On Jul 2, 2013, at 3:32 PM, Radim Vansa <rva...@redhat.com> wrote: > | Given such a scenario, I am not interested at all in synchronous > | storage. Before we commit into a design which is basically assuming > | the need for synchronous storage guarantees, I'd like to understand > | what kind of use case it's aiming to solve. > > You're right that I may miss the wider perspective and that I am too much > focused on storing stuff reliably when we have reliability assured by > multiple owners. > > | > | Only then we would be able to pick a design (or multiple ones); for my > | use case the proposal from Karsten seems excellent, so I'm wondering > | why I should be looking for alternatives, and wondering why everyone > | is still wasting time on different discussions :-D > > Karsten implementation has one major drawback: all the keys are stored > in-memory, and there's no search structure for overflow. For use case we've > had with bigger keys and very small values this is simply not an option. > However, we have the LevelDB JNI implementation for this purpose and the > numbers are not bad in non-syncing mode. Do we want to have some efficient > no-dependency cache-store? If the question is no, okay, let use recommend > LevelDB JNI for this purposes.
That's been my feeling as well. Karten's implementation, in spite of its limitations, is a very good base and kicks performance of our current offering. Sure, it has some drawbacks, but as Radim said, when bigger keys are used, or many keys, we could recommend the LevelDB JNI cache store alternative. Instead of writing a brand new cache store from scratch, it might more valuable to figure out what the threshold is after which the the LevelDB option should be used instead of Karsten's cache store. This could be explored by increasily testing keys of different sizes, and/or different amount of keys stored. WDYT? This way, we can provide better guidance on when to use each one. > > | > | I'm pretty sure there is people looking forward for a synch-CacheStore > | too: if you could nail down such a scenario however I'm pretty sure > | that some other considerations would not be taken into account (like > | consistency of data when reactivating a dormant node), so I suspect > | that just implementing such a component would actually not make any > | new architecture possible, as you would get blocked by other problems > | which need to be solved too.. better define all expectations asap! The starting point has been this: https://issues.jboss.org/browse/ISPN-2806 We need a faster FCS. We already have several options that are faster, we all seem to agree that Karten's FCS and LevelDB JNI offer the best solutions, each with their own caveats. The primary difference between them two, as far as I can see from Radim's performance test results, is the read performance in overflow. Karsten's characteristics makes it incredibly fast here, but there's a limit to it. If we can figure out what that limit is, we have all the info that we can provide to the user: if you store keys with size bigger than X, or store more than Y keys in the cache, use LevelDB JNI, otherwise use Karsten's FCS (which would really be the new FCS). > | > | To me this thread smells of needing the off-heap Direct Memory buffers > | which I suggested [long time ago] to efficiently offload internal > | buffers, > > Yes, when it comes to reducing GC pauses, that is the best option. However, > you can't have enough RAM to handle everything in-memory (off-heap), > persistent storage for overflow is a must-have. > > | but failing to recognise this we're pushing responsibility to > | an epic level complex CacheStore.. guys let's not forget that a mayor > | bottleneck of CacheStores today is the SPI it has to implement, we > | identified several limitations in the contract in the past which > | prevent a superior efficiency: we're working towards a mayor release > | now so I'd rather focus on the API changes which will make it possible > | to get decent performance even without changing any storage engine.. ^ Indeed, that's