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perf trace: Associate vfs_getname()'ed pathname with fd returned from 'openat' 

When the vfs_getname() wannabe tracepoint is in place:

  # perf probe -l
    probe:vfs_getname    (on getname_flags:73@acme/git/linux/fs/namei.c with pathname)
  #

'perf trace' will use it to get the pathname when it is copied from
userspace to the kernel, right after syscalls:sys_enter_open, copied
in the 'probe:vfs_getname', stash it somewhere and then, at
syscalls:sys_exit_open time, if the 'open' return is not -1, i.e. a
successfull open syscall, associate that pathname to this return, i.e.
the fd.

We were not doing this for the 'openat' syscall, which would cause 'perf
trace' to fallback to using /proc to get the fd, change it so that we
use what we got from probe:vfs_getname, reducing the 'openat'
beautification process cost, ditching the syscalls performed to read
procfs state and avoiding some possible races in the process.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-xnp44ao3bkb6ejeczxfnjwsh@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo 2018-08-02 10:30:08 -03:00
parent ec2cb7a526
commit 6a648b534d
1 changed files with 8 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
tools/perf/builtin-trace.c
View File

@ -121,7 +121,6 @@ struct trace {
bool force;
bool vfs_getname;
int trace_pgfaults;
int open_id;
};
struct tp_field {
@ -805,12 +804,17 @@ static struct syscall_fmt *syscall_fmt__find(const char *name)
return bsearch(name, syscall_fmts, nmemb, sizeof(struct syscall_fmt), syscall_fmt__cmp);
}
/*
* is_exit: is this "exit" or "exit_group"?
* is_open: is this "open" or "openat"? To associate the fd returned in sys_exit with the pathname in sys_enter.
*/
struct syscall {
struct event_format *tp_format;
int nr_args;
bool is_exit;
bool is_open;
struct format_field *args;
const char *name;
bool is_exit;
struct syscall_fmt *fmt;
struct syscall_arg_fmt *arg_fmt;
};
@ -1299,6 +1303,7 @@ static int trace__read_syscall_info(struct trace *trace, int id)
}
sc->is_exit = !strcmp(name, "exit_group") || !strcmp(name, "exit");
sc->is_open = !strcmp(name, "open") || !strcmp(name, "openat");
return syscall__set_arg_fmts(sc);
}
@ -1722,7 +1727,7 @@ static int trace__sys_exit(struct trace *trace, struct perf_evsel *evsel,
ret = perf_evsel__sc_tp_uint(evsel, ret, sample);
if (id == trace->open_id && ret >= 0 && ttrace->filename.pending_open) {
if (sc->is_open && ret >= 0 && ttrace->filename.pending_open) {
trace__set_fd_pathname(thread, ret, ttrace->filename.name);
ttrace->filename.pending_open = false;
++trace->stats.vfs_getname;
@ -3205,8 +3210,6 @@ int cmd_trace(int argc, const char **argv)
}
}
trace.open_id = syscalltbl__id(trace.sctbl, "open");
err = target__validate(&trace.opts.target);
if (err) {
target__strerror(&trace.opts.target, err, bf, sizeof(bf));