Date: Fri, 3 Jul 2020 16:35:54 +0300 From: Nick Kostirya <nikolay.kostirya@i11.co> To: freebsd-stable@freebsd.org Subject: Re: BerkeleyDB Hash vs Btree on FreeBSD and Linux Message-ID: <20200703163554.68a87960@i11.co> In-Reply-To: <CAKBkRUxXJJA6K5t7_op0iAZGrurtoZq23%2BsV4DywjVrnCdueMw@mail.gmail.com> References: <20200701130649.0b0643d5@i11.co> <CAKBkRUwnc9aC00NasdMX=g8n1jhiXvfPDwjKaz2sYbB4Hspk5g@mail.gmail.com> <20200701150654.74775e56@i11.co> <CAKBkRUxXJJA6K5t7_op0iAZGrurtoZq23%2BsV4DywjVrnCdueMw@mail.gmail.com>
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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 <lwhsu@freebsd.org> wrote: > On Wed, Jul 1, 2020 at 8:07 PM Nick Kostirya via freebsd-stable > <freebsd-stable@freebsd.org> wrote: > > > > On Wed, 1 Jul 2020 18:20:19 +0800 > > Li-Wen Hsu <lwhsu@freebsd.org> wrote: > > > > > On Wed, Jul 1, 2020 at 6:07 PM Nick Kostirya via freebsd-stable > > > <freebsd-stable@freebsd.org> 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 > _______________________________________________ > freebsd-stable@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org"
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