been discussed in [1], and you've contributed to it, but I think having a faster FCS to start with is a bigger priority than this. Our FCS has been bashed pretty much since day one, and we know have faster alternatives. We just need to come up with the right recommendations on how to use them, and then we can focus on [1]. Also, part of me wants JCache to be finaled before tackling [1], so that we have a stable cacheloader/cachewriter interface at the spec level. I think it's pretty stable now, but you never know. [1] https://community.jboss.org/wiki/CacheLoaderAndCacheStoreSPIRedesign > | I'm pretty sure Cassandra (to pick one) doesn't scale too bad. > > The issues common to all local cache-stores are definitely something to do. I > just don't feel enough into the problematics to handle them myself - that's > why I jumped onto implementing just another cache store. > > Radim > > | > | Cheers, > | Sanne > | > | > | > | On 2 July 2013 10:09, Radim Vansa <rva...@redhat.com> wrote: > | > Hi, > | > > | > I've written down this proposal for the implementation of new cache store. > | > > | > https://community.jboss.org/wiki/BrnoCacheStoreDesignProposal > | > > | > WDYT? > | > > | > Radim > | > > | > ----- Original Message ----- > | > | From: "Radim Vansa" <rva...@redhat.com> > | > | To: "infinispan -Dev List" <infinispan-dev@lists.jboss.org> > | > | Sent: Thursday, June 27, 2013 2:37:43 PM > | > | Subject: Re: [infinispan-dev] Cachestores performance > | > | > | > | > | > | > | > | ----- Original Message ----- > | > | | From: "Galder Zamarreño" <gal...@redhat.com> > | > | | To: "infinispan -Dev List" <infinispan-dev@lists.jboss.org> > | > | | Sent: Thursday, June 27, 2013 1:52:11 PM > | > | | Subject: Re: [infinispan-dev] Cachestores performance > | > | | > | > | | > As for Karsten's FCS implementation, I too have issues with the key > | > | | > set > | > | | > and > | > | | > value offsets being solely in memory. However I think that could be > | > | | > improved by storing only a certain number of keys/offsets in memory, > | > | | > and > | > | | > flushing the rest to disk again into an index file. > | > | | > | > | | ^ Karsten's implementation makes this relatively easy to achieve > | > | | because it > | > | | already keeps this mapping in a LinkedHashMap (with a given max > entries > | > | | limit [1]) assuming removeEldestEntry() is overriden to flush to disk > | > | | older > | > | | entries. Some extra logic would be needed to bring back data from the > | > | | disk > | > | | too… but your suggestion below is also quite interesting... > | > | > | > | I certainly wouldn't call this easy task, because the most problematic > | > | part > | > | is what we will do when the whole entry (both key and value) are gone > | > | from > | > | memory and we want to read them - that requires keeping some searchable > | > | structure on-disk. And that's the hard stuff. > | > | > | > | | > | > | | > I believe LevelDB follows a similar design, but I think Karsten's > FCS > | > | | > will > | > | | > perform better than LevelDB since it doesn't attempt to maintain a > | > | | > sorted > | > | | > structure on disk. > | > | | > | > | | ^ In-memory, the structure can optionally be ordered if it's bound > [1], > | > | | otherwise it's just a normal map. How would be store it at the disk > | > | | level? > | > | | B+ tree with hashes of keys and then linked lists? > | > | > | > | Before choosing "I love B#@& trees, let's use B#@& trees!", I'd find out > | > | what > | > | requirements do we have for the structure. I believe that the index > | > | itself > | > | should not be considered persistent, as it can be rebuilt when > preloading > | > | the data (sequentially reading the data is fast, therefore we can afford > | > | do > | > | this indexing preload), the reason of the index being on-disk is that we > | > | don't have enough memory to store all keys, or even key hashes. > Therefore > | > | it > | > | does not have to be updated synchronously with the writes. It should be > | > | mostly read-optimized then, because that's the thing