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List: kde-core-devel
Subject: Re: Review Request 120406: ksysguardd: Avoid including IO-wait in CPU load.
From: Thomas_Lübking <thomas.luebking () gmail ! com>
Date: 2014-10-06 13:04:40
Message-ID: 20141006130440.10360.83103 () probe ! kde ! org
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> On Okt. 5, 2014, 10:29 vorm., Milian Wolff wrote:
> > Hmm... there is no way to see the wait time anywhere then, right? I don't see a \
> > way to add individual columns for that. Maybe that should be re-thought for \
> > frameworks. I.e. keep the CPU% like now but add more columns for the individual \
> > cpu/wait times?
>
> Søren Holm wrote:
> That's right. But fact is that IO-wait is not time actually used. It's just a \
> clasification of the idle cpu time.
> Thomas Lübking wrote:
> Notice that it is NOT included in the idle time, though.
> I don't know the code in question, but assume it needs to be added to the idletime \
> somewhere?
> Søren Holm wrote:
> Well - it should not be added.
>
> usertime + nicetime + systemtime + idletime = 1
>
> idletime = true_idle_time + iowait
>
> The true_idle_time is the percentage of time where a process is waiting for IO. \
> During that time the CPU can do other things just as when no process is waiting for \
> IO. IO-wait is AFAIK only used to pinpoint IO-bottlenecks.
> Thomas Lübking wrote:
> If "idletime" already is an aggregation of the /proc/stat idle and iowait, then \
> that's of course not needed.
> > The true_idle_time is the percentage of time where a process is waiting for IO.
>
> iowait should be the time where a cpu waits for I/O - the idle field \
> ("true_idle_time", I assume) is the time where it really doesn't do anything.
> As mentioned, I don't know the code, all I can tell is that fields 4 & 5 are \
> disjunct (you will eg. notice that when monitoring dd: idle drops where iowait \
> raises)
> Søren Holm wrote:
> You are right. The time the CPU is doing nothing is "idle + iowait". So for at \
> quardcore system with a blocking dd running: idletime==75% iowait=25%. From a \
> visualization point of view the idletime is AFAIK not visualized anywhere - only \
> actual CPU-usage is displayed. And IO-wait is for sure not actual CPU-usage since \
> the kernel will be idling there as well.
> Do you know other people that might have a better felling of the ksysguardd code? I \
> for sure have worse insight than you :)
Try adding John Tapsell
- Thomas
-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
https://git.reviewboard.kde.org/r/120406/#review67948
-----------------------------------------------------------
On Sept. 28, 2014, 3:07 nachm., Søren Holm wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/120406/
> -----------------------------------------------------------
>
> (Updated Sept. 28, 2014, 3:07 nachm.)
>
>
> Review request for kde-workspace.
>
>
> Repository: kde-workspace
>
>
> Description
> -------
>
> IO-wait is included in the cpu usage. This is wrong since IO-wait is a part of the \
> idle time. This goes for both total combines CPU-usage and the per CPU usage.
>
> Diffs
> -----
>
> ksysguard/ksysguardd/Linux/stat.c 534a465
>
> Diff: https://git.reviewboard.kde.org/r/120406/diff/
>
>
> Testing
> -------
>
> Fx. running a read from a slow USB-media like this will always end up showing 25% \
> load on my system (I have 4 cores)
> dd if=/dev/sdb of=/dev/null bs=1M
>
> This end up being around 0% with my patch.
