1<html><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 V1.78.1"><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="API-free-area-init-nodes.html" title="free_area_init_nodes"><link rel="next" href="API-setup-per-zone-wmarks.html" title="setup_per_zone_wmarks"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span class="phrase">set_dma_reserve</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-free-area-init-nodes.html">Prev</a>&#160;</td><th width="60%" align="center">More Memory Management Functions</th><td width="20%" align="right">&#160;<a accesskey="n" href="API-setup-per-zone-wmarks.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-set-dma-reserve"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>set_dma_reserve &#8212; 
2     set the specified number of pages reserved in the first zone
3 </p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><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">&#160;</div></div></div><div class="refsect1"><a name="idp1124611820"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>new_dma_reserve</code></em></span></dt><dd><p>
4     The number of pages to mark reserved
5    </p></dd></dl></div></div><div class="refsect1"><a name="idp1124613460"></a><h2>Description</h2><p>
6   The per-cpu batchsize and zone watermarks are determined by present_pages.
7   In the DMA zone, a significant percentage may be consumed by kernel image
8   and other unfreeable allocations which can skew the watermarks badly. This
9   function may optionally be used to account for unfreeable pages in the
10   first zone (e.g., ZONE_DMA). The effect will be lower watermarks and
11   smaller per-cpu batchsize.
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