Also, note this line from the RedHat doc: *Note that this setting will only stay in effect until the next time the machine is booted. If you wish this setting to be permanent, add the following line to **/etc/sysctl.conf**:*
* * * vm.pagecache = 1 15 80* On Thu, Feb 11, 2010 at 9:23 AM, Christian Paro <[email protected]>wrote: > Your answer might lie with */proc/sys/vm/pagecache:* > * > * > *http://kbase.redhat.com/faq/docs/DOC-7055* > > http://www.ibm.com/developerworks/linux/library/l-adfly.html > > > On Thu, Feb 11, 2010 at 9:19 AM, Martin, Terry R. (CMS/CTR) (CTR) < > [email protected]> wrote: > >> HI Offer, >> >> Unfortunately this is the way it works under z/Linux. Of course because >> of the way z/VM tries to Share memory once memory for a z/Linux guest is >> pushed into cache it is not considered when z/VM is trying to manage the >> memory by taking from one to give to another, it limits z/VM in its' >> memory management process. In Linux he sees having a bunch o f cache as >> a good thing because he has use of the cache and allows in most cases >> for better performance. So as you can see there is a conflict here. The >> hope is that these types of conflicts including double paging due to the >> same LRU approach used by both z/Linux and z/VM, as well as a way to >> dynamically prioritize the workloads for not only z/VM but for processes >> running in z/Linux can be resolved. >> >> Anyway for now the best approach for the cache is to try to size the >> memory of the z/Linux guest to where you just see a very small amount of >> SWAPPING and make this SWAPPING go to VDISK. VDISK SWAPPING is a memory >> speed in z/VM so it is very fast. This will set the behavior so that >> z/Linux does not cache. I know from my own experiences that this is not >> always an easy thing to nail down but for the most part I have been able >> to balance this between the OSs'. >> >> Thank You, >> >> Terry Martin >> Lockheed Martin - Citic >> z/OS and z/VM Performance Tuning and Operating Systems Support >> Office - 443 348-2102 >> Cell - 443 632-4191 >> >> >> -----Original Message----- >> From: Linux on 390 Port [mailto:[email protected]] On Behalf Of >> Offer Baruch >> Sent: Thursday, February 11, 2010 8:18 AM >> To: [email protected] >> Subject: Linux file system cache >> >> Hi all, >> >> One of the problems with Linux under VM (not just z/VM I guess) is that >> no >> matter how much memory you allocate to the guest it will consume it all >> as >> cache. >> It just seems reasonable to be able to limit this cache to a user >> defined >> value leaving the rest of it for the applications. >> Sadly I couldn't find a parameter to enforce this limit. >> So, my question is, is there a way to limit the cache? If not, why? >> Obviously this caching method is just not good enough under VM. >> Decreasing and increasing memory for a guest is quite disruptive and >> adding >> 100M to an oracle guest just looks bad :-) >> >> Thanks! >> Offer Baruch >> >> No virus found in this outgoing message. >> Checked by AVG - www.avg.com >> Version: 9.0.733 / Virus Database: 271.1.1/2680 - Release Date: 02/10/10 >> 21:38:00 >> >> ---------------------------------------------------------------------- >> For LINUX-390 subscribe / signoff / archive access instructions, >> send email to [email protected] with the message: INFO LINUX-390 or >> visit >> http://www.marist.edu/htbin/wlvindex?LINUX-390 >> >> ---------------------------------------------------------------------- >> For LINUX-390 subscribe / signoff / archive access instructions, >> send email to [email protected] with the message: INFO LINUX-390 or >> visit >> http://www.marist.edu/htbin/wlvindex?LINUX-390 >> > > ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
