Re: [PATCH v3 05/10] migration/dirtyrate: Record hash results for each sampled page

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

* Chuan Zheng (zhengchuan@huawei.com) wrote:
> Record hash results for each sampled page.
> 
> Signed-off-by: Chuan Zheng <zhengchuan@huawei.com>
> Signed-off-by: YanYing Zhuang <ann.zhuangyanying@huawei.com>
> ---
>  migration/dirtyrate.c | 144 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  migration/dirtyrate.h |   7 +++
>  2 files changed, 151 insertions(+)
> 
> diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
> index c4304ef..62b6f69 100644
> --- a/migration/dirtyrate.c
> +++ b/migration/dirtyrate.c
> @@ -25,6 +25,7 @@
>  #include "dirtyrate.h"
>  
>  CalculatingDirtyRateState CalculatingState = CAL_DIRTY_RATE_INIT;
> +static unsigned long int qcrypto_hash_len = QCRYPTO_HASH_LEN;

Why do we need this static rather than just using the QCRYPTO_HASH_LEN ?
It's never going to change is it?
(and anyway it's just a MD5 len?)

>  static struct DirtyRateStat dirty_stat;
>  
>  static int dirty_rate_set_state(int new_state)
> @@ -71,6 +72,149 @@ static void update_dirtyrate(uint64_t msec)
>      dirty_stat.dirty_rate = dirty_rate;
>  }
>  
> +/*
> + * get hash result for the sampled memory with length of 4K byte in ramblock,
> + * which starts from ramblock base address.
> + */
> +static int get_ramblock_vfn_hash(struct RamblockDirtyInfo *info,
> +                                 unsigned long vfn, uint8_t **md)
> +{
> +    struct iovec iov_array;
> +    int ret = 0;
> +    int nkey = 1;
> +    size_t hash_len = qcrypto_hash_len;
> +
> +    iov_array.iov_base = info->ramblock_addr +
> +                         vfn * DIRTYRATE_SAMPLE_PAGE_SIZE;
> +    iov_array.iov_len = DIRTYRATE_SAMPLE_PAGE_SIZE;
> +
> +    if (qcrypto_hash_bytesv(QCRYPTO_HASH_ALG_MD5,
> +                            &iov_array, nkey,
> +                            md, &hash_len, NULL) < 0) {
> +        ret = -1;
> +    }
> +
> +    return ret;
> +}
> +
> +static int save_ramblock_hash(struct RamblockDirtyInfo *info)
> +{
> +    unsigned int sample_pages_count;
> +    uint8_t *md = NULL;
> +    int i;
> +    int ret = -1;
> +    GRand *rand = g_rand_new();
> +
> +    sample_pages_count = info->sample_pages_count;
> +
> +    /* ramblock size less than one page, return success to skip this ramblock */
> +    if (unlikely(info->ramblock_pages == 0 || sample_pages_count == 0)) {
> +        ret = 0;
> +        goto out;
> +    }
> +
> +    info->hash_result = g_try_malloc0_n(sample_pages_count,
> +                                        sizeof(uint8_t) * qcrypto_hash_len);
> +    if (!info->hash_result) {
> +        ret = -1;
> +        goto out;
> +    }
> +
> +    info->sample_page_vfn = g_try_malloc0_n(sample_pages_count,
> +                                            sizeof(unsigned long));
> +    if (!info->sample_page_vfn) {
> +        g_free(info->hash_result);
> +        ret = -1;
> +        goto out;
> +    }
> +
> +    for (i = 0; i < sample_pages_count; i++) {
> +        md = info->hash_result + i * qcrypto_hash_len;
> +        info->sample_page_vfn[i] = g_rand_int_range(rand, 0,
> +                                                    info->ramblock_pages - 1);
> +        ret = get_ramblock_vfn_hash(info, info->sample_page_vfn[i], &md);
> +        if (ret < 0) {
> +            goto out;
> +        }
> +    }
> +    ret = 0;
> +
> +out:
> +    g_rand_free(rand);
> +    return ret;
> +}
> +
> +static void get_ramblock_dirty_info(RAMBlock *block,
> +                                    struct RamblockDirtyInfo *info,
> +                                    struct DirtyRateConfig *config)
> +{
> +    uint64_t sample_pages_per_gigabytes = config->sample_pages_per_gigabytes;
> +
> +    /* Right shift 30 bits to calc block size in GB */
> +    info->sample_pages_count = (qemu_ram_get_used_length(block)
> +                                * sample_pages_per_gigabytes) >> 30;
> +
> +    /* Right shift 12 bits to calc page count in 4KB */
> +    info->ramblock_pages = qemu_ram_get_used_length(block) >> 12;

