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From "Ivan Rakov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (IGNITE-5884) Change default pageSize of page memory to 4KB
Date Thu, 31 Aug 2017 13:41:01 GMT

    [ https://issues.apache.org/jira/browse/IGNITE-5884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16148984#comment-16148984
] 

Ivan Rakov commented on IGNITE-5884:
------------------------------------

TC run: https://ci.ignite.apache.org/viewQueued.html?itemId=803028

> Change default pageSize of page memory to 4KB
> ---------------------------------------------
>
>                 Key: IGNITE-5884
>                 URL: https://issues.apache.org/jira/browse/IGNITE-5884
>             Project: Ignite
>          Issue Type: Improvement
>          Components: persistence
>            Reporter: Ivan Rakov
>            Assignee: Ivan Rakov
>            Priority: Critical
>              Labels: usability
>             Fix For: 2.3
>
>         Attachments: CpBenchmark.java, iostat.log, ssdlab.log
>
>
> Checkpoint write speed is suboptimal with default 2K page on most UNIX-driven enviroments
with SSD disk. There are several reasons for this:
> 1) Page size of linux page cache is 4k by default on most kernels (you can check yours
by "getconf PAGE_SIZE" command). With 2k random writes vm.dirty_ratio threshold is reached
two times faster than with 4k random writes.
> 2) Most SSD manufacturers don't expose actual disk page size, but they recommend to write
at least 4k at once. Also, 4k blocks are used during benchmarking SSD random writes. 
> Related question: https://superuser.com/questions/1168014/nvme-ssd-why-is-4k-writing-faster-than-reading
> Article by Emmanuel Goossaert describing why writing less than a page is —Āounterproductive:
http://codecapsule.com/2014/02/12/coding-for-ssds-part-3-pages-blocks-and-the-flash-translation-layer/
> I've prepared a checkpoint emulation benchmark (code and results attached). Run on production-level
hardware (CentOS, 100 GB RAM, total LFS size is 100GB, vm.dirty_ratio=10) showed that checkpointing
with 4k pages is much more efficient than with 2k.
> *Important: backwards compatibility must be ensured with LFS files created with old 2k
default page size.*



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