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Posted to issues@ignite.apache.org by "Vladimir Ozerov (JIRA)" <ji...@apache.org> on 2017/09/28 06:55:01 UTC
[jira] [Updated] (IGNITE-5884) Change default pageSize of page
memory to 4KB
[ https://issues.apache.org/jira/browse/IGNITE-5884?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Vladimir Ozerov updated IGNITE-5884:
------------------------------------
Labels: important usability (was: usability)
> 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: important, 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 сounterproductive: 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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