Tarantool development patches archive
 help / color / mirror / Atom feed
From: Konstantin Osipov <kostja@tarantool.org>
To: tarantool-patches@freelists.org
Subject: [tarantool-patches] Re: [PATCH 7/9] vinyl: randomize range compaction to avoid IO load spikes
Date: Tue, 5 Feb 2019 20:39:58 +0300	[thread overview]
Message-ID: <20190205173958.GG6811@chai> (raw)
In-Reply-To: <20190122125458.cutoz5rtfd2sb6el@esperanza>

* 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? 


-- 
Konstantin Osipov, Moscow, Russia, +7 903 626 22 32
http://tarantool.io - www.twitter.com/kostja_osipov

  reply	other threads:[~2019-02-05 17:40 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     ` Konstantin Osipov [this message]
2019-02-06  8:53       ` [tarantool-patches] " Vladimir Davydov
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190205173958.GG6811@chai \
    --to=kostja@tarantool.org \
    --cc=tarantool-patches@freelists.org \
    --subject='[tarantool-patches] Re: [PATCH 7/9] vinyl: randomize range compaction to avoid IO load spikes' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox