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Date:      Mon, 3 Oct 2011 21:37:19 +0200
From:      Ivan Voras <ivoras@freebsd.org>
To:        Xin LI <delphij@gmail.com>
Cc:        freebsd-fs@freebsd.org
Subject:   Re: is TMPFS still highly experimental?
Message-ID:  <CAF-QHFUaTt1bZpDnWWMP49d6t5dhB%2B726NaosN2GzLeSFsRR5A@mail.gmail.com>
In-Reply-To: <CAGMYy3tbMWU6JU1%2B%2B5XmzjZTrV1=oAgRaaDE3-=MMT73F_ojQQ@mail.gmail.com>
References:  <CAOfDtXMm9K_fbOmvG2gvXxDfKakkgpPt9MLifqDxa4wCibMExg@mail.gmail.com> <alpine.GSO.1.10.1110011122030.882@multics.mit.edu> <CADLo83-s_3H8PbbxOPPxbe0m10U0U5JW-feB294dFs%2BQ3iTWvg@mail.gmail.com> <CAGMYy3ssi%2BkAuufDTHA1z6u7jRrZwRRkCCkcO94GHNGF9Rku_w@mail.gmail.com> <20111002020231.GA70864@icarus.home.lan> <CAGMYy3sCCxOiVqeP4PVbvxnpcyoyQZoL%2Bw3nY8STYnpUNfj6JQ@mail.gmail.com> <j6aorc$hf0$1@dough.gmane.org> <CAGMYy3tbMWU6JU1%2B%2B5XmzjZTrV1=oAgRaaDE3-=MMT73F_ojQQ@mail.gmail.com>

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On 3 October 2011 20:37, Xin LI <delphij@gmail.com> wrote:

> It's mostly "normal" configuration -- 6GB RAM, 14GB swap, ZFS as /usr;

> Initialized with pgbench -i -s 500 pgbench.

Ok, this should be enough ~~ 7 GB database on a 6 GB machine.

>> =C2=A0 =C2=A0 =C2=A0 =C2=A0- run pgbench & observe the results.
>
> pgbench -t 20000 -c 64 -S pgbench
>
> Can't seem to reproduce:
>
> # df -Httmpfs
> Filesystem =C2=A0 =C2=A0Size =C2=A0 =C2=A0Used =C2=A0 Avail Capacity =C2=
=A0Mounted on
> tmpfs =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A010G =C2=A0 =C2=A0 69k =C2=A0 =C2=
=A0 10G =C2=A0 =C2=A0 0% =C2=A0 =C2=A0/tmp
>
> Any suggestions?

Can't think of anything to add :) I don't think increasing the
database size would affect it much.

Comparing what you did to my original report at
http://www.mail-archive.com/freebsd-current@freebsd.org/msg126491.html,
it seems like that bug is gone!

But my machine was one of the bigger ones (for that time) - AFAIK 24
GB RAM and many cores (16?). Maybe there is some race condition which
is exposed on large machines.


>> This should create really bad contention problem for memory between
>> postgresql and ZFS, which should manifest itself in tmpfs shrinking to 0
>> bytes free.
>>
>> If you don't get this problem then great, it might be solved!


I don't have the equipment now to test it myself but I agree that
based on what you posted it looks solved.



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