linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
* [PATCH] KVM: PPC: BOOK3S: book3s_hv_nested.c: improve branch prediction for k.alloc
@ 2023-04-07  9:31 Kautuk Consul
  2023-04-07 13:46 ` Bagas Sanjaya
  0 siblings, 1 reply; 8+ messages in thread
From: Kautuk Consul @ 2023-04-07  9:31 UTC (permalink / raw)
  To: Michael Ellerman, Nicholas Piggin, Christophe Leroy,
	Fabiano Rosas, Paolo Bonzini, Chao Peng, Sean Christopherson
  Cc: linuxppc-dev, linux-kernel, Kautuk Consul

I used the unlikely() macro on the return values of the k.alloc
calls and found that it changes the code generation a bit.
Optimize all return paths of k.alloc calls by improving
branch prediction on return value of k.alloc.

Signed-off-by: Kautuk Consul <kconsul@linux.vnet.ibm.com>
---
 arch/powerpc/kvm/book3s_hv_nested.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
index 5a64a1341e6f..dbf2dd073e1f 100644
--- a/arch/powerpc/kvm/book3s_hv_nested.c
+++ b/arch/powerpc/kvm/book3s_hv_nested.c
@@ -446,7 +446,7 @@ long kvmhv_nested_init(void)
 		ptb_order = 12;
 	pseries_partition_tb = kmalloc(sizeof(struct patb_entry) << ptb_order,
 				       GFP_KERNEL);
-	if (!pseries_partition_tb) {
+	if (unlikely(!pseries_partition_tb)) {
 		pr_err("kvm-hv: failed to allocated nested partition table\n");
 		return -ENOMEM;
 	}
@@ -575,7 +575,7 @@ long kvmhv_copy_tofrom_guest_nested(struct kvm_vcpu *vcpu)
 		return H_PARAMETER;
 
 	buf = kzalloc(n, GFP_KERNEL | __GFP_NOWARN);
-	if (!buf)
+	if (unlikely(!buf))
 		return H_NO_MEM;
 
 	gp = kvmhv_get_nested(vcpu->kvm, l1_lpid, false);
@@ -689,7 +689,7 @@ static struct kvm_nested_guest *kvmhv_alloc_nested(struct kvm *kvm, unsigned int
 	long shadow_lpid;
 
 	gp = kzalloc(sizeof(*gp), GFP_KERNEL);
-	if (!gp)
+	if (unlikely(!gp))
 		return NULL;
 	gp->l1_host = kvm;
 	gp->l1_lpid = lpid;
@@ -1633,7 +1633,7 @@ static long int __kvmhv_nested_page_fault(struct kvm_vcpu *vcpu,
 	/* 4. Insert the pte into our shadow_pgtable */
 
 	n_rmap = kzalloc(sizeof(*n_rmap), GFP_KERNEL);
-	if (!n_rmap)
+	if (unlikely(!n_rmap))
 		return RESUME_GUEST; /* Let the guest try again */
 	n_rmap->rmap = (n_gpa & RMAP_NESTED_GPA_MASK) |
 		(((unsigned long) gp->l1_lpid) << RMAP_NESTED_LPID_SHIFT);
-- 
2.39.2


^ permalink raw reply related	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2023-04-19 10:09 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-04-07  9:31 [PATCH] KVM: PPC: BOOK3S: book3s_hv_nested.c: improve branch prediction for k.alloc Kautuk Consul
2023-04-07 13:46 ` Bagas Sanjaya
2023-04-07 16:01   ` Sean Christopherson
2023-04-11  4:59     ` Kautuk Consul
2023-04-11  6:35       ` Michael Ellerman
     [not found]         ` <CAKWYkK0hjMiP7yJWWjWX8CqS1Lcqi2z4P1bzj14-AU8SzBkYqw@mail.gmail.com>
2023-04-11  9:04           ` Kautuk Consul
2023-04-12  7:04         ` Kautuk Consul
2023-04-19 10:08           ` Kautuk Consul

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).