Re: [HPDD-discuss] OSC and buffer cache throttling

On Feb 3, 2015, at 2:34 PM, "Mohr Jr, Richard Frank (Rick Mohr)" <rmohr(a)utk.edu&gt; wrote: >> On Feb 3, 2015, at 3:26 PM, Drokin, Oleg <oleg.drokin(a)intel.com&gt; wrote: >> >> >> The total amount of cache used by lustre on a client should be controlled by /proc/fs/lustre/llite/<fsname>/max_cached_mb. According to the manual, this defaults to 3/4 of the client RAM. However, on my Cray system, it looks like it is defaulting to 1/2 the RAM (not sure why). From your tests, it looks like the lustre cache is topping out around 1/2 the RAM. Are you running on a Cray client by any chance? > > Recent lustre versions (2.4.0 may be? or was that 2.5.0?) did drop that down to 1/2 indeed, because that shown some performance benefit. > Jinshan probably can elaborate on that in more details. Hmm. My Cray client is running 2.5.1 and has max_cached_mb set to 1/2 RAM. But I have another client running 2.5.3 which sets the parameter to 3/4 of the RAM. Maybe Cray patched their version to change the default value? -- Rick Mohr Senior HPC System Administrator National Institute for Computational Sciences http://www.nics.tennessee.edu