The cache will grow as the data blocks are read in from the filesystem. That is all the cache is used for, storing filesystem data in an easily accessed place. When an application needs more memory the cache will be released to a point.
The symptom that we were seeing was the paging device filling up and cache being depleted. The virtual machine would usually go into a loop. Internally, WebSphere was doing some thrashing on it's own. It was basically in continuous garbage collection, trying to release storage for the needs of the application. It turned out that the application was doing a DB2 query and under certain circumstances did not put any conditions on the query, so the entire table would be read into an object (a 120MB object!). WebSphere dutifully tried to acquire enough storage to hold the whole table, but was not able to do so. It would start garbage collection, release a few objects, then some more rows could be retrieved, on and on, until it couldn't release any more storage. On Wed, 2004-07-28 at 09:51, James Melin wrote: > This is Websphere. What would cause cache to grow constantly, from an > application perspective. What did you see in your application? > > > > Rich Smrcina > <[EMAIL PROTECTED] > o.com> To > Sent by: Linux on [EMAIL PROTECTED] > 390 Port cc > <[EMAIL PROTECTED] > IST.EDU> Subject > Re: Under what conditions will > Linux start releasing Cache? > 07/28/2004 09:39 > AM > > > Please respond to > Linux on 390 Port > <[EMAIL PROTECTED] > IST.EDU> > > > > > > > What is this machine used for? 110 MB of cache is pretty much a waste > of storage. If the machine eats into all (or most) of that before it > finally croaks, then you have a memory hog or leak somewhere. > > I've seen that happen with WebSphere and it turned out to be an > application problem. > > The cache will slowly get released to a certain point, then paging will > begin and the paging/cacheing dance will begin. When the page device > fills and the cache is gone then your up the creek... > > On Wed, 2004-07-28 at 09:25, James Melin wrote: > > I've got a linux guest that is pushing the wall, 17 megs free and > dropping. > > Swapping is going to be inevitable. The problem is that the memory usage > > growth is slow, and that cache grows to 110 meg before we start to > approach > > the wall. Will SLES8 start to release or clean the cache before swapping > > becomes rampant? > > > > <vent_spleen> > > > > Since there seems to be no way to control the cache in SLES8, which > really > > sucks since, in our situation, it is caching unimportant things. None of > > the application data is local. If there are any of the Linux Kernal > > developers monitoring this list, add my voice to those that are telling > you > > that not being able to control cache behavior is a really frustrating > when > > working in a virtualized environment where you are trying to divide > limited > > resources amongst many guests. The Cache behaviour is the biggest > > non-application pig that I can see. > > > > Just my 2 cents > > > > </vent_spleen> > > > > ---------------------------------------------------------------------- > > 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 > -- > Rich Smrcina > illustro Systems International, LLC > --- See The Light--- > Visit www.illustro.com to experience: > z/Web-Host -- Easy Web-enabling for your Mainframe > z/XML-Host -- Easy XML Enablement for your Mainframe > > Tel: +1.214.800.8900 Fax: +1.214.800.8989 > > Catch the WAVV! http://www.wavv.org > WAVV 2005 - Colorado Springs - May 20-24, 2005 > > ---------------------------------------------------------------------- > 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 -- Rich Smrcina illustro Systems International, LLC --- See The Light--- Visit www.illustro.com to experience: z/Web-Host -- Easy Web-enabling for your Mainframe z/XML-Host -- Easy XML Enablement for your Mainframe Tel: +1.214.800.8900 Fax: +1.214.800.8989 Catch the WAVV! http://www.wavv.org WAVV 2005 - Colorado Springs - May 20-24, 2005 ---------------------------------------------------------------------- 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
