From: Vladimir Davydov <vdavydov.dev@gmail.com>
To: Konstantin Osipov <kostja@tarantool.org>
Cc: tarantool-patches@freelists.org
Subject: Re: [tarantool-patches] Re: [PATCH 6/9] vinyl: set range size automatically
Date: Wed, 6 Feb 2019 20:04:23 +0300 [thread overview]
Message-ID: <20190206170423.4dv7slwyecuubdqt@esperanza> (raw)
In-Reply-To: <20190206092331.tpqfx2odv45fqqlx@esperanza>
On Wed, Feb 06, 2019 at 12:23:31PM +0300, Vladimir Davydov wrote:
> On Tue, Feb 05, 2019 at 08:09:09PM +0300, Konstantin Osipov wrote:
> > * Vladimir Davydov <vdavydov.dev@gmail.com> [19/01/21 06:58]:
> > > +int64_t
> > > +vy_lsm_range_size(struct vy_lsm *lsm)
> > > +{
> > > + /* Use the configured range size if available. */
> > > + if (lsm->opts.range_size > 0)
> > > + return lsm->opts.range_size;
> > > + /*
> > > + * It doesn't make much sense to create too small ranges.
> > > + * Limit the max number of ranges per index to 1000 and
> > > + * never create ranges smaller than 16 MB.
> > > + */
> > > + enum { MIN_RANGE_SIZE = 16 * 1024 * 1024 };
> > > + enum { MAX_RANGE_COUNT = 1000 };
> > > + /*
> > > + * Ideally, we want to compact roughly the same amount of
> > > + * data after each dump so as to avoid IO bursts caused by
> > > + * simultaneous major compaction of a bunch of ranges,
> > > + * because such IO bursts can lead to a deviation of the
> > > + * LSM tree from the configured shape and, as a result,
> > > + * increased read amplification. To achieve that, we need
> > > + * to have at least as many ranges as the number of dumps
> > > + * it takes to trigger major compaction in a range.
> > > + */
> > > + int range_count = vy_lsm_dumps_per_compaction(lsm);
> > > + range_count = MIN(range_count, MAX_RANGE_COUNT);
> > > + int64_t range_size = lsm->stat.disk.last_level_count.bytes /
> > > + (range_count + 1);
> > > + range_size = MAX(range_size, MIN_RANGE_SIZE);
> > > + return range_size;
> > > +}
> >
> > OK, you could say the value is rarely used, so can be calculated
> > each time it is used, but why instead not recalculate it on each
> > major compaction? This would spare us from technical debt and
> > having to think about potential performance bottleneck in the
> > future.
>
> Well, okay, I think we can do that, too.
Come to think of it, I'd prefer not to, because this would one more
member to struct vy_lsm, which we would have to update on dump and
compaction - it's more error prone IMO. Since calculation of the target
range size is trivial and called rarely (on split/coalesce), I think we
should leave it as is.
next prev parent reply other threads:[~2019-02-06 17:04 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 [this message]
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
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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