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authorNelson Elhage <nelhage@nelhage.com>2011-12-19 08:39:32 -0500
committerArnaldo Carvalho de Melo <acme@redhat.com>2011-12-23 16:53:58 -0200
commit41d0d933494ce10eb77758a1168b08e317c42e8e (patch)
treef907773714846b5b5cf85b4f450bb6fe07b168d4 /tools
parent18e6093904abfd51671ff5846c2fdaba9ebbf21b (diff)
downloadlinux-linaro-stable-41d0d933494ce10eb77758a1168b08e317c42e8e.tar.gz
perf: builtin-record: Document and check that mmap_pages must be a power of two.
Now that we automatically point users at it, let's provide them some guidance so that they hopefully don't just get mysterious EINVAL's from the kernel. Cc: Ingo Molnar <mingo@elte.hu> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1324301972-22740-4-git-send-email-nelhage@nelhage.com Signed-off-by: Nelson Elhage <nelhage@nelhage.com> [ committer note: Made it work after 50a682c ] Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools')
-rw-r--r--tools/perf/Documentation/perf-record.txt2
-rw-r--r--tools/perf/builtin-record.c3
-rw-r--r--tools/perf/util/evlist.c2
-rw-r--r--tools/perf/util/util.h11
4 files changed, 17 insertions, 1 deletions
diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 5a520f825295..2937f7e14bb7 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -89,7 +89,7 @@ OPTIONS
-m::
--mmap-pages=::
- Number of mmap data pages.
+ Number of mmap data pages. Must be a power of two.
-g::
--call-graph::
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 56bb4476e3ba..e873ae2dd54c 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -279,6 +279,9 @@ try_again:
"/proc/sys/kernel/perf_event_mlock_kb,\n"
"or try again with a smaller value of -m/--mmap_pages.\n"
"(current value: %d)\n", opts->mmap_pages);
+ else if (!is_power_of_2(opts->mmap_pages))
+ die("--mmap_pages/-m value must be a power of two.");
+
die("failed to mmap with %d (%s)\n", errno, strerror(errno));
}
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 963d63dde457..fa1837088ca8 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -563,6 +563,8 @@ int perf_evlist__mmap(struct perf_evlist *evlist, unsigned int pages,
/* 512 kiB: default amount of unprivileged mlocked memory */
if (pages == UINT_MAX)
pages = (512 * 1024) / page_size;
+ else if (!is_power_of_2(pages))
+ return -EINVAL;
mask = pages * page_size - 1;
diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index 0128906bac88..37be34dff798 100644
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -245,4 +245,15 @@ int readn(int fd, void *buf, size_t size);
#define _STR(x) #x
#define STR(x) _STR(x)
+/*
+ * Determine whether some value is a power of two, where zero is
+ * *not* considered a power of two.
+ */
+
+static inline __attribute__((const))
+bool is_power_of_2(unsigned long n)
+{
+ return (n != 0 && ((n & (n - 1)) == 0));
+}
+
#endif