On 11/20/2015 07:26 PM, Michael S. Tsirkin wrote:
On Fri, Nov 20, 2015 at 07:04:07PM +0800, Cao jin wrote:
On 11/20/2015 06:45 PM, Michael S. Tsirkin wrote:
On Fri, Nov 20, 2015 at 06:45:01PM +0800, Cao jin wrote:
2. As spec says, each capability must be DWORD aligned, so an optimization can
be done via Loop Unrolling.
Why do we want to optimize it?
For tiny performance improvement via less loop. take pcie express
capability(60 bytes at most) for example, it may loop 60 times, now we just
need 15 times, a quarter of before.
But who cares? This is not a data path operation.
It is tiny thing I found when browsing code. When found there are
several places looks like this, I think maybe it does good to qemu to do
this and CCed to you because it don`t look like a simple trivial patch.
So, hey Michael, if you don`t like this kind of optimization, that`t ok,
forget it. But I think it make me little confused when determine which
kind of patch should be CCed to you.
Signed-off-by: Cao jin <caoj.f...@cn.fujitsu.com>
---
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
.
--
Yours Sincerely,
Cao Jin
.
--
Yours Sincerely,
Cao Jin