>
>
> Thanks,
>
> Søren Holm
>
>
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This is an automatically generated e-mail. To reply, visit:
<a href="https://git.reviewboard.kde.org/r/120406/">https://git.reviewboard.kde.org/r/120406/</a>
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<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <p style="margin-top: 0;">On Oktober 5th, 2014, 10:29 vorm. UTC, <b>Milian \
Wolff</b> wrote:</p> <blockquote style="margin-left: 1em; border-left: 2px solid \
#d0d0d0; padding-left: 10px;"> <pre style="white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">Hmm... there is no way to see the wait time anywhere \
then, right? I don't see a way to add individual columns for that. Maybe that should \
be re-thought for frameworks. I.e. keep the CPU% like now but add more columns for \
the individual cpu/wait times?</p></pre> </blockquote>
<p>On Oktober 5th, 2014, 10:45 vorm. UTC, <b>Søren Holm</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
inherit;">That's right. But fact is that IO-wait is not time actually used. It's just \
a clasification of the idle cpu time.</p></pre> </blockquote>
<p>On Oktober 5th, 2014, 11:04 vorm. UTC, <b>Thomas Lübking</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
inherit;">Notice that it is NOT included in the idle time, though. I don't know the \
code in question, but assume it needs to be added to the idletime \
somewhere?</p></pre> </blockquote>
<p>On Oktober 5th, 2014, 11:29 vorm. UTC, <b>Søren Holm</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">Well \
- it should not be added.</p> <p style="padding: 0;text-rendering: inherit;margin: \
0;line-height: inherit;white-space: inherit;">usertime + nicetime + systemtime + \
idletime = 1</p> <p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">idletime = true_idle_time + iowait</p> <p \
style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
inherit;">The true_idle_time is the percentage of time where a process is waiting for \
IO. During that time the CPU can do other things just as when no process is waiting \
for IO. IO-wait is AFAIK only used to pinpoint IO-bottlenecks.</p></pre> \
</blockquote>
<p>On Oktober 5th, 2014, 11:38 vorm. UTC, <b>Thomas Lübking</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">If \
"idletime" already is an aggregation of the /proc/stat idle and iowait, then that's \
of course not needed.</p> <blockquote style="text-rendering: inherit;padding: 0 0 0 \
1em;border-left: 1px solid #bbb;white-space: normal;margin: 0 0 0 0.5em;line-height: \
inherit;"> <p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">The true_idle_time is the percentage of time where a \
process is waiting for IO.</p> </blockquote>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">iowait should be the time where a cpu waits for I/O - \
the idle field ("true_idle_time", I assume) is the time where it really doesn't do \
anything.</p> <p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">As mentioned, I don't know the code, all I can tell is \
that fields 4 & 5 are disjunct (you will eg. notice that when monitoring dd: idle \
drops where iowait raises)</p></pre> </blockquote>
<p>On Oktober 5th, 2014, 12:11 nachm. UTC, <b>Søren Holm</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">You \
are right. The time the CPU is doing nothing is "idle + iowait". So for at quardcore \
system with a blocking dd running: idletime==75% iowait=25%. From a visualization \
point of view the idletime is AFAIK not visualized anywhere - only actual CPU-usage \
is displayed. And IO-wait is for sure not actual CPU-usage since the kernel will be \
idling there as well.</p> <p style="padding: 0;text-rendering: inherit;margin: \
0;line-height: inherit;white-space: inherit;">Do you know other people that might \
have a better felling of the ksysguardd code? I for sure have worse insight than you \
:)</p></pre> </blockquote>
</blockquote>
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">Try \
adding John Tapsell</p></pre> <br />
<p>- Thomas</p>
<br />
<p>On September 28th, 2014, 3:07 nachm. UTC, Søren Holm wrote:</p>
<table bgcolor="#fefadf" width="100%" cellspacing="0" cellpadding="12" style="border: \
1px #888a85 solid; border-radius: 6px; -moz-border-radius: 6px; \
-webkit-border-radius: 6px;"> <tr>
<td>
<div>Review request for kde-workspace.</div>
<div>By Søren Holm.</div>
<p style="color: grey;"><i>Updated Sept. 28, 2014, 3:07 nachm.</i></p>
<div style="margin-top: 1.5em;">
<b style="color: #575012; font-size: 10pt;">Repository: </b>
kde-workspace
</div>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" \
style="border: 1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">IO-wait is included in the cpu usage. This is wrong \
since IO-wait is a part of the idle time. This goes for both total combines CPU-usage \
and the per CPU usage.</p></pre> </td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: \
1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">Fx. running a read from a slow USB-media like this \
will always end up showing 25% load on my system (I have 4 cores)</p> <p \
style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
inherit;">dd if=/dev/sdb of=/dev/null bs=1M </p> <p style="padding: 0;text-rendering: \
inherit;margin: 0;line-height: inherit;white-space: inherit;">This end up being \
around 0% with my patch.</p></pre> </td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
<ul style="margin-left: 3em; padding-left: 0;">
<li>ksysguard/ksysguardd/Linux/stat.c <span style="color: \
grey">(534a465)</span></li>
</ul>
<p><a href="https://git.reviewboard.kde.org/r/120406/diff/" style="margin-left: \
3em;">View Diff</a></p>
</td>
</tr>
</table>
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