Dmitriy, I’m surprised to hear that Random-LRU works at the entry level when Ignite persistence is off. Frankly, this section confuses a lot: https://cwiki.apache.org/confluence/display/IGNITE/Ignite+Durable+Memory+-+under+the+hood#IgniteDurableMemory-underthehood-Entryeviction <https://cwiki.apache.org/confluence/display/IGNITE/Ignite+Durable+Memory+-+under+the+hood#IgniteDurableMemory-underthehood-Entryeviction>
While it was assumed that the entry-based eviction works only for on-heap caches: https://apacheignite.readme.io/docs/evictions <https://apacheignite.readme.io/docs/evictions> Alex G., please chime in and clarify the misunderstanding. — Denis > On Feb 2, 2018, at 4:01 AM, Dmitry Pavlov <dpavlov....@gmail.com> wrote: > > Hi Val, > > I think it is quite accurate because eviction in case PDS enabled or not > has quite different purposes. > > 1. Let us consider PDS enabled and page eviction occurs. First of all it is > page based eviction, but not entry-based. Actually data is not removed, but > only written to disk. We can address this page later by ID. > PDS eviction is primarily the replacement of pages from memory to page on > disk. This eviction policy should ensure the maximum performance of the > solution in the future. There is no data removal from grid in this case. > And Ignite does not allow users to configure the policy. If benchmarks show > that a change in policy results in increased performance, then we can > switch policy. > > 2. Entry-based eviction (if there is no persistence is available) is > slithly different. User will need to reload data into grid in case entry is > evicted but required in cache. In that case Ignite provides selection of > policies. > > Sincerely, > Dmirtiy Pavlov > > > > чт, 1 февр. 2018 г. в 22:24, Valentin Kulichenko < > valentin.kuliche...@gmail.com>: > >> Guys, >> >> Thanks for responses. But I still fail to understand how it affects a user. >> >> Are you saying that with persistence enabled Random-LRU is always used >> regardless of what is specified in pageEvictionMode, while in in-memory >> only scenario we can also utilize Random-2-LRU for eviction? Is this >> accurate? Are there any other differences? >> >> -Val >> >> On Thu, Feb 1, 2018 at 5:01 AM, Dmitry Pavlov <dpavlov....@gmail.com> >> wrote: >> >>> Hi Vyacheslav, >>> >>> Yes, this is right, but for now PDS page based eviction uses Random-LRU, >>> not Random-2-LRU. Something may be changed in future Ignite releases, but >>> now Random-LRU is used. I am going to research if there is some room for >>> improvements in this aspect (e.g. IGNITE-7507 recenly found). >>> >>> If clean page is evicted, nothing really happends. If dirty page is >> evicted >>> from region during checkpointing process run, page is stored in file >> before >>> eviction >>> >>> Some info about this can be found in >>> https://cwiki.apache.org/confluence/display/IGNITE/ >>> Ignite+Durable+Memory+-+under+the+hood#IgniteDurableMemory- >>> underthehood-Pagebasedeviction >>> >>> Sincerely, >>> Dmitriy Pavlov >>> >>> чт, 1 февр. 2018 г. в 9:53, Vyacheslav Daradur <daradu...@gmail.com>: >>> >>>> Hi Valentin, >>>> >>>> As far as I know, when persistence is enabled and Ignite can't >>>> allocate new page-memory in the memory segment, then Ignite >>>> automatically evict some data from RAM to PDS using Random-2-LRU >>>> eviction algorithm. And there are no mechanisms to evict entries out >>>> when PDS is enabled. >>>> >>>> I'll be glad if I am not right and someone will correct me because, as >>>> Ignite user, I can't use PDS only as RAM disk replication for the use >>>> case in my project. >>>> >>>> >>>> On Thu, Feb 1, 2018 at 3:53 AM, Valentin Kulichenko >>>> <valentin.kuliche...@gmail.com> wrote: >>>>> Folks, >>>>> >>>>> On "Eviction Policies" documentation page [1] we have the following >>>> callout: >>>>> >>>>>> Configured eviction policy has no effect if Ignite persistence is >>>> enabled >>>>>> Note that if Ignite Persistence is enabled, then the page-based >>>> evictions >>>>> have no effect because the oldest pages will be purged from memory >>>>> automatically. >>>>> >>>>> This really confuses me. Why is there a difference in how data is >>> evicted >>>>> from memory depending on having disk enabled or not? And how does >>>> eviction >>>>> work with persistence enabled then? >>>>> >>>>> Does anyone can clarify? >>>>> >>>>> [1] https://apacheignite.readme.io/docs/evictions >>>>> >>>>> -Val >>>> >>>> >>>> >>>> -- >>>> Best Regards, Vyacheslav D. >>>> >>> >>
