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Re: [PATCH v5 06/12] migration/dirtyrate: Record hash results for each s
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH v5 06/12] migration/dirtyrate: Record hash results for each sampled page |
Date: |
Thu, 27 Aug 2020 09:31:14 +0100 |
User-agent: |
Mutt/1.14.6 (2020-07-11) |
* Zheng Chuan (zhengchuan@huawei.com) wrote:
>
>
> 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.
TARGET_PAGE_SIZE is never 2M or 1G; it's always based on the smallest
MMU page on the platform; on x86 it's always 4kB; it's the unit that the
migration code works in when dealing with pages.
(use TARGET_PAGE_BITS to shift by).
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
[PATCH v5 02/12] migration/dirtyrate: add DirtyRateStatus to denote calculation status, Chuan Zheng, 2020/08/24
[PATCH v5 08/12] migration/dirtyrate: skip sampling ramblock with size below MIN_RAMBLOCK_SIZE, Chuan Zheng, 2020/08/24
[PATCH v5 10/12] migration/dirtyrate: Implement calculate_dirtyrate() function, 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 11/12] migration/dirtyrate: Implement qmp_cal_dirty_rate()/qmp_get_dirty_rate() function, 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 07/12] migration/dirtyrate: Compare page hash results for recorded sampled page, Chuan Zheng, 2020/08/24