On Mon, Feb 23, 2009 at 2:02 PM, <david@xxxxxxx> wrote: > On Fri, 20 Feb 2009, David Rees wrote: > >> On Fri, Feb 20, 2009 at 1:34 PM, Battle Mage <battlemage@xxxxxxxxx> wrote: >>> >>> The amount of tps almost doubled, which is good, but i'm worried about >>> the >>> load. For my application, a load increase is bad and I'd like to keep it >>> just like in 8.2.6 (a load average between 3.4 and 4.3). What parameters >>> should I work with to decrease the resulting load average at the expense >>> of >>> tps? >> >> Why is it bad? High load can mean a number of things. >> >> The only way to reduce the load is to get the client to submit >> requests slower. I don't think you'll be successful in tuning the >> database to run slower. I think you're headed in the wrong direction. > > note that on linux the loadave includes processes that are stalled waiting > for I/O to complete. as a result loadave isn't the entire picture. you need > to also look to see what the cpu idle time looks like. > > that being said, I am generally very happy with loadave <= # cores and > consider loadave <= 2x # cores to be acceptable > > it's nowhere near perfect, but it seems to serve me well as a rule of thumb. And it's very dependent on type of load. For our primary customer data database a load of 80 to 120 is not uncommon during certain operations (like adding a slave back to the fark and it gets a ton of requests while it's loading up its cache) and it stays responsive. OTOH, a load of 20 on a reporting server doing tons of sequential scans and allocating a lot of memory is way overloaded for the same server type. I had responsive behaviour into the 300 or 400 load range running pgbench in "destroy all servers mode (-c 500 -t 10000000 or something like that) on that machine. Sure, it wasn't exactly peppy or anything, but most small queries were still running in well under a second. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
