1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>blk_limits_io_opt</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="blkdev.html" title="Chapter&#160;14.&#160;Block Devices"><link rel="prev" href="API-blk-queue-io-min.html" title="blk_queue_io_min"><link rel="next" href="API-blk-queue-io-opt.html" title="blk_queue_io_opt"></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">blk_limits_io_opt</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-blk-queue-io-min.html">Prev</a>&#160;</td><th width="60%" align="center">Chapter&#160;14.&#160;Block Devices</th><td width="20%" align="right">&#160;<a accesskey="n" href="API-blk-queue-io-opt.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-blk-limits-io-opt"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>blk_limits_io_opt &#8212; 
2     set optimal request size for a device
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">blk_limits_io_opt </b>(</code></td><td>struct queue_limits * <var class="pdparam">limits</var>, </td></tr><tr><td>&#160;</td><td>unsigned int <var class="pdparam">opt</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1128505900"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>limits</code></em></span></dt><dd><p>
4     the queue limits
5    </p></dd><dt><span class="term"><em class="parameter"><code>opt</code></em></span></dt><dd><p>
6     smallest I/O size in bytes
7    </p></dd></dl></div></div><div class="refsect1"><a name="idp1128508524"></a><h2>Description</h2><p>
8   Storage devices may report an optimal I/O size, which is the
9   device's preferred unit for sustained I/O.  This is rarely reported
10   for disk drives.  For RAID arrays it is usually the stripe width or
11   the internal track size.  A properly aligned multiple of
12   optimal_io_size is the preferred request size for workloads where
13   sustained throughput is desired.
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