where we need > | > | synchronous access to this structure. > | > | > | > | | > | > | | > One approach to maintaining keys and offsets in memory could be a > | > | | > WeakReference that points to the key stored in the in-memory > | > | | > DataContainer. Once evicted from the DC, then the CacheStore impl > | > | | > would > | > | | > need to fetch the key again from the index file before looking up > the > | > | | > value in the actual store. > | > | | > | > | | ^ Hmmm, interesting idea… has the potential to safe the memory space > by > | > | | not > | > | | having to keep that extra data structure in the cache store. > | > | > | > | You mean to mix the DataContainer with xCacheEntry implementation and > the > | > | cache store implementation? Is that possible from design perspective? > | > | Speaking about different kind of references, we may even optimize > | > | not-well-tuned eviction by SoftReferences, so that even if the entry was > | > | evicted from main DataContainer, we'd keep the value referenced from the > | > | cache-store (and this does not have to be loaded from disk if referenced > | > | before garbage collection). But such thought may be premature > | > | optimization. > | > | For having eviction managed in relation with GC we should rather combine > | > | this with PhantomReferences, where entries would be written to cache > upon > | > | finalization. > | > | > | > | | > | > | | > This way we have hot items always in memory, semi-hot items with > | > | | > offsets > | > | | > in > | > | | > memory and values on disk, and cold items needing to be read off > disk > | > | | > entirely (both offset and value). Also for write-through and > | > | | > write-behind, as long as the item is hot or warm (key and offset in > | > | | > memory), writing will be pretty fast. > | > | | > | > | | My worry about Karsten's impl is writing actually. If you look at the > | > | | last > | > | | performance numbers in [2], where we see the performance difference of > | > | | force=true and force=false in Karsten's cache store compared with > | > | | LevelDB > | > | | JNI, you see that force=false is fastest, then JNI LevelDB, and the > | > | | force=true. Me wonders what kind of write guarantees LevelDB JNI > | > | | provides > | > | | (and the JAVA version)... > | > | > | > | Just for clarification: the fast implementation is without force at all, > | > | the > | > | slower is with force(false). Force(true) means updating metadata (such > as > | > | access times?) which is not required for cache-store. > | > | But the numbers suggest that the random access with syncing is really > not > | > | a > | > | good option, and that we should rather use the temporary append-only > log, > | > | which would be persisted into structured DB by different thread (as > | > | LevelDB > | > | does, I suppose). > | > | > | > | Thinking about all the levels and cache structures optimizing the read > | > | access, I can see four levels of search structures: key + value (usual > | > | DataContainer), key + offset, hash + offset, all on disk. The "hash + > | > | offset" may seem superflous but for some use-cases with big keys it may > | > | be > | > | worth sparing a few disk look-ups. > | > | > | > | Radim > | > | > | > | | > > | > | | > On 27 Jun 2013, at 10:33, Radim Vansa <rva...@redhat.com> wrote: > | > | | > > | > | | >> Oops, by the cache store I mean the previously-superfast > | > | | >> KarstenFileCacheStore implementation. > | > | | >> > | > | | >> ----- Original Message ----- > | > | | >> | From: "Radim Vansa" <rva...@redhat.com> > | > | | >> | To: "infinispan -Dev List" <infinispan-dev@lists.jboss.org> > | > | | >> | Sent: Thursday, June 27, 2013 11:30:53 AM > | > | | >> | Subject: Re: [infinispan-dev] Cachestores performance > | > | | >> | > | > | | >> | I have added FileChannel.force(false) flushes after all write > | > | | >> | operations > | > | | >> | in > | > | | >> | the cache store, and now the comparison is also updated with > these > | > | | >> | values. > | > | | >> | > | > | | >> | Radim > | > | | >> | > | > | | >> | ----- Original Message ----- > | > | | >> | | From: "Radim Vansa" <rva...