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Subject[PATCH 07/14] perf tools: Cache dso data file descriptor
Date
Caching dso data file descriptors to avoid expensive re-opens
especially during DWARF unwind.

We keep dsos data file descriptors open until their count reaches
the half of the current fd open limit (RLIMIT_NOFILE). In this case
we close file descriptor of the first opened dso object.

We've got overall speedup (~27% for my workload) of report:
'perf report --stdio -i perf-test.data' (3 runs)
(perf-test.data size was around 12GB)

current code:
545,640,944,228 cycles ( +- 0.53% )
785,255,798,320 instructions ( +- 0.03% )

366.340910010 seconds time elapsed ( +- 3.65% )

after change:
435,895,036,114 cycles ( +- 0.26% )
636,790,271,176 instructions ( +- 0.04% )

266.481463387 seconds time elapsed ( +- 0.13% )

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/1401892622-30848-7-git-send-email-jolsa@kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/perf/util/dso.c | 61 ++++++++++++++++++++++++++++++++++++--
tools/perf/util/unwind-libunwind.c | 2 --
2 files changed, 59 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 76e5c13..fbf6cc9 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -1,4 +1,6 @@
#include <asm/bug.h>
+#include <sys/time.h>
+#include <sys/resource.h>
#include "symbol.h"
#include "dso.h"
#include "machine.h"
@@ -180,12 +182,20 @@ static int __open_dso(struct dso *dso, struct machine *machine)
return fd;
}

+static void check_data_close(void);
+
static int open_dso(struct dso *dso, struct machine *machine)
{
int fd = __open_dso(dso, machine);

- if (fd > 0)
+ if (fd > 0) {
dso__list_add(dso);
+ /*
+ * Check if we crossed the allowed number
+ * of opened DSOs and close one if needed.
+ */
+ check_data_close();
+ }

return fd;
}
@@ -204,6 +214,54 @@ static void close_dso(struct dso *dso)
close_data_fd(dso);
}

+static void close_first_dso(void)
+{
+ struct dso *dso;
+
+ dso = list_first_entry(&dso__data_open, struct dso, data.open_entry);
+ close_dso(dso);
+}
+
+static rlim_t get_fd_limit(void)
+{
+ struct rlimit l;
+ rlim_t limit = 0;
+
+ /* Allow half of the current open fd limit. */
+ if (getrlimit(RLIMIT_NOFILE, &l) == 0) {
+ if (l.rlim_cur == RLIM_INFINITY)
+ limit = l.rlim_cur;
+ else
+ limit = l.rlim_cur / 2;
+ } else {
+ pr_err("failed to get fd limit\n");
+ limit = 1;
+ }
+
+ return limit;
+}
+
+static bool may_cache_fd(void)
+{
+ static rlim_t limit;
+
+ if (!limit)
+ limit = get_fd_limit();
+
+ if (limit == RLIM_INFINITY)
+ return true;
+
+ return limit > (rlim_t) dso__data_open_cnt;
+}
+
+static void check_data_close(void)
+{
+ bool cache_fd = may_cache_fd();
+
+ if (!cache_fd)
+ close_first_dso();
+}
+
void dso__data_close(struct dso *dso)
{
close_dso(dso);
@@ -356,7 +414,6 @@ dso_cache__read(struct dso *dso, struct machine *machine,
if (ret <= 0)
free(cache);

- dso__data_close(dso);
return ret;
}

diff --git a/tools/perf/util/unwind-libunwind.c b/tools/perf/util/unwind-libunwind.c
index 4f8dd9e..25578b9 100644
--- a/tools/perf/util/unwind-libunwind.c
+++ b/tools/perf/util/unwind-libunwind.c
@@ -250,7 +250,6 @@ static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,

/* Check the .eh_frame section for unwinding info */
offset = elf_section_offset(fd, ".eh_frame_hdr");
- dso__data_close(dso);

if (offset)
ret = unwind_spec_ehframe(dso, machine, offset,
@@ -271,7 +270,6 @@ static int read_unwind_spec_debug_frame(struct dso *dso,

/* Check the .debug_frame section for unwinding info */
*offset = elf_section_offset(fd, ".debug_frame");
- dso__data_close(dso);

if (*offset)
return 0;
--
1.8.3.1


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