Is this really >> 12 ?  Should it actually be 
   / DIRTYRATE_SAMPLE_PAGE_SIZE ?

(and should you need that or just use TARGET_PAGE_SIZE?)

> +    info->ramblock_addr = qemu_ram_get_host_addr(block);
> +    strcpy(info->idstr, qemu_ram_get_idstr(block));
> +}
> +
> +static struct RamblockDirtyInfo *
> +alloc_ramblock_dirty_info(int *block_index,
> +                          struct RamblockDirtyInfo *block_dinfo)
> +{
> +    struct RamblockDirtyInfo *info = NULL;
> +    int index = *block_index;
> +
> +    if (!block_dinfo) {
> +        block_dinfo = g_try_new(struct RamblockDirtyInfo, 1);
> +        index = 0;
> +    } else {
> +        index++;
> +        block_dinfo = g_try_realloc(block_dinfo, (index + 1) *
> +                                    sizeof(struct RamblockDirtyInfo));
> +    }
> +    if (!block_dinfo) {
> +        return NULL;
> +    }
> +
> +    info = &block_dinfo[index];
> +    memset(info, 0, sizeof(struct RamblockDirtyInfo));
> +
> +    *block_index = index;
> +    return block_dinfo;
> +}
> +
> +static int record_ramblock_hash_info(struct RamblockDirtyInfo **block_dinfo,
> +                                     struct DirtyRateConfig config,
> +                                     int *block_index)
> +{
> +    struct RamblockDirtyInfo *info = NULL;
> +    struct RamblockDirtyInfo *dinfo = NULL;
> +    RAMBlock *block = NULL;
> +    int index = 0;
> +
> +    RAMBLOCK_FOREACH_MIGRATABLE(block) {
> +        dinfo = alloc_ramblock_dirty_info(&index, dinfo);
> +        if (dinfo == NULL) {
> +            return -1;
> +        }
> +        info = &dinfo[index];
> +        get_ramblock_dirty_info(block, info, &config);
> +        if (save_ramblock_hash(info) < 0) {
> +            *block_dinfo = dinfo;
> +            *block_index = index;
> +            return -1;
> +        }
> +    }
> +
> +    *block_dinfo = dinfo;
> +    *block_index = index;
> +
> +    return 0;

You should add some trace_ calls at various places to make this easier
to debug.

Dave

> +}
> +
>  static void calculate_dirtyrate(struct DirtyRateConfig config)
>  {
>      /* todo */
> diff --git a/migration/dirtyrate.h b/migration/dirtyrate.h
> index af57c80..0812b16 100644
> --- a/migration/dirtyrate.h
> +++ b/migration/dirtyrate.h
> @@ -20,10 +20,17 @@
>  #define DIRTYRATE_DEFAULT_SAMPLE_PAGES            256
>  
>  /*
> + * Sample page size 4K as default.
> + */
> +#define DIRTYRATE_SAMPLE_PAGE_SIZE                4096
> +
> +/*
>   * Record ramblock idstr
>   */
>  #define RAMBLOCK_INFO_MAX_LEN                     256
>  
> +#define QCRYPTO_HASH_LEN                          16
> +
>  /* 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