@redhat.com> > | > | | >> | | To: "infinispan -Dev List" <infinispan-dev@lists.jboss.org> > | > | | >> | | Sent: Thursday, June 27, 2013 8:54:25 AM > | > | | >> | | Subject: Re: [infinispan-dev] Cachestores performance > | > | | >> | | > | > | | >> | | Yep, write-through. LevelDB JAVA used FileChannelTable > | > | | >> | | implementation > | > | | >> | | (-Dleveldb.mmap), because Mmaping is not implemented very well > | > | | >> | | and > | > | | >> | | causes > | > | | >> | | JVM crashes (I believe it's because of calling non-public API > | > | | >> | | via > | > | | >> | | reflection > | > | | >> | | - I've found post from the Oracle JVM guys discouraging the > | > | | >> | | particular > | > | | >> | | trick > | > | | >> | | it uses). After writing the record to the log, it calls > | > | | >> | | FileChannel.force(true), therefore, it should be really on the > | > | | >> | | disc > | > | | >> | | by > | > | | >> | | that > | > | | >> | | moment. > | > | | >> | | I have not looked into the JNI implementation but I expect the > | > | | >> | | same. > | > | | >> | | > | > | | >> | | By the way, I have updated [1] with numbers when running on > more > | > | | >> | | data > | > | | >> | | (2 GB > | > | | >> | | instead of 100 MB). I won't retype it here, so look there. The > | > | | >> | | performance > | > | | >> | | is much lower. > | > | | >> | | I may try also increase JVM heap size and try with a bit more > | > | | >> | | data > | > | | >> | | yet. > | > | | >> | | > | > | | >> | | Radim > | > | | >> | | > | > | | >> | | [1] https://community.jboss.org/wiki/FileCacheStoreRedesign > | > | | >> | | > | > | | >> | | ----- Original Message ----- > | > | | >> | | | From: "Erik Salter" <an1...@hotmail.com> > | > | | >> | | | To: "infinispan -Dev List" <infinispan-dev@lists.jboss.org> > | > | | >> | | | Sent: Wednesday, June 26, 2013 7:40:19 PM > | > | | >> | | | Subject: Re: [infinispan-dev] Cachestores performance > | > | | >> | | | > | > | | >> | | | These were write-through cache stores, right? And with > | > | | >> | | | LevelDB, > | > | | >> | | | this was > | > | | >> | | | through to the database file itself? > | > | | >> | | | > | > | | >> | | | Erik > | > | | >> | | | > | > | | >> | | | -----Original Message----- > | > | | >> | | | From: infinispan-dev-boun...@lists.jboss.org > | > | | >> | | | [mailto:infinispan-dev-boun...@lists.jboss.org] On Behalf Of > | > | | >> | | | Radim > | > | | >> | | | Vansa > | > | | >> | | | Sent: Wednesday, June 26, 2013 11:24 AM > | > | | >> | | | To: infinispan -Dev List > | > | | >> | | | Subject: [infinispan-dev] Cachestores performance > | > | | >> | | | > | > | | >> | | | Hi all, > | > | | >> | | | > | > | | >> | | | according to [1] I've created the comparison of performance > in > | > | | >> | | | stress-tests. > | > | | >> | | | > | > | | >> | | | All setups used local-cache, benchmark was executed via > | > | | >> | | | Radargun > | > | | >> | | | (actually > | > | | >> | | | version not merged into master yet [2]). I've used 4 nodes > | > | | >> | | | just to > | > | | >> | | | get > | > | | >> | | | more > | > | | >> | | | data - each slave was absolutely independent of the others. > | > | | >> | | | > | > | | >> | | | First test was preloading performance - the cache started and > | > | | >> | | | tried > | > | | >> | | | to > | > | | >> | | | load > | > | | >> | | | 1GB of data from harddrive. Without cachestore the startup > | > | | >> | | | takes > | > | | >> | | | about 2 > | > | | >> | | | - > | > | | >> | | | 4 > | > | | >> | | | seconds, average numbers for the cachestores are below: > | > | | >> | | | > | > | | >> | | | FileCacheStore: 9.8 s > | > | | >> | | | KarstenFileCacheStore: 14 s > | > | | >> | | | LevelDB-JAVA impl.: 12.3 s > | > | | >> | | | LevelDB-JNI impl.: 12.9 s > | > | | >> | | | > | > | | >> | | | IMO nothing special, all times seem affordable. We don't > | > | | >> | | | benchmark > | > | | >> | | | exactly > | > | | >> | | | storing the data into the cachestore, here