From: Vladimir Davydov <vdavydov.dev@gmail.com>
To: Konstantin Osipov <kostja@tarantool.org>
Cc: tarantool-patches@freelists.org
Subject: Re: [tarantool-patches] Re: [PATCH 7/9] vinyl: randomize range compaction to avoid IO load spikes
Date: Wed, 6 Feb 2019 11:53:02 +0300 [thread overview]
Message-ID: <20190206085302.3xzjz2udfvdin5ld@esperanza> (raw)
In-Reply-To: <20190205173958.GG6811@chai>
On Tue, Feb 05, 2019 at 08:39:58PM +0300, Konstantin Osipov wrote:
> * Vladimir Davydov <vdavydov.dev@gmail.com> [19/01/22 15:56]:
> > I ran some tests and, surprisingly, it turned out that randomization
> > didn't help at all: the compaction queue size jumped up to 30% and even
> > 40% from time to time although there was plenty of compaction power -
> > compaction threads were busy only half of the time. When I looked
> > closer, I saw that the queue size behavior looked weird - it jumped
> > after a dump for a very short period of time, until the next dump, which
> > pushed it back to 10%. This made me wonder how it could happen at all -
> > normally, compaction queue should only grow after a dump, not diminish.
>
> > I think I've finally found the root cause of the problem. The code
> > computing compaction priority (see vy_range_update_compaction_priority)
> > is unstable meaning the size of the first level equals the size of the
> > smallest run so if memory dumps produce runs of varying sizes, which is
> > what happens in practice in contrast to simulation, the shape of the
> > tree will vary as well, resulting in different compaction priority and
> > unstable queue behavior.
> >
> > We must fix this somehow. One way to do it is compute the first level
> > size basing on the size of the last level run, which is constant most of
> > the time, and indeed, when I did it and reran the tests, I found that
> > the queue stayed below 10% all the time. Turning off randomization, made
> > the queue jump up to 30%, which was expected. The diff is below. I'll
> > spruce it up a little, wrap it nicely, and submit it separately later.
>
> Why not use a simple weighted average?
Over how many dumps? What do we do after restart, when there's no
history and perhaps even no level 1?
next prev parent reply other threads:[~2019-02-06 8:53 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-20 21:16 [PATCH 0/9] vinyl: compaction randomization and throttling Vladimir Davydov
2019-01-20 21:17 ` [PATCH 1/9] vinyl: update lsm->range_heap in one go on dump completion Vladimir Davydov
2019-01-24 16:55 ` Vladimir Davydov
2019-02-05 16:37 ` [tarantool-patches] " Konstantin Osipov
2019-01-20 21:17 ` [PATCH 2/9] vinyl: ignore unknown .run, .index and .vylog keys Vladimir Davydov
2019-01-24 16:56 ` Vladimir Davydov
2019-01-20 21:17 ` [PATCH 3/9] vinyl: use uncompressed run size for range split/coalesce/compaction Vladimir Davydov
2019-01-21 9:42 ` Vladimir Davydov
2019-02-05 16:49 ` [tarantool-patches] " Konstantin Osipov
2019-02-06 8:55 ` Vladimir Davydov
2019-02-06 10:46 ` Konstantin Osipov
2019-02-06 10:55 ` Vladimir Davydov
2019-02-05 16:43 ` Konstantin Osipov
2019-02-06 16:48 ` Vladimir Davydov
2019-01-20 21:17 ` [PATCH 4/9] vinyl: rename lsm->range_heap to max_compaction_priority Vladimir Davydov
2019-01-20 21:17 ` [PATCH 5/9] vinyl: keep track of dumps per compaction for each LSM tree Vladimir Davydov
2019-02-05 16:58 ` [tarantool-patches] " Konstantin Osipov
2019-02-06 9:20 ` Vladimir Davydov
2019-02-06 16:54 ` Vladimir Davydov
2019-01-20 21:17 ` [PATCH 6/9] vinyl: set range size automatically Vladimir Davydov
2019-01-22 9:17 ` Vladimir Davydov
2019-02-05 17:09 ` [tarantool-patches] " Konstantin Osipov
2019-02-06 9:23 ` Vladimir Davydov
2019-02-06 17:04 ` Vladimir Davydov
2019-01-20 21:17 ` [PATCH 7/9] vinyl: randomize range compaction to avoid IO load spikes Vladimir Davydov
2019-01-22 12:54 ` Vladimir Davydov
2019-02-05 17:39 ` [tarantool-patches] " Konstantin Osipov
2019-02-06 8:53 ` Vladimir Davydov [this message]
2019-02-06 10:44 ` Konstantin Osipov
2019-02-06 10:52 ` Vladimir Davydov
2019-02-06 11:06 ` Konstantin Osipov
2019-02-06 11:49 ` Vladimir Davydov
2019-02-06 13:43 ` Konstantin Osipov
2019-02-06 14:00 ` Vladimir Davydov
2019-02-05 17:14 ` Konstantin Osipov
2019-01-20 21:17 ` [PATCH 8/9] vinyl: introduce quota consumer types Vladimir Davydov
2019-01-20 21:17 ` [PATCH 9/9] vinyl: throttle tx to ensure compaction keeps up with dumps Vladimir Davydov
2019-01-21 14:14 ` Vladimir Davydov
2019-01-22 9:09 ` Vladimir Davydov
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