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[U-Boot,v2,7/7] Add documentation for bootgraph.pl

Message ID 1315658227-4388-7-git-send-email-amurray@theiet.org
State Deferred
Headers show

Commit Message

Andrew Murray Sept. 10, 2011, 12:37 p.m. UTC
From: Andrew Murray <amurray@mpcdata.com>

Documentation for the CONFIG_BOOT_TRACE option.
Changes for v2:
	- Update documentation for v2 changes

Signed-off-by: Andrew Murray <amurray@theiet.org>
 doc/README.bootgraph |   54 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 54 insertions(+), 0 deletions(-)
 create mode 100644 doc/README.bootgraph
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diff --git a/doc/README.bootgraph b/doc/README.bootgraph
new file mode 100644
index 0000000..cdd8211
--- /dev/null
+++ b/doc/README.bootgraph
@@ -0,0 +1,54 @@ 
+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_boot_trace 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.
+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)
+        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
+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>