FileCacheStore > took > | > | | >> | | | about > | > | | >> | | | 44 > | > | | >> | | | minutes, while Karsten about 38 seconds, LevelDB-JAVA 4 > | > | | >> | | | minutes > | > | | >> | | | and > | > | | >> | | | LevelDB-JNI 96 seconds. The units are right, it's minutes > | > | | >> | | | compared > | > | | >> | | | to > | > | | >> | | | seconds. But we all know that FileCacheStore is bloody slow. > | > | | >> | | | > | > | | >> | | | Second test is stress test (5 minutes, preceded by 2 minute > | > | | >> | | | warmup) > | > | | >> | | | where > | > | | >> | | | each of 10 threads works on 10k entries with 1kB values (~100 > | > | | >> | | | MB > | > | | >> | | | in > | > | | >> | | | total). > | > | | >> | | | 20 % writes, 80 % reads, as usual. No eviction is configured, > | > | | >> | | | therefore > | > | | >> | | | the > | > | | >> | | | cache-store works as a persistent storage only for case of > | > | | >> | | | crash. > | > | | >> | | | > | > | | >> | | | FileCacheStore: 3.1M reads/s 112 writes/s // on > one > | > | | >> | | | node > | > | | >> | | | the > | > | | >> | | | performance was only 2.96M reads/s 75 writes/s > | > | | >> | | | KarstenFileCacheStore: 9.2M reads/s 226k writes/s // > yikes! > | > | | >> | | | LevelDB-JAVA impl.: 3.9M reads/s 5100 writes/s > | > | | >> | | | LevelDB-JNI impl.: 6.6M reads/s 14k writes/s // on > one > | > | | >> | | | node > | > | | >> | | | the > | > | | >> | | | performance was 3.9M/8.3k - about half of the others > | > | | >> | | | Without cache store: 15.5M reads/s 4.4M writes/s > | > | | >> | | | > | > | | >> | | | Karsten implementation pretty rules here for two reasons. > | > | | >> | | | First of > | > | | >> | | | all, > | > | | >> | | | it > | > | | >> | | | does not flush the data (it calls only > | > | | >> | | | RandomAccessFile.write()). > | > | | >> | | | Other > | > | | >> | | | cheat is that it stores in-memory the keys and offsets of > data > | > | | >> | | | values in > | > | | >> | | | the > | > | | >> | | | database file. Therefore, it's definitely the best choice for > | > | | >> | | | this > | > | | >> | | | scenario, > | > | | >> | | | but it does not allow to scale the cache-store, especially in > | > | | >> | | | cases > | > | | >> | | | where > | > | | >> | | | the keys are big and values small. However, this performance > | > | | >> | | | boost > | > | | >> | | | is > | > | | >> | | | definitely worth checking - I could think of caching the disk > | > | | >> | | | offsets in > | > | | >> | | | memory and querying persistent index only in case of missing > | > | | >> | | | record, > | > | | >> | | | with > | > | | >> | | | part of the persistent index flushed asynchronously (the > index > | > | | >> | | | can > | > | | >> | | | be > | > | | >> | | | always > | > | | >> | | | rebuilt during the preloading for case of crash). > | > | | >> | | | > | > | | >> | | | The third test should have tested the scenario with more data > | > | | >> | | | to > | > | | >> | | | be > | > | | >> | | | stored > | > | | >> | | | than memory - therefore, the stressors operated on 100k > | > | | >> | | | entries > | > | | >> | | | (~100 MB > | > | | >> | | | of > | > | | >> | | | data) but eviction was set to 10k entries (9216 entries ended > | > | | >> | | | up > | > | | >> | | | in > | > | | >> | | | memory > | > | | >> | | | after the test has ended). > | > | | >> | | | > | > | | >> | | | FileCacheStore: 750 reads/s 285 writes/s > | > | | >> | | | // > | > | | >> | | | one > | > | | >> | | | node > | > | | >> | | | had > | > | | >> | | | only 524 reads and 213 writes per second > | > | | >> | | | KarstenFileCacheStore: 458k reads/s 137k writes/s > | > | | >> | | | LevelDB-JAVA impl.: 21k reads/s 9k writes/s > | > | | >> | | | // a > | > | | >> | | | bit > | > | | >> | | | varying > | > | | >> | | | performance > | > | | >> | | | LevelDB-JNI impl.: 13k-46k reads/s 6.6k-15.2k writes/s > | > | | >> | | | // > | > | | >> | | | the > | > | | >> | | | performance varied a lot! > | > | | >> | | | > | > | | >> | | | 100 MB of data is not much, but it takes so long