Re: BerkeleyDB Hash vs Btree on FreeBSD and Linux
The question is being removed.
I found out that the big difference is only for the HDD, but not for the SSD.
And the difference is very noticeable on long values (> 5000).
But I still did not find the conditions when the hash is better.
I will use only btree from now.
On Thu, 2 Jul 2020 00:00:42 +0800
Li-Wen Hsu wrote:
> On Wed, Jul 1, 2020 at 8:07 PM Nick Kostirya via freebsd-stable
> wrote:
> >
> > On Wed, 1 Jul 2020 18:20:19 +0800
> > Li-Wen Hsu wrote:
> >
> > > On Wed, Jul 1, 2020 at 6:07 PM Nick Kostirya via freebsd-stable
> > > wrote:
> > > >
> > > > Hello.
> > > >
> > > > I noticed that BerkeleyDB Hash is VERY slow compared to BerkeleyDB
> > > > Btree on FreeBSD (UFS or ZFS).
> > > > But they (Hash and Btree) have roughly the same performance on Linux.
> > > >
> > > > Why?
> > >
> > > It's not an easy question, do you have more information about the test
> > > environment setup, and the statistics of the results?
>
> Any information about this?
>
> > > I'd recommend using some analysis tools like DTrace to check what it's
> > > busy for.
> >
> >
> > The top show getblk status often.
> >
> > Please tell me what you can and how to look with DTrace.
> >
> > I use
> > dtrace -n '::: /execname == "a.out"/ { @[probefunc] = count(); }'
> >
> > but I do not see the difference between Hash and Btree.
>
> I would say check the flame graph:
> http://www.brendangregg.com/blog/2015-03-10/freebsd-flame-graphs.html
> There is benchmarks/flamegraph port but I haven't used it for a while.
>
> Li-Wen
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Re: BerkeleyDB Hash vs Btree on FreeBSD and Linux
On Wed, Jul 1, 2020 at 8:07 PM Nick Kostirya via freebsd-stable
wrote:
>
> On Wed, 1 Jul 2020 18:20:19 +0800
> Li-Wen Hsu wrote:
>
> > On Wed, Jul 1, 2020 at 6:07 PM Nick Kostirya via freebsd-stable
> > wrote:
> > >
> > > Hello.
> > >
> > > I noticed that BerkeleyDB Hash is VERY slow compared to BerkeleyDB Btree
> > > on FreeBSD (UFS or ZFS).
> > > But they (Hash and Btree) have roughly the same performance on Linux.
> > >
> > > Why?
> >
> > It's not an easy question, do you have more information about the test
> > environment setup, and the statistics of the results?
Any information about this?
> > I'd recommend using some analysis tools like DTrace to check what it's busy
> > for.
>
>
> The top show getblk status often.
>
> Please tell me what you can and how to look with DTrace.
>
> I use
> dtrace -n '::: /execname == "a.out"/ { @[probefunc] = count(); }'
>
> but I do not see the difference between Hash and Btree.
I would say check the flame graph:
http://www.brendangregg.com/blog/2015-03-10/freebsd-flame-graphs.html
There is benchmarks/flamegraph port but I haven't used it for a while.
Li-Wen
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Re: BerkeleyDB Hash vs Btree on FreeBSD and Linux
On Wed, 1 Jul 2020 18:20:19 +0800
Li-Wen Hsu wrote:
> On Wed, Jul 1, 2020 at 6:07 PM Nick Kostirya via freebsd-stable
> wrote:
> >
> > Hello.
> >
> > I noticed that BerkeleyDB Hash is VERY slow compared to BerkeleyDB Btree on
> > FreeBSD (UFS or ZFS).
> > But they (Hash and Btree) have roughly the same performance on Linux.
> >
> > Why?
>
> It's not an easy question, do you have more information about the test
> environment setup, and the statistics of the results?
>
> I'd recommend using some analysis tools like DTrace to check what it's busy
> for.
The top show getblk status often.
Please tell me what you can and how to look with DTrace.
I use
dtrace -n '::: /execname == "a.out"/ { @[probefunc] = count(); }'
but I do not see the difference between Hash and Btree.
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Re: BerkeleyDB Hash vs Btree on FreeBSD and Linux
On Wed, Jul 1, 2020 at 6:07 PM Nick Kostirya via freebsd-stable wrote: > > Hello. > > I noticed that BerkeleyDB Hash is VERY slow compared to BerkeleyDB Btree on > FreeBSD (UFS or ZFS). > But they (Hash and Btree) have roughly the same performance on Linux. > > Why? It's not an easy question, do you have more information about the test environment setup, and the statistics of the results? I'd recommend using some analysis tools like DTrace to check what it's busy for. Li-Wen ___ [email protected] mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[email protected]"
