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[Qemu-devel] Re: [PATCH] qemu-kvm: Speed up of the dirty-bitmap-travelin
From: |
OHMURA Kei |
Subject: |
[Qemu-devel] Re: [PATCH] qemu-kvm: Speed up of the dirty-bitmap-traveling |
Date: |
Wed, 10 Feb 2010 18:55:49 +0900 |
User-agent: |
Thunderbird 2.0.0.23 (Windows/20090812) |
> Please reuse the changelog when reposing a patch, this makes it easier
> for me to apply it.
Thanks. Will follow it from next time.
> Should be a host long size, not guest. This will fail when running a
> 32-bit qemu-system-x86_64 binary.
Sorry. That was our mistake.
> Instead of using a nested loop if bitmap_ul[i] != 0, it is possible to
> use just a single loop (while (c> 0)), and process a long's worth of data.
>
> The only trickery is with big endian hosts, where the conversion from
> bit number to page number is a bit complicated.
To convert the bitmap from big endian to little endian, le_bswap macro in
bswap.h seems useful, which is now undefined. What do you think about this
approach?
This is an example bitmap-traveling code using le_bswap:
/*
* bitmap-traveling is faster than memory-traveling (for addr...)
* especially when most of the memory is not dirty.
*/
for (i = 0; i < len; i++) {
if (bitmap_ul[i] != 0) {
c = le_bswap(bitmap_ul[i], HOST_LONG_BITS);
while (c > 0) {
j = ffsl(c) - 1;
c &= ~(1ul << j);
page_number = i * HOST_LONG_BITS + j;
addr1 = page_number * TARGET_PAGE_SIZE;
addr = offset + addr1;
ram_addr = cpu_get_physical_page_desc(addr);
cpu_physical_memory_set_dirty(ram_addr);
}
}
}
[Qemu-devel] Re: [PATCH] qemu-kvm: Speed up of the dirty-bitmap-traveling, Avi Kivity, 2010/02/08