<!DOCTYPE html>
<html lang='en'>
<head>
<title>gnu: python-qemu-qmp: Move to pyproject-build-system. - guix - Wojtek's customized Guix</title>
<meta name='generator' content='cgit v1.2.3'/>
<meta name='robots' content='noindex, nofollow'/>
<link rel='stylesheet' type='text/css' href='/cgit-static/cgit.css'/>
<link rel='stylesheet' type='text/css' href='/cgit-static/better-cgit-markdown-heading-color.css'/>
<link rel='shortcut icon' href='/cgit-static/favicon.ico'/>
<link rel='alternate' title='Atom feed' href='https://git.koszko.org/guix/atom/gnu/tests/data?h=koszko' type='application/atom+xml'/>
</head>
<body>
<div id='cgit'><table id='header'>
<tr>
<td class='logo' rowspan='2'><a href='/'><img src='https://git.koszko.org/cgit-static/cgit.png' alt='cgit logo'/></a></td>
<td class='main'><a href='/'>index</a> : <a href='/guix/'>guix</a></td><td class='form'><form method='get'>
<input type='hidden' name='id' value='d41e9ce19478143883c2c81d9d1bbac6d4e6760a'/><select name='h' onchange='this.form.submit();'>
<option value='koszko' selected='selected'>koszko</option>
<option value='koszko-scripts'>koszko-scripts</option>
</select> <input type='submit' value='switch'/></form></td></tr>
<tr><td class='sub'>Wojtek's customized Guix</td><td class='sub right'>it' value='switch'/></form></td></tr>
<tr><td class='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
<table class='tabs'><tr><td>
<a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=e451612602c5ae8bca1e56492bbfa7b2fe434cbd'>refs</a><a href='/guix/log/gnu/packages/patches/ghc-8.0-fall-back-to-madv_dontneed.patch'>log</a><a class='active' href='/guix/tree/gnu/packages/patches/ghc-8.0-fall-back-to-madv_dontneed.patch?id=e451612602c5ae8bca1e56492bbfa7b2fe434cbd'>tree</a><a href='/guix/commit/gnu/packages/patches/ghc-8.0-fall-back-to-madv_dontneed.patch?id=e451612602c5ae8bca1e56492bbfa7b2fe434cbd'>commit</a><a href='/guix/diff/gnu/packages/patches/ghc-8.0-fall-back-to-madv_dontneed.patch?id=e451612602c5ae8bca1e56492bbfa7b2fe434cbd'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/packages/patches/ghc-8.0-fall-back-to-madv_dontneed.patch'>
<input type='hidden' name='id' value='e451612602c5ae8bca1e56492bbfa7b2fe434cbd'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/tree/?id=e451612602c5ae8bca1e56492bbfa7b2fe434cbd'>root</a>/<a href='/guix/tree/gnu?id=e451612602c5ae8bca1e56492bbfa7b2fe434cbd'>gnu</a>/<a href='/guix/tree/gnu/packages?id=e451612602c5ae8bca1e56492bbfa7b2fe434cbd'>packages</a>/<a href='/guix/tree/gnu/packages/patches?id=e451612602c5ae8bca1e56492bbfa7b2fe434cbd'>patches</a>/<a href='/guix/tree/gnu/packages/patches/ghc-8.0-fall-back-to-madv_dontneed.patch?id=e451612602c5ae8bca1e56492bbfa7b2fe434cbd'>ghc-8.0-fall-back-to-madv_dontneed.patch</a></div><div class='content'>blob: 1838c5bd3529ad22f5ff1d8ed75d5504b6f0cad1 (<a href='/guix/about/gnu/packages/patches/ghc-8.0-fall-back-to-madv_dontneed.patch?id=e451612602c5ae8bca1e56492bbfa7b2fe434cbd'>about</a>) (<a href='/guix/plain/gnu/packages/patches/ghc-8.0-fall-back-to-madv_dontneed.patch?id=e451612602c5ae8bca1e56492bbfa7b2fe434cbd'>plain</a>)
<table summary='blob content' class='blob'>
<tr><td class='linenumbers'><pre><a id='n1' href='#n1'>1</a>
<a id='n2' href='#n2'>2</a>
<a id='n3' href='#n3'>3</a>
<a id='n4' href='#n4'>4</a>
<a id='n5' href='#n5'>5</a>
<a id='n6' href='#n6'>6</a>
<a id='n7' href='#n7'>7</a>
<a id='n8' href='#n8'>8</a>
<a id='n9' href='#n9'>9</a>
<a id='n10' href='#n10'>10</a>
<a id='n11' href='#n11'>11</a>
<a id='n12' href='#n12'>12</a>
<a id='n13' href='#n13'>13</a>
<a id='n14' href='#n14'>14</a>
<a id='n15' href='#n15'>15</a>
<a id='n16' href='#n16'>16</a>
<a id='n17' href='#n17'>17</a>
<a id='n18' href='#n18'>18</a>
<a id='n19' href='#n19'>19</a>
<a id='n20' href='#n20'>20</a>
<a id='n21' href='#n21'>21</a>
<a id='n22' href='#n22'>22</a>
<a id='n23' href='#n23'>23</a>
<a id='n24' href='#n24'>24</a>
<a id='n25' href='#n25'>25</a>
<a id='n26' href='#n26'>26</a>
<a id='n27' href='#n27'>27</a>
<a id='n28' href='#n28'>28</a>
<a id='n29' href='#n29'>29</a>
<a id='n30' href='#n30'>30</a>
<a id='n31' href='#n31'>31</a>
<a id='n32' href='#n32'>32</a>
<a id='n33' href='#n33'>33</a>
<a id='n34' href='#n34'>34</a>
<a id='n35' href='#n35'>35</a>
<a id='n36' href='#n36'>36</a>
<a id='n37' href='#n37'>37</a>
<a id='n38' href='#n38'>38</a>
<a id='n39' href='#n39'>39</a>
<a id='n40' href='#n40'>40</a>
<a id='n41' href='#n41'>41</a>
<a id='n42' href='#n42'>42</a>
<a id='n43' href='#n43'>43</a>
<a id='n44' href='#n44'>44</a>
<a id='n45' href='#n45'>45</a>
<a id='n46' href='#n46'>46</a>
<a id='n47' href='#n47'>47</a>
<a id='n48' href='#n48'>48</a>
<a id='n49' href='#n49'>49</a>
<a id='n50' href='#n50'>50</a>
<a id='n51' href='#n51'>51</a>
<a id='n52' href='#n52'>52</a>
<a id='n53' href='#n53'>53</a>
<a id='n54' href='#n54'>54</a>
<a id='n55' href='#n55'>55</a>
<a id='n56' href='#n56'>56</a>
<a id='n57' href='#n57'>57</a>
<a id='n58' href='#n58'>58</a>
<a id='n59' href='#n59'>59</a>
<a id='n60' href='#n60'>60</a>
<a id='n61' href='#n61'>61</a>
</pre></td>
<td class='lines'><pre><code>ghc runtime by default (otherwise depending on a "configure" option)
does memory allocation on their own by first mmapping a 1 TB range of
memory into the process and then parceling out chunks from it.

