OHMURA Kei wrote:
> dirty-bitmap-traveling is carried out by byte size in qemu-kvm.c.
> But We think that dirty-bitmap-traveling by long size is faster than by byte
> size especially when most of memory is not dirty.
Sounds logical - do you have numbers on the improvement?
Would be great if you could provide a version for upstream as well
because it will likely replace this qemu-kvm code on day.
Jan
>
> Signed-off-by: OHMURA Kei <ohmura.kei@xxxxxxxxxxxxx>
> ---
> qemu-kvm.c | 49 ++++++++++++++++++++++++++++++++++++++++++-------
> 1 files changed, 42 insertions(+), 7 deletions(-)
>
> diff --git a/qemu-kvm.c b/qemu-kvm.c
> index a305907..5459cdd 100644
> --- a/qemu-kvm.c
> +++ b/qemu-kvm.c
> @@ -2433,22 +2433,21 @@ int kvm_physical_memory_set_dirty_tracking(int enable)
> }
>
> /* get kvm's dirty pages bitmap and update qemu's */
> -static int kvm_get_dirty_pages_log_range(unsigned long start_addr,
> - unsigned char *bitmap,
> - unsigned long offset,
> - unsigned long mem_size)
> +static void kvm_get_dirty_pages_log_range_by_byte(unsigned int start,
> + unsigned int end,
> + unsigned char *bitmap,
> + unsigned long offset)
> {
> unsigned int i, j, n = 0;
> unsigned char c;
> unsigned long page_number, addr, addr1;
> ram_addr_t ram_addr;
> - unsigned int len = ((mem_size / TARGET_PAGE_SIZE) + 7) / 8;
>
> /*
> * bitmap-traveling is faster than memory-traveling (for addr...)
> * especially when most of the memory is not dirty.
> */
> - for (i = 0; i < len; i++) {
> + for (i = start; i < end; i++) {
> c = bitmap[i];
> while (c > 0) {
> j = ffsl(c) - 1;
> @@ -2461,13 +2460,49 @@ static int kvm_get_dirty_pages_log_range(unsigned long start_addr,
> n++;
> }
> }
> +}
> +
> +static int kvm_get_dirty_pages_log_range_by_long(unsigned long start_addr,
> + unsigned char *bitmap,
> + unsigned long offset,
> + unsigned long mem_size)
> +{
> + unsigned int i;
> + unsigned int len;
> + unsigned long *bitmap_ul = (unsigned long *)bitmap;
> +
> + /* bitmap-traveling by long size is faster than by byte size
> + * especially when most of memory is not dirty.
> + * bitmap should be long-size aligned for traveling by long.
> + */
> + if (((unsigned long)bitmap & (TARGET_LONG_SIZE - 1)) == 0) {
> + len = ((mem_size / TARGET_PAGE_SIZE) + TARGET_LONG_BITS - 1) /
> + TARGET_LONG_BITS;
> + for (i = 0; i < len; i++)
> + if (bitmap_ul[i] != 0)
> + kvm_get_dirty_pages_log_range_by_byte(i * TARGET_LONG_SIZE,
> + (i + 1) * TARGET_LONG_SIZE, bitmap, offset);
> + /*
> + * We will check the remaining dirty-bitmap,
> + * when the mem_size is not a multiple of TARGET_LONG_SIZE.
> + */
> + if ((mem_size & (TARGET_LONG_SIZE - 1)) != 0) {
> + len = ((mem_size / TARGET_PAGE_SIZE) + 7) / 8;
> + kvm_get_dirty_pages_log_range_by_byte(i * TARGET_LONG_SIZE,
> + len, bitmap, offset);
> + }
> + } else { /* slow path: traveling by byte. */
> + len = ((mem_size / TARGET_PAGE_SIZE) + 7) / 8;
> + kvm_get_dirty_pages_log_range_by_byte(0, len, bitmap, offset);
> + }
> +
> return 0;
> }
>
> static int kvm_get_dirty_bitmap_cb(unsigned long start, unsigned long len,
> void *bitmap, void *opaque)
> {
> - return kvm_get_dirty_pages_log_range(start, bitmap, start, len);
> + return kvm_get_dirty_pages_log_range_by_long(start, bitmap, start, len);
> }
>
> /*
> -- 1.6.3.3
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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