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From "Ivan Rakov (JIRA)" <j...@apache.org>
Subject [jira] [Created] (IGNITE-5884) Change default pageSize of page memory to 4KB
Date Mon, 31 Jul 2017 14:50:00 GMT
Ivan Rakov created IGNITE-5884:
----------------------------------

             Summary: 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
             Fix For: 2.2


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 reveal 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
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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