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Re: [Qemu-devel] [RFC] find_next_bit optimizations
From: |
Peter Lieven |
Subject: |
Re: [Qemu-devel] [RFC] find_next_bit optimizations |
Date: |
Mon, 11 Mar 2013 16:24:07 +0100 |
> How would that be different in your patch? But you can solve it by
> making two >= loops, one checking for 4*BITS_PER_LONG and one checking
> BITS_PER_LONG.
This is what I have now:
diff --git a/util/bitops.c b/util/bitops.c
index e72237a..b0dc93f 100644
--- a/util/bitops.c
+++ b/util/bitops.c
@@ -24,12 +24,13 @@ unsigned long find_next_bit(const unsigned long *addr,
unsigned long size,
const unsigned long *p = addr + BITOP_WORD(offset);
unsigned long result = offset & ~(BITS_PER_LONG-1);
unsigned long tmp;
+ unsigned long d0,d1,d2,d3;
if (offset >= size) {
return size;
}
size -= result;
- offset %= BITS_PER_LONG;
+ offset &= (BITS_PER_LONG-1);
if (offset) {
tmp = *(p++);
tmp &= (~0UL << offset);
@@ -42,7 +43,19 @@ unsigned long find_next_bit(const unsigned long *addr,
unsigned long size,
size -= BITS_PER_LONG;
result += BITS_PER_LONG;
}
- while (size & ~(BITS_PER_LONG-1)) {
+ while (size >= 4*BITS_PER_LONG) {
+ d0 = *p;
+ d1 = *(p+1);
+ d2 = *(p+2);
+ d3 = *(p+3);
+ if (d0 || d1 || d2 || d3) {
+ break;
+ }
+ p+=4;
+ result += 4*BITS_PER_LONG;
+ size -= 4*BITS_PER_LONG;
+ }
+ while (size >= BITS_PER_LONG) {
if ((tmp = *(p++))) {
goto found_middle;
}
- [Qemu-devel] [RFC] find_next_bit optimizations, Peter Lieven, 2013/03/11
- Re: [Qemu-devel] [RFC] find_next_bit optimizations, Peter Maydell, 2013/03/11
- Re: [Qemu-devel] [RFC] find_next_bit optimizations, Paolo Bonzini, 2013/03/11
- Re: [Qemu-devel] [RFC] find_next_bit optimizations, Peter Lieven, 2013/03/11
- Re: [Qemu-devel] [RFC] find_next_bit optimizations, Peter Lieven, 2013/03/11
- Re: [Qemu-devel] [RFC] find_next_bit optimizations, Paolo Bonzini, 2013/03/11
- Re: [Qemu-devel] [RFC] find_next_bit optimizations,
Peter Lieven <=
- Re: [Qemu-devel] [RFC] find_next_bit optimizations, Paolo Bonzini, 2013/03/11
- Re: [Qemu-devel] [RFC] find_next_bit optimizations, Peter Lieven, 2013/03/11
- Re: [Qemu-devel] [RFC] find_next_bit optimizations, Paolo Bonzini, 2013/03/11
- Re: [Qemu-devel] [RFC] find_next_bit optimizations, ronnie sahlberg, 2013/03/11
- Re: [Qemu-devel] [RFC] find_next_bit optimizations, Paolo Bonzini, 2013/03/11
- Re: [Qemu-devel] [RFC] find_next_bit optimizations, Peter Lieven, 2013/03/11
- [Qemu-devel] [PATCH] bitops: unroll while loop in find_next_bit()., Peter Lieven, 2013/03/12
- Re: [Qemu-devel] [RFC] find_next_bit optimizations, Peter Maydell, 2013/03/11
- Re: [Qemu-devel] [RFC] find_next_bit optimizations, Peter Maydell, 2013/03/11
- Re: [Qemu-devel] [RFC] find_next_bit optimizations, Peter Lieven, 2013/03/11