[jira] [Commented] (HBASE-23887) BlockCache performance improve by reduce eviction rate

["Danil Lipovoy (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-23887?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17155273#comment-17155273 ] 

Danil Lipovoy commented on HBASE-23887:
---------------------------------------

[~bharathv], can I help by some way to merge the feature?

> BlockCache performance improve by reduce eviction rate
> ------------------------------------------------------
>
>                 Key: HBASE-23887
>                 URL: https://issues.apache.org/jira/browse/HBASE-23887
>             Project: HBase
>          Issue Type: Improvement
>          Components: BlockCache, Performance
>            Reporter: Danil Lipovoy
>            Assignee: Danil Lipovoy
>            Priority: Minor
>         Attachments: 1582787018434_rs_metrics.jpg, 1582801838065_rs_metrics_new.png, BC_LongRun.png, BlockCacheEvictionProcess.gif, BlockCacheEvictionProcess.gif, cmp.png, evict_BC100_vs_BC23.png, eviction_100p.png, eviction_100p.png, eviction_100p.png, gc_100p.png, graph.png, image-2020-06-07-08-11-11-929.png, image-2020-06-07-08-19-00-922.png, image-2020-06-07-12-07-24-903.png, image-2020-06-07-12-07-30-307.png, image-2020-06-08-17-38-45-159.png, image-2020-06-08-17-38-52-579.png, image-2020-06-08-18-35-48-366.png, image-2020-06-14-20-51-11-905.png, image-2020-06-22-05-57-45-578.png, ratio.png, ratio2.png, read_requests_100pBC_vs_23pBC.png, requests_100p.png, requests_100p.png, requests_new2_100p.png, requests_new_100p.png, scan.png, scan_and_gets.png, scan_and_gets2.png, wave.png
>
>
> Hi!
> I first time here, correct me please if something wrong.
> All latest information is here:
> [https://docs.google.com/document/d/1X8jVnK_3lp9ibpX6lnISf_He-6xrHZL0jQQ7hoTV0-g/edit?usp=sharing]
> I want propose how to improve performance when data in HFiles much more than BlockChache (usual story in BigData). The idea - caching only part of DATA blocks. It is good becouse LruBlockCache starts to work and save huge amount of GC.
> Sometimes we have more data than can fit into BlockCache and it is cause a high rate of evictions. In this case we can skip cache a block N and insted cache the N+1th block. Anyway we would evict N block quite soon and that why that skipping good for performance.
> ---
> Some information below isn't  actual
> ---
>  
>  
> Example:
> Imagine we have little cache, just can fit only 1 block and we are trying to read 3 blocks with offsets:
>  124
>  198
>  223
> Current way - we put the block 124, then put 198, evict 124, put 223, evict 198. A lot of work (5 actions).
> With the feature - last few digits evenly distributed from 0 to 99. When we divide by modulus we got:
>  124 -> 24
>  198 -> 98
>  223 -> 23
> It helps to sort them. Some part, for example below 50 (if we set *hbase.lru.cache.data.block.percent* = 50) go into the cache. And skip others. It means we will not try to handle the block 198 and save CPU for other job. In the result - we put block 124, then put 223, evict 124 (3 actions).
> See the picture in attachment with test below. Requests per second is higher, GC is lower.
>  
>  The key point of the code:
>  Added the parameter: *hbase.lru.cache.data.block.percent* which by default = 100
>   
>  But if we set it 1-99, then will work the next logic:
>   
>   
> {code:java}
> public void cacheBlock(BlockCacheKey cacheKey, Cacheable buf, boolean inMemory) {   
>   if (cacheDataBlockPercent != 100 && buf.getBlockType().isData())      
>     if (cacheKey.getOffset() % 100 >= cacheDataBlockPercent) 
>       return;    
> ... 
> // the same code as usual
> }
> {code}
>  
> Other parameters help to control when this logic will be enabled. It means it will work only while heavy reading going on.
> hbase.lru.cache.heavy.eviction.count.limit - set how many times have to run eviction process that start to avoid of putting data to BlockCache
>  hbase.lru.cache.heavy.eviction.bytes.size.limit - set how many bytes have to evicted each time that start to avoid of putting data to BlockCache
> By default: if 10 times (100 secunds) evicted more than 10 MB (each time) then we start to skip 50% of data blocks.
>  When heavy evitions process end then new logic off and will put into BlockCache all blocks again.
>   
> Descriptions of the test:
> 4 nodes E5-2698 v4 @ 2.20GHz, 700 Gb Mem.
> 4 RegionServers
> 4 tables by 64 regions by 1.88 Gb data in each = 600 Gb total (only FAST_DIFF)
> Total BlockCache Size = 48 Gb (8 % of data in HFiles)
> Random read in 20 threads
>  
> I am going to make Pull Request, hope it is right way to make some contribution in this cool product.  
>  



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