Re: [RFC PATCH 1/8] migration/dirtyrate: Add get_dirtyrate_thread() function

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

* Chuan Zheng (zhengchuan@huawei.com) wrote:
> From: Zheng Chuan <zhengchuan@huawei.com>
> 
> Add get_dirtyrate_thread() functions
> 
> Signed-off-by: Zheng Chuan <zhengchuan@huawei.com>
> Signed-off-by: YanYing Zhang <ann.zhuangyanying@huawei.com>
> ---
>  migration/dirtyrate.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  migration/dirtyrate.h | 38 +++++++++++++++++++++++++++++++
>  2 files changed, 101 insertions(+)
>  create mode 100644 migration/dirtyrate.c
>  create mode 100644 migration/dirtyrate.h
> 
> diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
> new file mode 100644
> index 0000000..fc652fb
> --- /dev/null
> +++ b/migration/dirtyrate.c
> @@ -0,0 +1,63 @@
> +/*
> + * Dirtyrate implement code
> + *
> + * Copyright (c) 2017-2020 HUAWEI TECHNOLOGIES CO.,LTD.
> + *
> + * Authors:
> + *  Chuan Zheng <zhengchuan@huawei.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "dirtyrate.h"
> +
> +static uint64_t sample_pages_per_gigabytes = DIRTYRATE_DEFAULT_SAMPLE_PAGES;
> +static uint64_t dirty_rate; /* MB/s */
> +CalculatingDirtyRateStage calculating_dirty_rate_stage = CAL_DIRTY_RATE_INIT;
> +
> +static bool calculate_dirtyrate(struct dirtyrate_config config,
> +                        uint64_t *dirty_rate, int64_t time)
> +{
> +    /* todo */
> +    return true;

It would be better to make this return false until you fill it in!

> +}
> +
> +static void set_dirty_rate(uint64_t drate)
> +{
> +    dirty_rate = drate;
> +}
> +
> +/*
> + * There are multithread will write/read *calculating_dirty_rate_stage*,
> + * we can protect only one thread write/read it by libvirt api.
> + * So we don't add mutex_lock to protect it here, but we must calculate
> + * dirty_rate by libvirt api.
> + */
> +static void set_dirty_rate_stage(CalculatingDirtyRateStage ratestage)
> +{
> +    calculating_dirty_rate_stage = ratestage;
> +}

I don't think I understand the threading comment here; when you say the
'libvirt api' do youmean QMP?  Maybe you could do this with an
atomic_cmpxchg like we do in migrate_set_state?

> +
> +void *get_dirtyrate_thread(void *arg)
> +{
> +    struct dirtyrate_config config = *(struct dirtyrate_config *)arg;
> +    uint64_t dirty_rate;
> +    uint64_t hash_dirty_rate;
> +    bool query_succ;
> +    int64_t msec = 0;
> + 
> +    set_dirty_rate_stage(CAL_DIRTY_RATE_ING);
> +
> +    query_succ = calculate_dirtyrate(config, &hash_dirty_rate, msec);
> +    if (!query_succ) {
> +        dirty_rate = 0;
> +    } else {
> +        dirty_rate = hash_dirty_rate;
> +    }
> +
> +    set_dirty_rate(dirty_rate);
> +    set_dirty_rate_stage(CAL_DIRTY_RATE_END);
> +
> +    return NULL;
> +}
> diff --git a/migration/dirtyrate.h b/migration/dirtyrate.h
> new file mode 100644
> index 0000000..9a5c228
> --- /dev/null
> +++ b/migration/dirtyrate.h
> @@ -0,0 +1,38 @@
> +/*
> + *  Dirtyrate common functions
> + *
> + *  Copyright (c) 2020 HUAWEI TECHNOLOGIES CO., LTD.
> + *
> + *  Authors:
> + *  Chuan Zheng <zhengchuan@huawei.com>
> + *
> + *  This work is licensed under the terms of the GNU GPL, version 2 or later.
> + *  See the COPYING file in the top-level directory.
> + */
> +
> +#ifndef QEMU_MIGRATION_DIRTYRATE_H
> +#define QEMU_MIGRATION_DIRTYRATE_H
> +
> +/* take 256 pages per GB for cal dirty rate */
> +#define DIRTYRATE_DEFAULT_SAMPLE_PAGES    256
> +
> +struct dirtyrate_config {
> +    uint64_t sample_pages_per_gigabytes;
> +    int64_t sample_period_seconds;
> +};
> +
> +/*
> + *  To record calculate dirty_rate status:
> + *  0: initial status, calculating thread is not be created here.
> + *  1: calculating thread is created.
> + *  2: calculating thread is end, we can get result.
> + */
> +typedef enum {
> +    CAL_DIRTY_RATE_INIT  = 0,
> +    CAL_DIRTY_RATE_ING   = 1,

I'm not sure why ING?


> +    CAL_DIRTY_RATE_END   = 2,
> +} CalculatingDirtyRateStage;
> +
> +void *get_dirtyrate_thread(void *arg);
> +#endif
> +
> -- 
> 1.8.3.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK