From 98f9ca0a3faa99b7388578d55eccecf272be4038 Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Wed, 28 May 2014 17:07:02 +0300 Subject: vhost: replace rcu with mutex All memory accesses are done under some VQ mutex. So lock/unlock all VQs is a faster equivalent of synchronize_rcu() for memory access changes. Some guests cause a lot of these changes, so it's helpful to make them faster. Reported-by: "Gonglei (Arei)" Signed-off-by: Michael S. Tsirkin --- drivers/vhost/vhost.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'drivers') diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 78987e4..1c05e60 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -593,6 +593,7 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m) { struct vhost_memory mem, *newmem, *oldmem; unsigned long size = offsetof(struct vhost_memory, regions); + int i; if (copy_from_user(&mem, m, size)) return -EFAULT; @@ -619,7 +620,14 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m) oldmem = rcu_dereference_protected(d->memory, lockdep_is_held(&d->mutex)); rcu_assign_pointer(d->memory, newmem); - synchronize_rcu(); + + /* All memory accesses are done under some VQ mutex. + * So below is a faster equivalent of synchronize_rcu() + */ + for (i = 0; i < d->nvqs; ++i) { + mutex_lock(&d->vqs[i]->mutex); + mutex_unlock(&d->vqs[i]->mutex); + } kfree(oldmem); return 0; } -- cgit v1.1