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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>set_dma_reserve</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="The Linux Kernel API" /><link rel="up" href="ch04s03.html" title="More Memory Management Functions" /><link rel="prev" href="re208.html" title="free_area_init_nodes" /><link rel="next" href="re210.html" title="setup_per_zone_wmarks" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>set_dma_reserve</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re208.html">Prev</a> </td><th width="60%" align="center">More Memory Management Functions</th><td width="20%" align="right"> <a accesskey="n" href="re210.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="set_dma_reserve"><a id="API-set-dma-reserve"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>set_dma_reserve —
set the specified number of pages reserved in the first zone
</p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">set_dma_reserve </b>(</code></td><td>unsigned long <var class="pdparam">new_dma_reserve</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id2982308"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>new_dma_reserve</code></em></span></dt><dd><p>
The number of pages to mark reserved
</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id2982335"></a><h2>Description</h2><p>
The per-cpu batchsize and zone watermarks are determined by present_pages.
In the DMA zone, a significant percentage may be consumed by kernel image
and other unfreeable allocations which can skew the watermarks badly. This
function may optionally be used to account for unfreeable pages in the
first zone (e.g., ZONE_DMA). The effect will be lower watermarks and
smaller per-cpu batchsize.
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