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[Qemu-devel] [PATCH] PCI: minor performance optimization
From: |
Cao jin |
Subject: |
[Qemu-devel] [PATCH] PCI: minor performance optimization |
Date: |
Fri, 20 Nov 2015 18:45:01 +0800 |
1. Do param check in pci_add_capability2(), as it is a public API.
2. As spec says, each capability must be DWORD aligned, so an optimization can
be done via Loop Unrolling.
Signed-off-by: Cao jin <address@hidden>
---
hw/pci/pci.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 168b9cc..1e99603 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -1924,13 +1924,15 @@ PCIDevice *pci_create_simple(PCIBus *bus, int devfn,
const char *name)
static uint8_t pci_find_space(PCIDevice *pdev, uint8_t size)
{
int offset = PCI_CONFIG_HEADER_SIZE;
- int i;
- for (i = PCI_CONFIG_HEADER_SIZE; i < PCI_CONFIG_SPACE_SIZE; ++i) {
+ int i = PCI_CONFIG_HEADER_SIZE;;
+
+ for (; i < PCI_CONFIG_SPACE_SIZE; i = i + 4) {
if (pdev->used[i])
- offset = i + 1;
- else if (i - offset + 1 == size)
+ offset = i + 4;
+ else if (i - offset >= size)
return offset;
}
+
return 0;
}
@@ -2144,6 +2146,8 @@ int pci_add_capability2(PCIDevice *pdev, uint8_t cap_id,
uint8_t *config;
int i, overlapping_cap;
+ assert(size > 0);
+
if (!offset) {
offset = pci_find_space(pdev, size);
if (!offset) {
--
2.1.0
- [Qemu-devel] [PATCH] PCI: minor performance optimization,
Cao jin <=