* Wei Yang (richardw.y...@linux.intel.com) wrote:
> The purpose of the calculation is to find a HostPage which is partially
> dirty.
>
> * fixup_start_addr points to the start of the HostPage to discard
> * run_start points to the next HostPage to check
>
> While in the middle stage, there would two cases for run_start:
>
> * aligned with HostPage means this is not partially dirty
> * not aligned means this is partially dirty
>
> When it is aligned, no work and calculation is necessary. run_start
> already points to the start of next HostPage and is ready to continue.
>
> When it is not aligned, the calculation could be simplified with:
>
> * fixup_start_addr = QEMU_ALIGN_DOWN(run_start, host_ratio)
> * run_start = QEMU_ALIGN_UP(run_start, host_ratio)
>
> By doing so, run_start always points to the next HostPage to check.
> fixup_start_addr always points to the HostPage to discard.
>
> Signed-off-by: Wei Yang <richardw.y...@linux.intel.com>
Yes that's a lot shorter; note it doess it on top of your cleanup
from a couple of weeks back.
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
> migration/ram.c | 34 +++++++---------------------------
> 1 file changed, 7 insertions(+), 27 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index c9585487ac..d86661a015 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -2956,7 +2956,6 @@ static void
> postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass,
> }
>
> while (run_start < pages) {
> - unsigned long fixup_start_addr;
> unsigned long host_offset;
>
> /*
> @@ -2964,45 +2963,26 @@ static void
> postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass,
> * page, then we need to fixup this host page.
> */
> host_offset = run_start % host_ratio;
> - if (host_offset) {
> - fixup_start_addr = run_start - host_offset;
> - /*
> - * This host page has gone, the next loop iteration starts
> - * from after the fixup
> - */
> - run_start = fixup_start_addr + host_ratio;
> - } else {
> + if (!host_offset) {
> /* Find the end of this run */
> - unsigned long run_end;
> if (unsent_pass) {
> - run_end = find_next_bit(unsentmap, pages, run_start + 1);
> + run_start = find_next_bit(unsentmap, pages, run_start + 1);
> } else {
> - run_end = find_next_zero_bit(bitmap, pages, run_start + 1);
> + run_start = find_next_zero_bit(bitmap, pages, run_start + 1);
> }
> /*
> * If the end isn't at the start of a host page, then the
> * run doesn't finish at the end of a host page
> * and we need to discard.
> */
> - host_offset = run_end % host_ratio;
> - if (host_offset) {
> - fixup_start_addr = run_end - host_offset;
> - /*
> - * This host page has gone, the next loop iteration starts
> - * from after the fixup
> - */
> - run_start = fixup_start_addr + host_ratio;
> - } else {
> - /*
> - * No discards on this iteration, next loop starts from
> - * next sent/dirty page
> - */
> - run_start = run_end + 1;
> - }
> + host_offset = run_start % host_ratio;
> }
>
> if (host_offset) {
> unsigned long page;
> + unsigned long fixup_start_addr = QEMU_ALIGN_DOWN(run_start,
> + host_ratio);
> + run_start = QEMU_ALIGN_UP(run_start, host_ratio);
>
> /* Tell the destination to discard this page */
> if (unsent_pass || !test_bit(fixup_start_addr, unsentmap)) {
> --
> 2.17.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
