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Re: [Qemu-devel] [PATCH for 2.6 1/3] backup: Use Bitmap to replace "s->b
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH for 2.6 1/3] backup: Use Bitmap to replace "s->bitmap" |
Date: |
Mon, 23 Nov 2015 15:49:58 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 |
On 23/11/2015 10:55, Fam Zheng wrote:
>>> Why? I think bitmap_set is a better match with bitmap_new below.
>>
>> set_bit() is quicker than bitmap_set() if you only set one bit.
>
> How much quicker is it? This doesn't sound convincing enough for me to lose
> the
> readability.
Substantially. It's also documented:
/*
* Also the following operations apply to bitmaps.
*
* set_bit(bit, addr) *addr |= bit
* clear_bit(bit, addr) *addr &= ~bit
* change_bit(bit, addr) *addr ^= bit
* test_bit(bit, addr) Is bit set in *addr?
* test_and_set_bit(bit, addr) Set bit and return old value
* test_and_clear_bit(bit, addr) Clear bit and return old value
* test_and_change_bit(bit, addr) Change bit and return old value
* find_first_zero_bit(addr, nbits) Position first zero bit in *addr
* find_first_bit(addr, nbits) Position first set bit in *addr
* find_next_zero_bit(addr, nbits, bit) Position next zero bit in *addr >= bit
* find_next_bit(addr, nbits, bit) Position next set bit in *addr >= bit
*/
Paolo
Re: [Qemu-devel] [PATCH for 2.6 1/3] backup: Use Bitmap to replace "s->bitmap", John Snow, 2015/11/23
[Qemu-devel] [PATCH for 2.6 3/3] hbitmap: Drop "granularity", Fam Zheng, 2015/11/20
[Qemu-devel] [PATCH for 2.6 2/3] block: Hide HBitmap in block dirty bitmap interface, Fam Zheng, 2015/11/20