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P3 (Plugin Performance Profiler)
[resolved] Variations in Results (4 posts)

  1. Tom Ewer
    Member
    Posted 2 years ago #

    Hello,

    I've just run two concurrent tests, and see 20%-60% swings in individual load times of the same plugin, and an overall 30% swing in total load time. Why is this, and what does it mean for the accuracy and effectiveness of the plugin?

    Cheers,

    Tom Ewer

    http://wordpress.org/extend/plugins/p3-profiler/

  2. Kurt Payne
    Member
    Plugin Contributor

    Posted 2 years ago #

    Hi tomewer,

    If you're on a shared server, other activity on the server can affect your site.

    Even on some virtual private server, this can happen, too. You're guaranteed a minimum of resources, but when more resources are available, you can consume more.

    Server side processes (backups, cron jobs, etc.) can affect measurements.

    And if you have a good bit of traffic on your site, that can affect your measurements, too.

    P3 has a good section in its help about is accuracy:

    How accurate are these results?
    The results have an inherent margin of error because of the nature of the tool and its multi-layered design. The plugin changes the environment to measure it, and that makes it impossible to get completely accurate results.

    It gets really close, though! The "margin of error" on the Advanced Metrics page displays the discrepancy between the measured results (the time for your site's PHP code to completely run) and the expected results (sum of the plugins, core, theme, profile load times) to show you the plugin's accuracy.

    If you want more accurate results, you'll need to resort to a different profiler like xdebug, but this will not break down results by plugin.

    Try taking a few different measurements at different times.

  3. Kurt Payne
    Member
    Plugin Contributor

    Posted 2 years ago #

    One other thing ... plugins can do different things in different runs. For example, a backup plugin may run once and backup the entire site, then it won't run again for a day. The next time you run P3, it will look like your site got faster.

    You should compare the timelines and see which particular URL (or URLs) are the outliers.

  4. Tom Ewer
    Member
    Posted 2 years ago #

    Thanks for getting back to me with such a comprehensive response Kurt - I appreciate it.

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