There's also a non-percent-based control as well. My understanding is that segmap_percent doesn't work on some versions or architectures, notably OpenSolaris. On Tue, Dec 27, 2005 at 01:15:39PM -0800, Tom Arthurs wrote: > From http://docs.sun.com/source/817-1836-10/perfplat.html > > High File System Page-in Rate > > If you are seeing high file system page-in rates on Solaris 8 or 9, you > may benefit from increasing the value of segmap_percent. This parameter > is set by adding the following line to the /etc/system file: > > set segmap_percent=25 > > segmap_percent adjusts the percentage of memory that the kernel will map > into its address space for the file system cache. The default value is > 12; that is, the kernel will reserve enough space to map at most 12% of > memory for the file system cache. On a heavily loaded machine with 4 GB > of physical memory, improvements have been seen with values as high as > 60. You should experiment with this value, starting with values around > 25. On systems with large amounts of physical memory, you should raise > this value in small increments, as it can significantly increase kernel > memory requirements. > ==================================== > > I think this can also be set with the kernel debugger. > > I keep it at 50% on my E3500 and E4500 systems (8 and 12 GB memory). > > Jim C. Nasby wrote: > > >On Fri, Dec 23, 2005 at 04:50:32PM +1100, Dan Austin wrote: > > > > > >>>[...] > >>>Right, the file is fully written under a temp name, and then > >>>rename()'d > >>> > >>> > >>This makes sense and is almost certainly not the cause of the problem. > >>Although there is a lot more data being written to that file than I > >>would have thought. > >> > >>One of Sun's kernel engineers has come up with a solution that seems to > >>have fixed the problem. Instead of increasing work_mem (which we still > >>might do) we've mounted a swapfs partition over the pg temp directory: > >> > >> # mount | grep pgsql_tmp > >> /export/data/pgsql/data/base/64920741/pgsql_tmp on swap [...] > >> > >>This has actually reduced the disk activity considerably. So far, the > >>blocking problem seems to have gone. > >> > >>Now to find some Postgres DBAs in Sydney to do some review / tuning of > >>our memory settings. :-) > >> > >> > > > >Note also that Solaris by default limits the amount of memory used for > >disk caching, which is Not Good for PostgreSQL. IIRC this can be changed > >with a sysctl, but I don't recall the details off-hand. > > > > > > > ---------------------------(end of broadcast)--------------------------- > TIP 3: Have you checked our extensive FAQ? > > http://www.postgresql.org/docs/faq > -- Jim C. Nasby, Sr. Engineering Consultant jnasby@xxxxxxxxxxxxx Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
