From: Andrew Murray amurray@mpcdata.com
Documentation for the CONFIG_BOOT_TRACE option.
Signed-off-by: Andrew Murray amurray@theiet.org --- doc/README.bootgraph | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 57 insertions(+), 0 deletions(-) create mode 100644 doc/README.bootgraph
diff --git a/doc/README.bootgraph b/doc/README.bootgraph new file mode 100644 index 0000000..af8d9e4 --- /dev/null +++ b/doc/README.bootgraph @@ -0,0 +1,57 @@ +Bootgraph Instrumentation +------------------------- + +The CONFIG_BOOT_TRACE configuration option can be defined to output extensive +instrumentation to assist in boot time reduction. The tools/bootgraph.pl script +can utilise this instrumentation to generate an SVG graph showing where UBoot +spends its time. + +When enabled all printf output is prefixed with timing information similar +to the Linux kernel's CONFIG_PRINTK_TIME option. This allows you to measure the +interval between operations which is useful for identifying long delays during +UBoot operation. For example: + +[ 3.133000] ## Booting kernel from Legacy Image at 82000000 ... +[ 3.139000] Image Name: Angstrom/2.6.32/beagleboard + +When enabled additional console output will be generated - this output includes +the addresses of executed commands and instrumented functions. For example: + +[ 2.456000] initcall 0x9ff86814 returned +[ 2.460000] calling 0x9ff7c338 +[ 2.590000] initcall 0x9ff7c338 returned +[ 2.594000] calling 0x9ff864ac + +At present executed commands are only displayed when the HUSH parser +(CONFIG_SYS_HUSH_PARSER) is not being used. + +Functions such as initialisation code can be instrumented by using the +DO_INITCALLXXX macros found in include/common.h (see arch/arm/lib/board.c) for +examples). For example: + +@@ -508,7 +518,7 @@ void board_init_r (gd_t *id, ulong dest_addr) + + #ifdef CONFIG_GENERIC_MMC + puts("MMC: "); +- mmc_initialize(bd); ++ DO_INITCALL(mmc_initialize, bd); + #endif + +For functions that do not return such as do_bootm function, the DO_INITCALL_END +macro can be used to mark the latest point of the function. + +When CONFIG_BOOT_TIME is not defined the DO_INITCALLXXX macros continue to call +the intended function and should not add overhead. + +An SVG graph can be generated which allows for the visualisation of UBoot boot +time by using the tools/bootgraph.pl script. This script has been ported from +the Linux kernel (scripts/bootgraph.pl) and is used in a similar way. For +example: + +cat console_output | perl ./tools/bootgraph.pl > graph.svg + +Assuming console_output is a file containing the console output of UBoot with +CONFIG_BOOT_TRACE enabled - the graph.svg file should provide a graphical +representation of boot time with resolved function addresses. + +Andrew Murray amurray@theiet.org