On Wed, Mar 18, 2015 at 12:44 AM, Robert Schmelzer <rob...@schmelzer.cc> wrote:
> I do not agree with you on that point. Tapestry is designed to cache the > page. When you do not have enough memory to hold your pages cached > basically the system does not work as designed so you should fail early. > Otherwise you possible defer the problem to production use. Fail early > means you should try to see the problem in the early stages on dev, where > you try out all your pages. As I mentioned in my other post - you would > also not expect the EntityManager to work soft-refereences or spring > application context to work soft referenced. > > That's the definition of a memory cache - it trades memory for better performance. The primary use case for soft refences is for caching so seems to me it works exactly as designed. Your comparison to the EntityManager is flawed since it's created per request. An EntityManager is designed to be inexpensive to create. There are many areas that need improvements in Tapestry but this is not one in my opinion. However, you seem to strongly think otherwise, so you probably have some data to back this up. Do you have a memory dump and trending cpu/memory charts of a sufficiently large system you can share with us to demonstrate the problem? Jvisualvm snapshots should work fine. And furthermore - how would you like this changed? If it's just adding a Page as a threadlocal, perhaps you can just write a patch for it. Kalle > > Am 18.03.2015 um 04:23 schrieb Kalle Korhonen: > > In my opinion, soft referencing page objects is highly appropriate usage >> here. If there's pressure on the available memory, it makes sense to trade >> performance for memory instead of exiting with OoM. This is simple >> condition to detect and should be visible with any reasonable monitoring >> tool. If you are hitting memory limits, you'll need to allocate more >> memory >> for the application for optimal performance. Soft references are >> especially >> useful here because you can optimize its behavior with the -client/-server >> setting depending on your preferences. >> >> Kalle >> >> On Tue, Mar 17, 2015 at 4:26 PM, Howard Lewis Ship <hls...@gmail.com> >> wrote: >> >> Possibly we need something more advanced; our own reference type that can >>> react to memory pressure by discarding pages that haven't been used in >>> configurable amount of time. >>> >>> Or perhaps we could just assume that any page that has been used once >>> need >>> to be used in the future and get rid of the SoftReference entirely (or >>> otherwise janitorize it in some way). >>> >>> On Tue, Mar 17, 2015 at 1:24 AM, Robert Schmelzer <rob...@schmelzer.cc> >>> wrote: >>> >>> Hello, >>>> >>>> I recently came accross the implementation of PageSourceImpl where >>>> PageImpl instances are softly refereneced into the pageCache: >>>> >>>> private final Map<CachedPageKey, SoftReference<Page>> pageCache = >>>> CollectionFactory.newConcurrentMap(); >>>> >>>> This implementation caused troubles, when you bring your system into >>>> memory preassure. The JVM will start to throw away the PageImpl to free >>>> >>> up >>> >>>> memory - but during request processing he needs the PageImpl again and >>>> starts creating it again. So basically you end up loosing your pageCache >>>> >>> at >>> >>>> all and start creating the PageImpl instances on every request, which >>>> >>> take >>> >>>> way to much time and takes load onto the CPU. So basically you are >>>> >>> hiding a >>> >>>> memory problem by making the system slow and raise CPU load. >>>> >>>> I would suggest to use "normal" references for the PageCache or at least >>>> only do SoftReferences only when not in production mode. Otherwise we >>>> are >>>> going to cover memory problems for too long. >>>> >>>> What do you think about that? >>>> >>>> Robert >>>> >>>> --------------------------------------------------------------------- >>>> To unsubscribe, e-mail: users-unsubscr...@tapestry.apache.org >>>> For additional commands, e-mail: users-h...@tapestry.apache.org >>>> >>>> >>>> >>> -- >>> Howard M. Lewis Ship >>> >>> Creator of Apache Tapestry >>> >>> The source for Tapestry training, mentoring and support. Contact me to >>> learn how I can get you up and productive in Tapestry fast! >>> >>> (971) 678-5210 >>> http://howardlewisship.com >>> @hlship >>> >>> > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tapestry.apache.org > For additional commands, e-mail: users-h...@tapestry.apache.org > >
