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From "Ariel Weisberg (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-13031) Speed-up start-up sequence by avoiding un-needed flushes
Date Fri, 23 Dec 2016 16:46:58 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-13031?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Ariel Weisberg updated CASSANDRA-13031:
---------------------------------------
    Attachment: debug_130131_2.diff

I only ask because I added the timing to try and measure myself and didn't see a big impact.
I am just trying to make sure it has an impact on some use case before I +1. Most SSDs do
pretty fast syncs and most disks on servers also do pretty fast syncs because they are fronted
by a battery backed write cache.

Here are the measurements I just took on my MBP (which yes has a very fast SSD, and does OS
X respect write barriers?). debug=true is supposed to be without these changes and debug=false
is supposed to be with these changes.

||debug=true|debug=false||
|5.144|5.007|
|4.466|4.090|
|4.211|3.922|
|4.040|4.053|

There is an effect where repeated runs after compilation are faster.

> Speed-up start-up sequence by avoiding un-needed flushes
> --------------------------------------------------------
>
>                 Key: CASSANDRA-13031
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13031
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Corentin Chary
>            Priority: Minor
>             Fix For: 3.x
>
>         Attachments: 0001-Avoid-un-needed-system-flushes-on-startup.patch, debug_130131.diff,
debug_130131_2.diff
>
>
> Similar to CASSANDRA-12969, do a conditional update for all functions
>     with a forced blocking flush to avoid slowed-down boot sequences. The
>     small performance hit of doing a read is always smaller than the one
>     associated with a fsync().



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