If one of the chunks is not needed, the kernel needs to be informed -
otherwise the system would quickly run out of available RAM.

ghc does that via madvise(2).

There are two options when doing this informing:

MADV_FREE - Means "I don't need this range or the data in it any more". 
Kernel promises to fail later accesses to it.

MADV_DONTNEED - Means "I don't need this range right now - and I don't
need the data in it anymore". Kernel promises to make later accesses to
it succeed (if necessary by providing a new page initialized with zeroes).

MADV_FREE was introduced in Linux 4.5.
glibc 2.25 and later always define MADV_FREE.

Unpatched ghc 8.0.2 will use either MADV_FREE or MADV_DONTNEED, determined
at ghc compile time.  Which of them will actually succeed is determined
by the Linux kernel at run time.

This patch makes ghc try MADV_FREE.  If it doesn't work, it falls back to
MADV_DONTNEED.

The end result is that ghc programs free their memory with Linux &lt; 4.5 again.

See https://git.haskell.org/ghc.git/commitdiff/6576bf83cdf4eac05eb88a24aa934a736c91e3da for more information.
--- a/rts/posix/OSMem.c
+++ b/rts/posix/OSMem.c
@@ -541,11 +541,24 @@ void osDecommitMemory(void *at, W_ size)
 
 #ifdef MADV_FREE
     // Try MADV_FREE first, FreeBSD has both and MADV_DONTNEED
-    // just swaps memory out
+    // just swaps memory out. Linux &gt;= 4.5 has both DONTNEED and FREE; either
+    // will work as they both allow the system to free anonymous pages.
+    // It is important that we try both methods as the kernel which we were
+    // built on may differ from the kernel we are now running on.
     r = madvise(at, size, MADV_FREE);
-#else
-    r = madvise(at, size, MADV_DONTNEED);
+    if(r &lt; 0) {
+        if (errno == EINVAL) {
+            // Perhaps the system doesn't support MADV_FREE; fall-through and
+            // try MADV_DONTNEED.
+        } else {
+            sysErrorBelch("unable to decommit memory");
+        }
+    } else {
+        return;
+    }
 #endif
+
+    r = madvise(at, size, MADV_DONTNEED);
     if(r &lt; 0)
         sysErrorBelch("unable to decommit memory");
 }
</code></pre></td></tr></table>
</div> <!-- class=content -->
                         <div class=footer>generated by
                             <a href="https://git.zx2c4.com/cgit/about/">
                                 cgit
                             </a>
                         </div>
                        </div> <!-- id=cgit -->
</body>
</html>
