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perf tools: Add dso__data_* interface descriptons

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Adding descriptions/explanations for dso__data_* interface
functions.

Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jean Pihet <jean.pihet@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1401892622-30848-10-git-send-email-jolsa@kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
This commit is contained in:
Jiri Olsa
2014-05-07 21:09:59 +02:00
parent a08cae03f4
commit c1f9aa0a61
2 changed files with 97 additions and 0 deletions
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38
tools/perf/util/dso.h
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@@ -149,6 +149,44 @@ char dso__symtab_origin(const struct dso *dso);
int dso__read_binary_type_filename(const struct dso *dso, enum dso_binary_type type,
char *root_dir, char *filename, size_t size);
/*
* The dso__data_* external interface provides following functions:
* dso__data_fd
* dso__data_close
* dso__data_read_offset
* dso__data_read_addr
*
* Please refer to the dso.c object code for each function and
* arguments documentation. Following text tries to explain the
* dso file descriptor caching.
*
* The dso__data* interface allows caching of opened file descriptors
* to speed up the dso data accesses. The idea is to leave the file
* descriptor opened ideally for the whole life of the dso object.
*
* The current usage of the dso__data_* interface is as follows:
*
* Get DSO's fd:
* int fd = dso__data_fd(dso, machine);
* USE 'fd' SOMEHOW
*
* Read DSO's data:
* n = dso__data_read_offset(dso_0, &machine, 0, buf, BUFSIZE);
* n = dso__data_read_addr(dso_0, &machine, 0, buf, BUFSIZE);
*
* Eventually close DSO's fd:
* dso__data_close(dso);
*
* It is not necessary to close the DSO object data file. Each time new
* DSO data file is opened, the limit (RLIMIT_NOFILE/2) is checked. Once
* it is crossed, the oldest opened DSO object is closed.
*
* The dso__delete function calls close_dso function to ensure the
* data file descriptor gets closed/unmapped before the dso object
* is freed.
*
* TODO
*/
int dso__data_fd(struct dso *dso, struct machine *machine);
void dso__data_close(struct dso *dso);