diff options
authorGilad Ben-Yossef <gilad@benyossef.com>2012-03-28 14:42:45 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-28 17:14:35 -0700
commit42be35d0390b966253136a285f507f5ad00fd9e8 (patch)
parentslub: only IPI CPUs that have per cpu obj to flush (diff)
fs: only send IPI to invalidate LRU BH when needed
In several code paths, such as when unmounting a file system (but not only) we send an IPI to ask each cpu to invalidate its local LRU BHs. For multi-cores systems that have many cpus that may not have any LRU BH because they are idle or because they have not performed any file system accesses since last invalidation (e.g. CPU crunching on high perfomance computing nodes that write results to shared memory or only using filesystems that do not use the bh layer.) This can lead to loss of performance each time someone switches the KVM (the virtual keyboard and screen type, not the hypervisor) if it has a USB storage stuck in. This patch attempts to only send an IPI to cpus that have LRU BH. Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 14 insertions, 1 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index 70e2017edd70..36d66653b931 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1384,10 +1384,23 @@ static void invalidate_bh_lru(void *arg)
+static bool has_bh_in_lru(int cpu, void *dummy)
+ struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
+ int i;
+ for (i = 0; i < BH_LRU_SIZE; i++) {
+ if (b->bhs[i])
+ return 1;
+ }
+ return 0;
void invalidate_bh_lrus(void)
- on_each_cpu(invalidate_bh_lru, NULL, 1);
+ on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);