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1111 </para> 1111 </para>
1112 </section> 1112 </section>
1113 1113
1114 <section id='qemu-performance'>
1115 <title>QEMU Performance</title>
1116
1117 <para>
1118 Using QEMU to emulate your hardware can result in speed issues
1119 depending on the target and host architecture mix.
1120 For example, using the <filename>qemux86</filename> image in the
1121 emulator on an Intel-based 32-bit (x86) host machine is fast
1122 because the target and host architectures match.
1123 On the other hand, using the <filename>qemuarm</filename> image
1124 on the same Intel-based host can be slower.
1125 But, you still achieve faithful emulation of ARM-specific issues.
1126 </para>
1127
1128 <para>
1129 To speed things up, the QEMU images support using
1130 <filename>distcc</filename> to call a cross-compiler outside the
1131 emulated system.
1132 If you used <filename>runqemu</filename> to start QEMU, and the
1133 <filename>distccd</filename> application is present on the host
1134 system, any BitBake cross-compiling toolchain available from the
1135 build system is automatically used from within QEMU simply by
1136 calling <filename>distcc</filename>.
1137 You can accomplish this by defining the cross-compiler variable
1138 (e.g. <filename>export CC="distcc"</filename>).
1139 Alternatively, if you are using a suitable SDK image or the
1140 appropriate stand-alone toolchain is present, the toolchain is
1141 also automatically used.
1142 </para>
1143
1144 <note>
1145 Several mechanisms exist that let you connect to the system
1146 running on the QEMU emulator:
1147 <itemizedlist>
1148 <listitem><para>
1149 QEMU provides a framebuffer interface that makes standard
1150 consoles available.
1151 </para></listitem>
1152 <listitem><para>
1153 Generally, headless embedded devices have a serial port.
1154 If so, you can configure the operating system of the
1155 running image to use that port to run a console.
1156 The connection uses standard IP networking.
1157 </para></listitem>
1158 <listitem><para>
1159 SSH servers exist in some QEMU images.
1160 The <filename>core-image-sato</filename> QEMU image has a
1161 Dropbear secure shell (SSH) server that runs with the root
1162 password disabled.
1163 The <filename>core-image-full-cmdline</filename> and
1164 <filename>core-image-lsb</filename> QEMU images
1165 have OpenSSH instead of Dropbear.
1166 Including these SSH servers allow you to use standard
1167 <filename>ssh</filename> and <filename>scp</filename>
1168 commands.
1169 The <filename>core-image-minimal</filename> QEMU image,
1170 however, contains no SSH server.
1171 </para></listitem>
1172 <listitem><para>
1173 You can use a provided, user-space NFS server to boot
1174 the QEMU session using a local copy of the root
1175 filesystem on the host.
1176 In order to make this connection, you must extract a
1177 root filesystem tarball by using the
1178 <filename>runqemu-extract-sdk</filename> command.
1179 After running the command, you must then point the
1180 <filename>runqemu</filename>
1181 script to the extracted directory instead of a root
1182 filesystem image file.
1183 See the
1184 "<ulink url='&YOCTO_DOCS_DEV_URL;#qemu-running-under-a-network-file-system-nfs-server'>Running Under a Network File System (NFS) Server</ulink>"
1185 section in the Yocto Project Development Manual for more
1186 information.
1187 </para></listitem>
1188 </itemizedlist>
1189 </note>
1190 </section>
1191
1114 <section id='qemu-command-line-syntax'> 1192 <section id='qemu-command-line-syntax'>
1115 <title>QEMU Command-Line Syntax</title> 1193 <title>QEMU Command-Line Syntax</title>
1116 1194