
* switch to non delalloc mode if we are running low
* on free block. The free block accounting via percpu
- * counters can get slightly wrong with FBC_BATCH getting
+ * counters can get slightly wrong with percpu_counter_batch getting
* accumulated on each CPU without updating global counters
* Delalloc need an accurate free block accounting. So switch
* to non delalloc when we are near to error range.