Date: Mon, 03 Oct 2011 00:33:15 +0200 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-fs@freebsd.org Subject: Re: is TMPFS still highly experimental? Message-ID: <j6aorc$hf0$1@dough.gmane.org> In-Reply-To: <CAGMYy3sCCxOiVqeP4PVbvxnpcyoyQZoL%2Bw3nY8STYnpUNfj6JQ@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>
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On 02/10/2011 07:27, Xin LI wrote: > The problem Ivan have asserted was not confirmed by anyone who have > swap configured properly. Gleb have pointed out that it might be > related to a series of integer overflow by the way (he have also fixed > a lot of tmpfs issues by the way). Well, instead of guessing I can point you to the way I got the original situation - you said you have ZFS configured so it would be easy for you to check. You should to something like this: - configure your system to the best of your abilities (but post what you did different from the defaults) - install postgresql (8.4+, but I don't think the version is important), configure it so it gets half the system memory or 2/3 the system memory for its shared_buffers. - install pgbench - initialize pgbench so that the database definitely is larger than the entire memory you got (NOTE: THIS IS NOT A CONTRIVED TEST - lots of databases in practice are larger than the RAM in the server). - run pgbench & observe the results. 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! (for more info on pgbench, see this: http://www.westnet.com/~gsmith/content/postgresql/pgbench-scaling.htm).
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