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

[Zheng Chuan]

On 2020/8/26 20:35, Dr. David Alan Gilbert wrote:
> * 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.
> 
Hi, Dave.
Thank you for review.
OK, i will fix that in V6:)
> Also, I've asked before - do you really want 4KB explicitly - or
> should you just use TARGET_PAGE_SIZE and TARGET_PAGE_BITS ?
> 
> Dave
>
TARGET_PAGE_SIZE will be 2M or 1G for HugePage.
As you see, what we get is hash result of every 'virtual' 4K-page.
We care about if it is dirty within 4K length in ramblock, which would be more
accurate than TARGET_PAGE_SIZE which could be 2M or 1G.
On the other hand, the hugepage will be broken up into 4K during migration.

I think it is better we do hash at 'virtual' 4K-page granularity.

>> +
>>  /* Take 1s as default for calculation duration */
>>  #define DEFAULT_FETCH_DIRTYRATE_TIME_SEC          1
>>  
>> -- 
>> 1.8.3.1
>>