Re: [PATCH 05/13] migration/postcopy: Drop PostcopyBlocktimeContext.start_time

[Fabiano Rosas <farosas@suse.de>]

Peter Xu <peterx@redhat.com> writes:

> Now with 64bits, the offseting using start_time is not needed anymore,
> because the array can always remember the whole timestamp.
>
> Then drop the unused parameter in get_low_time_offset() altogether.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  migration/postcopy-ram.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index 72f9075e69..c6ae4b650c 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -123,7 +123,6 @@ typedef struct PostcopyBlocktimeContext {
>      uint64_t last_begin;
>      /* number of vCPU are suspended */
>      int smp_cpus_down;
> -    uint64_t start_time;
>  
>      /*
>       * Handler for exit event, necessary for
> @@ -157,7 +156,6 @@ static struct PostcopyBlocktimeContext *blocktime_context_new(void)
>      ctx->vcpu_blocktime_total = g_new0(uint64_t, smp_cpus);
>      ctx->vcpu_addr = g_new0(uintptr_t, smp_cpus);
>      ctx->exit_notifier.notify = migration_exit_cb;
> -    ctx->start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
>      qemu_add_exit_notifier(&ctx->exit_notifier);
>  
>      return ctx;
> @@ -818,9 +816,9 @@ static int get_mem_fault_cpu_index(uint32_t pid)
>      return -1;
>  }
>  
> -static uint64_t get_low_time_offset(PostcopyBlocktimeContext *dc)
> +static uint64_t get_low_time_offset(void)
>  {
> -    return (uint64_t)qemu_clock_get_ms(QEMU_CLOCK_REALTIME) - dc->start_time;
> +    return (uint64_t)qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
>  }

Looking at this and the previous patch, this not "low" anymore, i.e.,
not the lower 32 bits of a 64 bit value. This function and related
variables should be renamed.

>  
>  /*
> @@ -847,7 +845,7 @@ void mark_postcopy_blocktime_begin(uintptr_t addr, uint32_t ptid,
>          return;
>      }
>  
> -    low_time_offset = get_low_time_offset(dc);
> +    low_time_offset = get_low_time_offset();
>      if (dc->vcpu_addr[cpu] == 0) {
>          dc->smp_cpus_down++;
>      }
> @@ -907,7 +905,7 @@ static void mark_postcopy_blocktime_end(uintptr_t addr)
>          return;
>      }
>  
> -    low_time_offset = get_low_time_offset(dc);
> +    low_time_offset = get_low_time_offset();
>      /* lookup cpu, to clear it,
>       * that algorithm looks straightforward, but it's not
>       * optimal, more optimal algorithm is keeping tree or hash