Hello all,
during some performance diagnostics I stumbled on this slightly wasteful
code in pcnet_cs.c which I made the patch included at the bottom for
(two minor comment fixes included).
Tested using 2.6.11-ck3 (Linksys PCMCIA combo card), works.
The patch is against 2.6.11-ck3, but it applies cleanly to 2.6.12-rc1
and should almost certainly apply to anything else.
Improvement:
instead of *always* calculating
lea 0x2c0(%edx),%ebx
and then additionally doing the
mov %edx,0xc0(%ebx)
addition *if we need it*,
we now do the *whole* calculation of
mov %edx,0x380(%ebx)
*only* if we need it.
This even manages to save us a whole 16-byte alignment buffer loss
in this compilation case.
Result: slightly improves IRQ handler performance in both shared and
non-shared IRQ case, which should make my rusty P3/700 a slight bit happier.
Thank you for your support,
Andreas Mohr
old asm result (using gcc 3.3.5):
000015a0 <ei_irq_wrapper>:
15a0: 55 push %ebp
15a1: 89 e5 mov %esp,%ebp
15a3: 53 push %ebx
15a4: 8d 9a c0 02 00 00 lea 0x2c0(%edx),%ebx
15aa: e8 fc ff ff ff call 15ab <ei_irq_wrapper+0xb>
15af: 83 f8 01 cmp $0x1,%eax
15b2: 74 03 je 15b7 <ei_irq_wrapper+0x17>
15b4: 5b pop %ebx
15b5: 5d pop %ebp
15b6: c3 ret
15b7: 31 d2 xor %edx,%edx
15b9: 89 93 c0 00 00 00 mov %edx,0xc0(%ebx)
15bf: eb f3 jmp 15b4 <ei_irq_wrapper+0x14>
15c1: eb 0d jmp 15d0 <ei_watchdog>
15c3: 90 nop
15c4: 90 nop
15c5: 90 nop
15c6: 90 nop
15c7: 90 nop
15c8: 90 nop
15c9: 90 nop
15ca: 90 nop
15cb: 90 nop
15cc: 90 nop
15cd: 90 nop
15ce: 90 nop
15cf: 90 nop
000015d0 <ei_watchdog>:
new asm result:
000015a0 <ei_irq_wrapper>:
15a0: 55 push %ebp
15a1: 89 e5 mov %esp,%ebp
15a3: 53 push %ebx
15a4: 89 d3 mov %edx,%ebx
15a6: e8 fc ff ff ff call 15a7 <ei_irq_wrapper+0x7>
15ab: 83 f8 01 cmp $0x1,%eax
15ae: 74 03 je 15b3 <ei_irq_wrapper+0x13>
15b0: 5b pop %ebx
15b1: 5d pop %ebp
15b2: c3 ret
15b3: 31 d2 xor %edx,%edx
15b5: 89 93 80 03 00 00 mov %edx,0x380(%ebx)
15bb: eb f3 jmp 15b0 <ei_irq_wrapper+0x10>
15bd: 8d 76 00 lea 0x0(%esi),%esi
000015c0 <ei_watchdog>:
--- pcnet_cs.c 2005-03-28 11:33:11.000000000 +0200
+++ pcnet_cs.c.mod 2005-03-28 10:42:01.000000000 +0200
@@ -1155,11 +1155,13 @@
static irqreturn_t ei_irq_wrapper(int irq, void *dev_id, struct pt_regs *regs)
{
struct net_device *dev = dev_id;
- pcnet_dev_t *info = PRIV(dev);
+ pcnet_dev_t *info;
irqreturn_t ret = ei_interrupt(irq, dev_id, regs);
- if (ret == IRQ_HANDLED)
+ if (ret == IRQ_HANDLED) {
+ info = PRIV(dev);
info->stale = 0;
+ }
return ret;
}
@@ -1350,7 +1352,7 @@
if (count & 0x01)
buf[count-1] = inb(nic_base + PCNET_DATAPORT), xfer_count++;
- /* This was for the ALPHA version only, but enough people have
+ /* This was for the ALPHA version only, but enough people have been
encountering problems that it is still here. */
#ifdef PCMCIA_DEBUG
if (ei_debug > 4) { /* DMA termination address check... */
@@ -1424,7 +1426,7 @@
dma_start = jiffies;
#ifdef PCMCIA_DEBUG
- /* This was for the ALPHA version only, but enough people have
+ /* This was for the ALPHA version only, but enough people have been
encountering problems that it is still here. */
if (ei_debug > 4) { /* DMA termination address check... */
int addr, tries = 20;
-
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