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https://issues.apache.org/jira/browse/TS-3753?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14636626#comment-14636626
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Pavel Vazharov commented on TS-3753:
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We did two types of tests:
1. Null transform for content coming from remote server.
2. Null transform for content coming from the cache/disk.
We did observe increased CPU iowait and increased serving time only in the
second case.
I'm not sure if this is the same issue, because the TS-2496 doesn't mention if
the served content comes from the cache or from the remote server.
> High CPU iowait with null-transform on a content from the cache.
> ----------------------------------------------------------------
>
> Key: TS-3753
> URL: https://issues.apache.org/jira/browse/TS-3753
> Project: Traffic Server
> Issue Type: Bug
> Components: Plugins, TS API
> Affects Versions: 5.3.0
> Reporter: Pavel Vazharov
> Fix For: 6.1.0
>
> Attachments: null-transform-cache.patch, usi.png
>
>
> Hi,
> I'm trying to calculate some stats doing null-transform on a content served
> from the cache. However, I observed high CPU iowait when doing this. I
> isolated the issue to be related to the case when we do transformation on a
> content served from the cache. Please, see the attached few lines patch which
> when applied to the null-transform plugin causes high CPU iowait. Note also
> that when I tried the original null-transform plugin I didn't observe such
> increased CPU iowait. Please, see also the attached picture where you can see
> the increased CPU iowait (between 15:30 and 16:30 in red) when I started the
> test with null-transform from cache.
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