[GitHub] [bookkeeper] hangc0276 commented on pull request #3260: Optimize write cache:①Two write caches become multi-cache blocks;②All data directories share write cache resources;

[GitBox <gi...@apache.org>]

hangc0276 commented on PR #3260:
URL: https://github.com/apache/bookkeeper/pull/3260#issuecomment-1123924412

   Sharing the write cache pool with all ledger disks may cause competition for write cache resources, and eventually cause some ledger writes starve to death because they cannot get the write cache.
   
   Suppose there are 3 ledgers, corresponding to 3 disks data1, data2 and data3, and the write cache pool size is 6. The traffic on data1 is relatively high, and the number of applied write caches will be skewed toward data1. If a large number of disk reads occur in data1 at a certain time, the write performance of data1 decreases, causing the write cache of pending flush to increase. The write cache pool is exhausted, and other normal disks data2 and data3 will wait because the write cache cannot be obtained.
   
   Maybe we need a proposal and send to the dev mail list to discuss.
   
   @merlimat  @eolivelli @dlg99  Please help take a look, thanks.


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