to push it > | > | | >> | | | into > | > | | >> | | | FileCacheStore that I won't use more unless we exclude this > | > | | >> | | | loser > | > | | >> | | | from > | > | | >> | | | the > | > | | >> | | | comparison :) > | > | | >> | | | > | > | | >> | | | Radim > | > | | >> | | | > | > | | >> | | | [1] https://community.jboss.org/wiki/FileCacheStoreRedesign > | > | | >> | | | [2] https://github.com/rvansa/radargun/tree/t_keygen > | > | | >> | | | > | > | | >> | | | ----------------------------------------------------------- > | > | | >> | | | Radim Vansa > | > | | >> | | | Quality Assurance Engineer > | > | | >> | | | JBoss Datagrid > | > | | >> | | | tel. +420532294559 ext. 62559 > | > | | >> | | | > | > | | >> | | | Red Hat Czech, s.r.o. > | > | | >> | | | Brno, Purkyňova 99/71, PSČ 612 45 > | > | | >> | | | Czech Republic > | > | | >> | | | > | > | | >> | | | > | > | | >> | | | _______________________________________________ > | > | | >> | | | infinispan-dev mailing list > | > | | >> | | | infinispan-dev@lists.jboss.org > | > | | >> | | | https://lists.jboss.org/mailman/listinfo/infinispan-dev > | > | | >> | | | > | > | | >> | | | > | > | | >> | | | _______________________________________________ > | > | | >> | | | infinispan-dev mailing list > | > | | >> | | | infinispan-dev@lists.jboss.org > | > | | >> | | | https://lists.jboss.org/mailman/listinfo/infinispan-dev > | > | | >> | | > | > | | >> | | _______________________________________________ > | > | | >> | | infinispan-dev mailing list > | > | | >> | | infinispan-dev@lists.jboss.org > | > | | >> | | https://lists.jboss.org/mailman/listinfo/infinispan-dev > | > | | >> | > | > | | >> | _______________________________________________ > | > | | >> | infinispan-dev mailing list > | > | | >> | infinispan-dev@lists.jboss.org > | > | | >> | https://lists.jboss.org/mailman/listinfo/infinispan-dev > | > | | >> > | > | | >> _______________________________________________ > | > | | >> infinispan-dev mailing list > | > | | >> infinispan-dev@lists.jboss.org > | > | | >> https://lists.jboss.org/mailman/listinfo/infinispan-dev > | > | | > > | > | | > -- > | > | | > Manik Surtani > | > | | > ma...@jboss.org > | > | | > twitter.com/maniksurtani > | > | | > > | > | | > Platform Architect, JBoss Data Grid > | > | | > http://red.ht/data-grid > | > | | > > | > | | > > | > | | > _______________________________________________ > | > | | > infinispan-dev mailing list > | > | | > infinispan-dev@lists.jboss.org > | > | | > https://lists.jboss.org/mailman/listinfo/infinispan-dev > | > | | > | > | | > | > | | -- > | > | | Galder Zamarreño > | > | | gal...@redhat.com > | > | | twitter.com/galderz > | > | | > | > | | Project Lead, Escalante > | > | | http://escalante.io > | > | | > | > | | Engineer, Infinispan > | > | | http://infinispan.org > | > | | > | > | | > | > | | _______________________________________________ > | > | | infinispan-dev mailing list > | > | | infinispan-dev@lists.jboss.org > | > | | https://lists.jboss.org/mailman/listinfo/infinispan-dev > | > | > | > | _______________________________________________ > | > | infinispan-dev mailing list > | > | infinispan-dev@lists.jboss.org > | > | https://lists.jboss.org/mailman/listinfo/infinispan-dev > | > > | > _______________________________________________ > | > infinispan-dev mailing list > | > infinispan-dev@lists.jboss.org > | > https://lists.jboss.org/mailman/listinfo/infinispan-dev > | > | _______________________________________________ > | infinispan-dev mailing list > | infinispan-dev@lists.jboss.org > | https://lists.jboss.org/mailman/listinfo/infinispan-dev > > _______________________________________________ > infinispan-dev mailing list > infinispan-dev@lists.jboss.org > https://lists.jboss.org/mailman/listinfo/infinispan-dev -- Galder Zamarreño gal...@redhat.com twitter.com/galderz Project Lead, Escalante http://escalante.io Engineer, Infinispan http://infinispan.org _______________________________________________ infinispan-dev mailing list infinispan-dev@lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev
