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List: kde-frameworks-devel
Subject: Re: Review Request 126894: Refactor the listjobtest to allow listing of multile paths.
From: Frank Reininghaus <frank78ac () googlemail ! com>
Date: 2016-01-27 6:33:05
Message-ID: 20160127063305.17778.62901 () mimi ! kde ! org
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https://git.reviewboard.kde.org/r/126894/#review91634
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Thanks Milian for looking at this test. I implemented it quite some time ago as a \
quick hack that allows to see how changes in the internal data structures of UDSEntry \
affect the performance and especially the memory usage of KIO::ListJob (which is what \
applications typically use to obtain UDSEntries). I did it in Qt4 times, when one \
could not use lambdas in connections. It's great to see the test simplified and \
extended now :-)
I have two remarks:
* Appending the listed entries to a list was intentional. If they are discarded \
immediately, then their memory is freed, and it is not possible to see how much \
memory the entries would consume in an application that lists one or more paths. I \
see that this original intention of the test is not obvious at all though. I should \
have added a comment - sorry about that!
* The `std::cin.ignore()` was also intentional. It allows to investigate the memory \
usage with htop, ps, or other tools while the process is still running. I know that \
one could also use Valgrind/Massif+massif-visualizer to get a detailed memory usage \
report (which also contains detailed information about where and when memory was \
allocated), but this has the disadvantage that the bookkeeping overhead of the memory \
allocator is not included (or at least it was not last time I checked). The massif \
method would tell you that an application that allocates 100 MiB in a single block \
uses more memory than an application that allocates 10 million blocks of 8 bytes \
each, but this is not true because some bookkeeping overhead is added to each \
allocation. Each allocation takes at least 32 bytes of memory when using GCC+glibc on \
a 64-bit system. But I guess that there must be a better way than the `cin.ignore()` \
hack to easily get the real memory usage.
- Frank Reininghaus
On Jan. 26, 2016, 3:34 nachm., Milian Wolff wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/126894/
> -----------------------------------------------------------
>
> (Updated Jan. 26, 2016, 3:34 nachm.)
>
>
> Review request for KDE Frameworks and David Faure.
>
>
> Repository: kio
>
>
> Description
> -------
>
> With this change it is now possible to list multiple paths
> as defined via the command line.
>
> While at it, I refactored the code to clean it up:
>
> - rely on QEventLoopLocker to quit the application once all jobs
> have finished
> - use a lambda to count the listed entries
> - don't append to a KIO::UDSEntryList to cound the listed entries
>
>
> Diffs
> -----
>
> tests/listjobtest.cpp 702b09950734894a9f82746d58071225419b4e3f
>
> Diff: https://git.reviewboard.kde.org/r/126894/diff/
>
>
> Testing
> -------
>
>
> Thanks,
>
> Milian Wolff
>
>
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This is an automatically generated e-mail. To reply, visit:
<a href="https://git.reviewboard.kde.org/r/126894/">https://git.reviewboard.kde.org/r/126894/</a>
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<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;">Thanks Milian for looking at this test. I implemented it quite some time \
ago as a quick hack that allows to see how changes in the internal data structures of \
UDSEntry affect the performance and especially the memory usage of KIO::ListJob \
(which is what applications typically use to obtain UDSEntries). I did it in Qt4 \
times, when one could not use lambdas in connections. It's great to see the test \
simplified and extended now :-)</p> <p style="padding: 0;text-rendering: \
inherit;margin: 0;line-height: inherit;white-space: inherit;">I have two remarks:</p> \
<ul style="padding: 0;text-rendering: inherit;margin: 0 0 0 1em;line-height: \
inherit;white-space: normal;"> <li style="padding: 0;text-rendering: inherit;margin: \
0;line-height: inherit;white-space: normal;">Appending the listed entries to a list \
was intentional. If they are discarded immediately, then their memory is freed, and \
it is not possible to see how much memory the entries would consume in an application \
that lists one or more paths. I see that this original intention of the test is not \
obvious at all though. I should have added a comment - sorry about that!</li> <li \
style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
normal;">The <code style="text-rendering: inherit;color: #4444cc;padding: \
0;white-space: normal;margin: 0;line-height: inherit;">std::cin.ignore()</code> was \
also intentional. It allows to investigate the memory usage with htop, ps, or other \
tools while the process is still running. I know that one could also use \
Valgrind/Massif+massif-visualizer to get a detailed memory usage report (which also \
contains detailed information about where and when memory was allocated), but this \
has the disadvantage that the bookkeeping overhead of the memory allocator is not \
included (or at least it was not last time I checked). The massif method would tell \
you that an application that allocates 100 MiB in a single block uses more memory \
than an application that allocates 10 million blocks of 8 bytes each, but this is not \
true because some bookkeeping overhead is added to each allocation. Each allocation \
takes at least 32 bytes of memory when using GCC+glibc on a 64-bit system. But I \
guess that there must be a better way than the <code style="text-rendering: \
inherit;color: #4444cc;padding: 0;white-space: normal;margin: 0;line-height: \
inherit;">cin.ignore()</code> hack to easily get the real memory usage.</li> \
</ul></pre> <br />
<p>- Frank Reininghaus</p>
<br />
<p>On Januar 26th, 2016, 3:34 nachm. UTC, Milian Wolff wrote:</p>
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<div>Review request for KDE Frameworks and David Faure.</div>
<div>By Milian Wolff.</div>
<p style="color: grey;"><i>Updated Jan. 26, 2016, 3:34 nachm.</i></p>
<div style="margin-top: 1.5em;">
<b style="color: #575012; font-size: 10pt;">Repository: </b>
kio
</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;">With this change it is now possible to list multiple paths as defined \
via the command line.
While at it, I refactored the code to clean it up:
- rely on QEventLoopLocker to quit the application once all jobs
have finished
- use a lambda to count the listed entries
- don't append to a KIO::UDSEntryList to cound the listed entries</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>tests/listjobtest.cpp <span style="color: \
grey">(702b09950734894a9f82746d58071225419b4e3f)</span></li>
</ul>
<p><a href="https://git.reviewboard.kde.org/r/126894/diff/" style="margin-left: \
3em;">View Diff</a></p>
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