Re: [PATCH v5 08/12] migration/dirtyrate: skip sampling ramblock with size below MIN_RAMBLOCK_SIZE

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Chuan Zheng (zhengchuan@huawei.com) wrote:
> In order to sample real RAM, skip ramblock with size below MIN_RAMBLOCK_SIZE
> which is set as 128M.
> 
> Signed-off-by: Chuan Zheng <zhengchuan@huawei.com>
> ---
>  migration/dirtyrate.c | 24 ++++++++++++++++++++++++
>  migration/dirtyrate.h | 10 ++++++++++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
> index 050270d..bd398b7 100644
> --- a/migration/dirtyrate.c
> +++ b/migration/dirtyrate.c
> @@ -173,6 +173,24 @@ alloc_ramblock_dirty_info(int *block_index,
>      return block_dinfo;
>  }
>  
> +static int skip_sample_ramblock(RAMBlock *block)
> +{
> +    int64_t ramblock_size;
> +
> +    /* ramblock size in MB */
> +    ramblock_size = qemu_ram_get_used_length(block) >> DIRTYRATE_PAGE_SHIFT_MB;
> +
> +    /*
> +     * Consider ramblock with size larger than 128M is what we
> +     * want to sample.
> +     */
> +    if (ramblock_size < MIN_RAMBLOCK_SIZE) {
> +        return -1;
> +    }

This seems way too complicated for:

  if (qemu_ram_get_used_length(block) < (MIN_RAMBLOCK_SIZE << 10)) {
      return -1;
  }

  return 0;

(even easier if it just returned bool from the comparison)

Dave

> +    return 0;
> +}
> +
>  static int record_ramblock_hash_info(struct RamblockDirtyInfo **block_dinfo,
>                                       struct DirtyRateConfig config,
>                                       int *block_index)
> @@ -183,6 +201,9 @@ static int record_ramblock_hash_info(struct RamblockDirtyInfo **block_dinfo,
>      int index = 0;
>  
>      RAMBLOCK_FOREACH_MIGRATABLE(block) {
> +        if (skip_sample_ramblock(block) < 0) {
> +            continue;
> +        }
>          dinfo = alloc_ramblock_dirty_info(&index, dinfo);
>          if (dinfo == NULL) {
>              return -1;
> @@ -249,6 +270,9 @@ static int compare_page_hash_info(struct RamblockDirtyInfo *info,
>      RAMBlock *block = NULL;
>  
>      RAMBLOCK_FOREACH_MIGRATABLE(block) {
> +        if (skip_sample_ramblock(block) < 0) {
> +            continue;
> +        }
>          block_dinfo = NULL;
>          if (!find_page_matched(block, info, block_index + 1, &block_dinfo)) {
>              continue;
> diff --git a/migration/dirtyrate.h b/migration/dirtyrate.h
> index e3adead..600bceb 100644
> --- a/migration/dirtyrate.h
> +++ b/migration/dirtyrate.h
> @@ -35,10 +35,20 @@
>  #define DIRTYRATE_PAGE_SHIFT_KB                   12
>  
>  /*
> + * Sample page size MB shift
> + */
> +#define DIRTYRATE_PAGE_SHIFT_MB                   20
> +
> +/*
>   * Sample page size 1G shift
>   */
>  #define DIRTYRATE_PAGE_SHIFT_GB                   30
>  
> +/*
> + * minimum ramblock size to sampled
> + */
> +#define MIN_RAMBLOCK_SIZE                         128
> +
>  /* Take 1s as default for calculation duration */
>  #define DEFAULT_FETCH_DIRTYRATE_TIME_SEC          1
>  
> -- 
> 1.8.3.1
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK