Re: [PATCH v5 06/12] migration/dirtyrate: Record hash results for each sampled page

[Dr. David Alan Gilbert]

* Chuan Zheng (zhengchuan@huawei.com) wrote:
> Record hash results for each sampled page, crc32 is taken to calculate
> hash results for each sampled 4K-page.
> 
> Signed-off-by: Chuan Zheng <zhengchuan@huawei.com>
> Signed-off-by: YanYing Zhuang <ann.zhuangyanying@huawei.com>
> ---
>  migration/dirtyrate.c | 136 
> ++++++++++++++++++++++++++++++++++++++++++++++++++
>  migration/dirtyrate.h |  15 ++++++
>  2 files changed, 151 insertions(+)
> 
> diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
> index f6a94d8..66de426 100644
> --- a/migration/dirtyrate.c
> +++ b/migration/dirtyrate.c
> @@ -10,6 +10,7 @@
>   * See the COPYING file in the top-level directory.
>   */
>  
> +#include <zlib.h>
>  #include "qemu/osdep.h"
>  #include "qapi/error.h"
>  #include "crypto/hash.h"
> @@ -66,6 +67,141 @@ static void update_dirtyrate(uint64_t msec)
>      DirtyStat.dirty_rate = dirtyrate;
>  }
>  
> +/*
> + * get hash result for the sampled memory with length of 4K byte in ramblock,
> + * which starts from ramblock base address.
> + */
> +static uint32_t get_ramblock_vfn_hash(struct RamblockDirtyInfo *info,
> +                                      uint64_t vfn)
> +{
> +    struct iovec iov_array;
> +    uint32_t crc;
> +
> +    iov_array.iov_base = info->ramblock_addr +
> +                         vfn * DIRTYRATE_SAMPLE_PAGE_SIZE;
> +    iov_array.iov_len = DIRTYRATE_SAMPLE_PAGE_SIZE;
> +
> +    crc = crc32(0, iov_array.iov_base, iov_array.iov_len);
> +
> +    return crc;
> +}
> +
> +static int save_ramblock_hash(struct RamblockDirtyInfo *info)
> +{
> +    unsigned int sample_pages_count;
> +    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(uint32_t));
> +    if (!info->hash_result) {
> +        ret = -1;
> +        goto out;
> +    }
> +
> +    info->sample_page_vfn = g_try_malloc0_n(sample_pages_count,
> +                                            sizeof(uint64_t));
> +    if (!info->sample_page_vfn) {
> +        g_free(info->hash_result);
> +        ret = -1;
> +        goto out;
> +    }
> +
> +    for (i = 0; i < sample_pages_count; i++) {
> +        info->sample_page_vfn[i] = g_rand_int_range(rand, 0,
> +                                                    info->ramblock_pages - 
> 1);
> +        info->hash_result[i] = get_ramblock_vfn_hash(info,
> +                                                     
> info->sample_page_vfn[i]);
> +    }
> +    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) >>
> +                                DIRTYRATE_PAGE_SHIFT_GB;
> +
> +    /* Right shift 12 bits to calc page count in 4KB */
> +    info->ramblock_pages = qemu_ram_get_used_length(block) >>
> +                           DIRTYRATE_PAGE_SHIFT_KB;
> +    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) {
> +        index = 0;
> +        block_dinfo = g_try_new(struct RamblockDirtyInfo, 1);
> +    } else {
> +        index++;
> +        block_dinfo = g_try_realloc(block_dinfo, (index + 1) *
> +                                    sizeof(struct RamblockDirtyInfo));
> +    }
> +    if (!block_dinfo) {
> +        return NULL;
> +    }
> +
> +    info = &block_dinfo[index];
> +    *block_index = index;
> +    memset(info, 0, sizeof(struct RamblockDirtyInfo));
> +
> +    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;
> +}
> +
>  static void calculate_dirtyrate(struct DirtyRateConfig config)
>  {
>      /* todo */
> diff --git a/migration/dirtyrate.h b/migration/dirtyrate.h
> index 8e25d93..e3adead 100644
> --- a/migration/dirtyrate.h
> +++ b/migration/dirtyrate.h
> @@ -24,6 +24,21 @@
>   */
>  #define RAMBLOCK_INFO_MAX_LEN                     256
>  
> +/*
> + * Sample page size 4K as default.
> + */
> +#define DIRTYRATE_SAMPLE_PAGE_SIZE                4096
> +
> +/*
> + * Sample page size 4K shift
> + */
> +#define DIRTYRATE_PAGE_SHIFT_KB                   12
> +
> +/*
> + * Sample page size 1G shift
> + */
> +#define DIRTYRATE_PAGE_SHIFT_GB                   30

Your naming is really odd here;  'PAGE_SHIFT_KB' divides
by 4KB, where as 'PAGE_SHIFT_GB' divices by 1KB.

Simplify this;  you can just do >>30 for GB because it's well known;
you don't need a #define constant for simple KB,MB,GB since
we all know them.

Also, I've asked before - do you really want 4KB explicitly - or
should you just use TARGET_PAGE_SIZE and TARGET_PAGE_BITS ?

Dave

> +
>  /* 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