[patch v7 09/24] btrace: increase buffer size

Markus Metzger
2013-11-29T14:39:38Z

Try to allocate as much buffer as we can for each thread with a maximum
of 64KB.

2013-11-29 Markus Metzger <markus.t.metzger@intel.com>

* common/linux-btrace.c (linux_enable_btrace): Enlarge buffer.

---
gdb/common/linux-btrace.c | 25 +++++++++++++++----------
1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/gdb/common/linux-btrace.c b/gdb/common/linux-btrace.c
index aa2b0ae..801505b 100644
--- a/gdb/common/linux-btrace.c
+++ b/gdb/common/linux-btrace.c
@@ -423,7 +423,7 @@ struct btrace_target_info *
linux_enable_btrace (ptid_t ptid)
{
struct btrace_target_info *tinfo;
- int pid;
+ int pid, pg;

tinfo = xzalloc (sizeof (*tinfo));
tinfo->ptid = ptid;
@@ -451,17 +451,22 @@ linux_enable_btrace (ptid_t ptid)
if (tinfo->file < 0)
goto err;

- /* We hard-code the trace buffer size.
- At some later time, we should make this configurable. */
- tinfo->size = 1;
- tinfo->buffer = mmap (NULL, perf_event_mmap_size (tinfo),
- PROT_READ, MAP_SHARED, tinfo->file, 0);
- if (tinfo->buffer == MAP_FAILED)
- goto err_file;
+ /* We try to allocate as much buffer as we can get.
+ We could allow the user to specify the size of the buffer, but then
+ we'd leave this search for the maximum buffer size to him. */
+ for (pg = 4; pg >= 0; --pg)
+ {
+ /* The number of pages we request needs to be a power of two. */
+ tinfo->size = 1 << pg;
+ tinfo->buffer = mmap (NULL, perf_event_mmap_size (tinfo),
+ PROT_READ, MAP_SHARED, tinfo->file, 0);
+ if (tinfo->buffer == MAP_FAILED)
+ continue;

- return tinfo;
+ return tinfo;
+ }

- err_file:
+ /* We were not able to allocate any buffer. */
close (tinfo->file);

err:
--
1.8.3.1