Re: stupid question about shmmax, shmmni and shmall...
I bookmarked a fairly decent description of these parameters a while back: http://www.puschitz.com/TuningLinuxForOracle.shtml#SettingSharedMemory Maybe you already know this, but you can also set these parameters in /etc/sysctl.conf. That way they persist between reboots, etc. -Ron- 2009-03-05_13:43:30-0500 Giacomo Mulas : > Hello, I am trying to run a demanding quantum chemistry program on a cluster > of multiprocessor machines. Each machine has 2 dual-core opterons and 16Gb > of RAM, and is running a 64 bit kernel (currently 2.6.26) and userspace > (lenny) system. Interprocess communications among processes on the same > node go via shared memory (a lot of it), hence I need to set it to the > maximum possible. > > Can somebody tell me what are the maximum supported values for shmmax, > shmmni and shmall (I know I can set them via /proc/sys/kernel pseudofiles) > or (even better!) tell me how I can calculate them? Is it likely that a > too large value of shmmax or the other two can cause applications to > segfault? > > Thanks in advance, > Giacomo Mulas > > -- > _ > > Giacomo Mulas > _ > > OSSERVATORIO ASTRONOMICO DI CAGLIARI > Str. 54, Loc. Poggio dei Pini * 09012 Capoterra (CA) > > Tel. (OAC): +39 070 71180 248 Fax : +39 070 71180 222 > Tel. (UNICA): +39 070 675 4916 > _ > > "When the storms are raging around you, stay right where you are" > (Freddy Mercury) > _ > > -- > This message has been scanned for viruses and > dangerous content by MailScanner, and is > believed to be clean. > > > -- > To UNSUBSCRIBE, email to debian-amd64-requ...@lists.debian.org > with a subject of "unsubscribe". Trouble? Contact > listmas...@lists.debian.org -- To UNSUBSCRIBE, email to debian-amd64-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
Re: "big" machines running Debian?
2009-02-26_14:21:54-0500 "Douglas A. Tutty" : > On Wed, Feb 25, 2009 at 08:53:45PM -0600, Ron Johnson wrote: > > On 02/25/2009 07:22 PM, Douglas A. Tutty wrote: > > [snip] > > > > > >/proc/megaraid/hba0/raiddrives-0-9 > > >Logical drive: 0:, state: optimal > > >Span depth: 1, RAID level: 1, Stripe size: 64, Row size: 2 > > >Read Policy: Adaptive, Write Policy: Write thru, Cache Policy: Cached IO > > > > > >Logical drive: 1:, state: optimal > > >Span depth: 0, RAID level: 0, Stripe size:128, Row size: 0 > > >Read Policy: No read ahead, Write Policy: Write thru, Cache Policy: Cached > > >IO > > > > Why is Read Ahead disabled on Logical Drive 1? > > My understanding is that "read ahead" in this case refers to the ability > of the raid card to read ahead from one disk while a read is taking > place on another disk. This only makes sense in a redundant raid level. > LD1 is raid0, so there is no other disk from which to read ahead. My understanding is that read ahead means the controller reads more data into memory than you asked for, expecting that the next bits you ask for will be immediately after the ones you just got. -- Ron Peterson Network & Systems Manager Mount Holyoke College http://www.mtholyoke.edu/~rpeterso - I wish my computer would do what I want it to do - not what I tell it to do. -- To UNSUBSCRIBE, email to debian-amd64-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
