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Re: [PATCH v5 06/12] migration/dirtyrate: Record hash results for each s
From: |
Zheng Chuan |
Subject: |
Re: [PATCH v5 06/12] migration/dirtyrate: Record hash results for each sampled page |
Date: |
Thu, 27 Aug 2020 14:28:03 +0800 |
User-agent: |
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 |
On 2020/8/26 20:30, Dr. David Alan Gilbert wrote:
> * David Edmondson (dme@dme.org) wrote:
>> On Monday, 2020-08-24 at 17:14:34 +08, Chuan Zheng 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;
>>
>> There's no need for an iovec now that crc32() is being used.
>>
OK, will take two variables instead to represent base address and length.
>>> + 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;
>>
>> There's no need to initialise "ret".
>>
>>> + GRand *rand = g_rand_new();
>>
>> Calling g_rand_new() when the result may not be used (because of the
>> various conditions immediately below) seems as though it might waste
>> entropy. Could this be pushed down just above the loop? It would even
>> get rid of the gotos ;-)
>>
OK, i'll try it.
>>> + 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;
>>
>> Doing the calculation this way around seems odd. Why was it not:
>>
>> info->sample_pages_count = (qemu_ram_get_used_length(block) >>
>> DIRTYRATE_PAGE_SHIFT_GB) *
>> sample_pages_per_gigabytes;
>>
>> ?
>
> Because that would give 0 for a 0.5GB block
>
> Dave
>
>>> +
>>> + /* 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));
>>
>> g_try_renew() instead of g_try_realloc()?
>>
Hi,
I am not sure that because there only one place in qemu to use g_try_renew.
Could you tell me why, because i think g_try_realloc will also return NULL when
error happen:)
>>> + }
>>> + 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;
>>
>> There's no need to initialise "info" or "block".
>>
OK, will remove unused initialization in V6.
>> The declaration of "info" could be pushed into the loop.
>>
>>> + 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 9db269d..5050add 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
>>> +
>>> /* Take 1s as default for calculation duration */
>>> #define DEFAULT_FETCH_DIRTYRATE_TIME_SEC 1
>>>
>>> --
>>> 1.8.3.1
>>
>> dme.
>> --
>> You bring light in.
>>
- [PATCH v5 11/12] migration/dirtyrate: Implement qmp_cal_dirty_rate()/qmp_get_dirty_rate() function, (continued)
- [PATCH v5 11/12] migration/dirtyrate: Implement qmp_cal_dirty_rate()/qmp_get_dirty_rate() function, Chuan Zheng, 2020/08/24
- [PATCH v5 02/12] migration/dirtyrate: add DirtyRateStatus to denote calculation status, Chuan Zheng, 2020/08/24
- [PATCH v5 05/12] migration/dirtyrate: move RAMBLOCK_FOREACH_MIGRATABLE into ram.h, Chuan Zheng, 2020/08/24
- [PATCH v5 01/12] migration/dirtyrate: setup up query-dirtyrate framwork, Chuan Zheng, 2020/08/24
- [PATCH v5 06/12] migration/dirtyrate: Record hash results for each sampled page, Chuan Zheng, 2020/08/24
[PATCH v5 07/12] migration/dirtyrate: Compare page hash results for recorded sampled page, Chuan Zheng, 2020/08/24
[PATCH v5 09/12] migration/dirtyrate: Implement get_sample_page_period() and block_sample_page_period(), Chuan Zheng, 2020/08/24
[PATCH v5 12/12] migration/dirtyrate: Add trace_calls to make it easier to debug, Chuan Zheng, 2020/08/24
[PATCH v5 10/12] migration/dirtyrate: Implement calculate_dirtyrate() function, Chuan Zheng, 2020/08/24