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From: Vladimir Davydov <vdavydov.dev@gmail.com>
To: Konstantin Osipov <kostja@tarantool.org>
Cc: tarantool-patches@freelists.org
Subject: Re: [PATCH 8/8] vinyl: keep track of thread pool idle ratio
Date: Thu, 6 Sep 2018 13:52:16 +0300	[thread overview]
Message-ID: <20180906105216.6ihl5mkvmaisronv@esperanza> (raw)
In-Reply-To: <20180906102631.GI8205@chai>

On Thu, Sep 06, 2018 at 01:26:31PM +0300, Konstantin Osipov wrote:
> * Vladimir Davydov <vdavydov.dev@gmail.com> [18/09/06 11:19]:
> 
> > > > To understand whether the disk is fully utilized or can still handle
> > > > more compaction load and make right decisions regarding transaction
> > > > throttling, we need a metric that would report how much time worker
> > > > threads spent being idle. So this patch adds two new metrics to global
> > > > statistics, disk.dump_idle_ratio and compact_idle_ratio, which show how
> > > > much time dump threads and compaction threads were idle, respectively.
> > > > The metrics are updated using the following formula:
> > > > 
> > > >                        idle_time
> > > >   idle_ratio = --------------------------
> > > >                dump_period * worker_count
> > > 
> > > I don't understand the formula. There can be many workers.
> > > Is idle time measured per worker or per entire pool? 
> > > 
> > > If it is measured per entire pool, how is idle time calculated if
> > > some workers are busy and some not?
> > 
> > It is measured for entire pool - note that I divide the result by
> > worker_count. E.g. if there were two workers and one of them were
> > busy all the time between two last dumps while another were idle,
> > idle_ratio would be 0.5.
> 
> This looks imprecise. Why not measure idle time of each worker and
> then even it out over the total number of workers?

That's exactly what I do. I maintain the idle time for each worker
thread and then divide it by the total number of workers.

> Besides, once again, how do you define the window over which you
> measure?

I use dump period for the window, i.e. time between two subsequent
memory dumps. Respectively, I update the idle_ratio after each memory
dump. I'm planning to update throttle rate limit there too.

  reply	other threads:[~2018-09-06 10:52 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-02 20:18 [PATCH 0/7] vinyl: improve stats for throttling Vladimir Davydov
2018-09-02 20:18 ` [PATCH 1/7] vinyl: fix accounting of secondary index cache statements Vladimir Davydov
2018-09-02 22:26   ` [tarantool-patches] " Konstantin Osipov
2018-09-02 20:18 ` [PATCH 2/7] vinyl: add global memory stats Vladimir Davydov
2018-09-02 22:27   ` [tarantool-patches] " Konstantin Osipov
2018-09-02 22:27   ` Konstantin Osipov
2018-09-03  8:10     ` Vladimir Davydov
2018-09-02 20:18 ` [PATCH 3/7] vinyl: add global disk stats Vladimir Davydov
2018-09-02 22:30   ` [tarantool-patches] " Konstantin Osipov
2018-09-02 20:18 ` [PATCH 4/7] vinyl: fix force compaction logic Vladimir Davydov
2018-09-02 20:18 ` [PATCH 5/7] vinyl: update compact priority usual way on range split/coalesce Vladimir Davydov
2018-09-02 20:18 ` [PATCH 6/7] vinyl: keep track of compaction queue length and debt Vladimir Davydov
2018-09-02 20:19 ` [PATCH 7/7] vinyl: keep track of disk idle time Vladimir Davydov
2018-09-04 11:54   ` Vladimir Davydov
2018-09-04 17:23     ` Vladimir Davydov
2018-09-04 17:23       ` [PATCH 1/8] vinyl: add helper to check whether dump is in progress Vladimir Davydov
2018-09-06  7:33         ` Konstantin Osipov
2018-09-04 17:23       ` [PATCH 2/8] vinyl: don't use mempool for allocating background tasks Vladimir Davydov
2018-09-06  7:33         ` Konstantin Osipov
2018-09-04 17:23       ` [PATCH 3/8] vinyl: factor out worker pool from scheduler struct Vladimir Davydov
2018-09-06  7:34         ` Konstantin Osipov
2018-09-04 17:23       ` [PATCH 4/8] vinyl: move worker allocation closer to task creation Vladimir Davydov
2018-09-06  7:35         ` Konstantin Osipov
2018-09-04 17:23       ` [PATCH 5/8] vinyl: use separate thread pools for dump and compaction tasks Vladimir Davydov
2018-09-06  7:37         ` Konstantin Osipov
2018-09-06  9:48           ` Vladimir Davydov
2018-09-06 10:32             ` Konstantin Osipov
2018-09-04 17:23       ` [PATCH 6/8] vinyl: zap vy_worker_pool::idle_worker_count Vladimir Davydov
2018-09-06  7:38         ` Konstantin Osipov
2018-09-04 17:23       ` [PATCH 7/8] vinyl: don't start scheduler fiber until local recovery is complete Vladimir Davydov
2018-09-06  7:39         ` Konstantin Osipov
2018-09-04 17:23       ` [PATCH 8/8] vinyl: keep track of thread pool idle ratio Vladimir Davydov
2018-09-06  7:49         ` Konstantin Osipov
2018-09-06  8:18           ` Vladimir Davydov
2018-09-06 10:26             ` Konstantin Osipov
2018-09-06 10:52               ` Vladimir Davydov [this message]
2018-09-06 10:57                 ` Konstantin Osipov
2018-09-06 11:59                   ` Vladimir Davydov
2018-09-09 11:41 ` [PATCH 0/7] vinyl: improve stats for throttling Vladimir Davydov

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