mirror of
https://github.com/LadybirdBrowser/ladybird.git
synced 2024-08-17 09:20:28 +03:00
AK: Speed up BitmapView::find_next_range_of_unset_bits
While watching Andreas' most recent video, I noticed that this function only worked with 32 bit values, but was a serious performance bottleneck for the kernel. As such, I reworked it to use `size_t`, so it now can switch to 64-bit sweeps on 64-bit platforms. This caused test-js to go from 12.5 seconds hot to 11.5 seconds hot on my machine when running on KVM x86_64.
This commit is contained in:
parent
548529ace4
commit
e122502f70
Notes:
sideshowbarker
2024-07-17 22:38:26 +09:00
Author: https://github.com/Sylvyrfysh Commit: https://github.com/SerenityOS/serenity/commit/e122502f70f Pull-request: https://github.com/SerenityOS/serenity/pull/11223 Reviewed-by: https://github.com/BenWiederhake ✅ Reviewed-by: https://github.com/BertalanD
@ -7,8 +7,8 @@
|
||||
#pragma once
|
||||
|
||||
#include <AK/Array.h>
|
||||
#include <AK/BuiltinWrappers.h>
|
||||
#include <AK/Optional.h>
|
||||
#include <AK/Platform.h>
|
||||
#include <AK/StdLibExtras.h>
|
||||
#include <AK/Types.h>
|
||||
|
||||
@ -205,18 +205,20 @@ public:
|
||||
return {};
|
||||
}
|
||||
|
||||
u32* bitmap32 = (u32*)m_data;
|
||||
size_t bit_size = 8 * sizeof(size_t);
|
||||
|
||||
size_t* bitmap = (size_t*)m_data;
|
||||
|
||||
// Calculating the start offset.
|
||||
size_t start_bucket_index = from / 32;
|
||||
size_t start_bucket_bit = from % 32;
|
||||
size_t start_bucket_index = from / bit_size;
|
||||
size_t start_bucket_bit = from % bit_size;
|
||||
|
||||
size_t* start_of_free_chunks = &from;
|
||||
size_t free_chunks = 0;
|
||||
|
||||
for (size_t bucket_index = start_bucket_index; bucket_index < m_size / 32; ++bucket_index) {
|
||||
if (bitmap32[bucket_index] == 0xffffffff) {
|
||||
// Skip over completely full bucket of size 32.
|
||||
for (size_t bucket_index = start_bucket_index; bucket_index < m_size / bit_size; ++bucket_index) {
|
||||
if (bitmap[bucket_index] == NumericLimits<size_t>::max()) {
|
||||
// Skip over completely full bucket of size bit_size.
|
||||
if (free_chunks >= min_length) {
|
||||
return min(free_chunks, max_length);
|
||||
}
|
||||
@ -224,12 +226,12 @@ public:
|
||||
start_bucket_bit = 0;
|
||||
continue;
|
||||
}
|
||||
if (bitmap32[bucket_index] == 0x0) {
|
||||
// Skip over completely empty bucket of size 32.
|
||||
if (bitmap[bucket_index] == 0x0) {
|
||||
// Skip over completely empty bucket of size bit_size.
|
||||
if (free_chunks == 0) {
|
||||
*start_of_free_chunks = bucket_index * 32;
|
||||
*start_of_free_chunks = bucket_index * bit_size;
|
||||
}
|
||||
free_chunks += 32;
|
||||
free_chunks += bit_size;
|
||||
if (free_chunks >= max_length) {
|
||||
return max_length;
|
||||
}
|
||||
@ -237,26 +239,26 @@ public:
|
||||
continue;
|
||||
}
|
||||
|
||||
u32 bucket = bitmap32[bucket_index];
|
||||
size_t bucket = bitmap[bucket_index];
|
||||
u8 viewed_bits = start_bucket_bit;
|
||||
u32 trailing_zeroes = 0;
|
||||
|
||||
bucket >>= viewed_bits;
|
||||
start_bucket_bit = 0;
|
||||
|
||||
while (viewed_bits < 32) {
|
||||
while (viewed_bits < bit_size) {
|
||||
if (bucket == 0) {
|
||||
if (free_chunks == 0) {
|
||||
*start_of_free_chunks = bucket_index * 32 + viewed_bits;
|
||||
*start_of_free_chunks = bucket_index * bit_size + viewed_bits;
|
||||
}
|
||||
free_chunks += 32 - viewed_bits;
|
||||
viewed_bits = 32;
|
||||
free_chunks += bit_size - viewed_bits;
|
||||
viewed_bits = bit_size;
|
||||
} else {
|
||||
trailing_zeroes = count_trailing_zeroes_32(bucket);
|
||||
trailing_zeroes = count_trailing_zeroes(bucket);
|
||||
bucket >>= trailing_zeroes;
|
||||
|
||||
if (free_chunks == 0) {
|
||||
*start_of_free_chunks = bucket_index * 32 + viewed_bits;
|
||||
*start_of_free_chunks = bucket_index * bit_size + viewed_bits;
|
||||
}
|
||||
free_chunks += trailing_zeroes;
|
||||
viewed_bits += trailing_zeroes;
|
||||
@ -266,7 +268,7 @@ public:
|
||||
}
|
||||
|
||||
// Deleting trailing ones.
|
||||
u32 trailing_ones = count_trailing_zeroes_32(~bucket);
|
||||
u32 trailing_ones = count_trailing_zeroes(~bucket);
|
||||
bucket >>= trailing_ones;
|
||||
viewed_bits += trailing_ones;
|
||||
free_chunks = 0;
|
||||
@ -275,8 +277,8 @@ public:
|
||||
}
|
||||
|
||||
if (free_chunks < min_length) {
|
||||
size_t first_trailing_bit = (m_size / 32) * 32;
|
||||
size_t trailing_bits = size() % 32;
|
||||
size_t first_trailing_bit = (m_size / bit_size) * bit_size;
|
||||
size_t trailing_bits = size() % bit_size;
|
||||
for (size_t i = 0; i < trailing_bits; ++i) {
|
||||
if (!get(first_trailing_bit + i)) {
|
||||
if (free_chunks == 0)
|
||||
|
Loading…
Reference in New Issue
Block a user