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Posted to issues@bookkeeper.apache.org by GitBox <gi...@apache.org> on 2022/01/11 08:29:11 UTC

[GitHub] [bookkeeper] lordcheng10 opened a new issue #2984: journalRemoveFromPageCache default value probably we should set to false

lordcheng10 opened a new issue #2984:
URL: https://github.com/apache/bookkeeper/issues/2984


   **BUG REPORT**
   
   ***Describe the bug***
   The configuration is as follows:
   journalDirectories=/data1/bk-journal
   ledgerDirectories=/data2/bk-data,/data3/bk-data,/data4/bk-data
   data1~data4 are all physical disks.
   Online, we found that when read miss cache(At this time, data2~4 disks will have more reads.), At this time, the flush delay of the joint disk data1 has increased：
   ![image](https://user-images.githubusercontent.com/19296967/148904736-b857ea97-2df2-4206-b4dc-96ba1f42ee9b.png)
   ![image](https://user-images.githubusercontent.com/19296967/148905615-1a83c1b0-9225-4a26-8c41-e770048cdddf.png)
   
   The indicator bookie_journal_JOURNAL_SYNC is mainly for the time-consuming statistics of the method org.apache.bookkeeper.bookie.JournalChannel#forceWrite:
   ![image](https://user-images.githubusercontent.com/19296967/148906642-006db3fd-5aac-4b6e-85f1-30ab9613aee2.png)
   
   Since the journal disk is independent, the bc.forceWrite time-consuming should not be affected. So I suspect that NativeIO.bestEffortRemoveFromPageCache takes time to increase. I'm not particularly sure, but I have a guess: Due to a large amount of disk data being read, the pagecache is affected, which leads to an increase in the time required to call the bestEffortRemoveFromPageCache method here?
   
   So in order to prevent reads from affecting writes, should the default value of journalRemoveFromPageCache be set to false?
   


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[GitHub] [bookkeeper] lordcheng10 commented on issue #2984: journalRemoveFromPageCache default value probably we should set to false

Posted by GitBox <gi...@apache.org>.

lordcheng10 commented on issue #2984:
URL: https://github.com/apache/bookkeeper/issues/2984#issuecomment-1009708672


   @eolivelli @merlimat @pkumar-singh @sijie PTAL,thanks!


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[GitHub] [bookkeeper] lordcheng10 commented on issue #2984: journalRemoveFromPageCache default value probably we should set to false?

Posted by GitBox <gi...@apache.org>.

lordcheng10 commented on issue #2984:
URL: https://github.com/apache/bookkeeper/issues/2984#issuecomment-1009713573


   Also I would like to know what was the purpose of this remove action from page cache in the first place?
   In order to release the page cache and improve read performance?
   @sijie @eolivelli @pkumar-singh @merlimat 


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