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authorØyvind Harboe <oyvind.harboe@zylin.com>2009-12-10 19:14:45 +0100
committerØyvind Harboe <oyvind.harboe@zylin.com>2009-12-11 09:17:23 +0100
commit97996214f593d0d1969446484598c58077da3965 (patch)
tree4e2840f75c848e0923a1039510bfdfcaf3b7e8bb /src
parent1c42606aea99e870f0ffd435390e29a160d019ee (diff)
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gdb_server: use more local variables in inner loop of fetching packetstiny refactoring to allow optimisation of inner loops
Some profiling information for arm7 16MHz GDB load operation shows gdb_get_packet_inner() near the very top. Each sample counts as 0.01 seconds. % cumulative self self total time seconds seconds calls Ts/call Ts/call name 52.91 2.27 2.27 embeddedice_write_dcc 11.89 2.78 0.51 gdb_get_packet_inner 8.86 3.16 0.38 memcpy 3.26 3.30 0.14 idle_thread_main(unsigned int) 3.03 3.43 0.13 cyg_in_cksum Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>
Diffstat (limited to 'src')
-rw-r--r--src/server/gdb_server.c104
1 files changed, 73 insertions, 31 deletions
diff --git a/src/server/gdb_server.c b/src/server/gdb_server.c
index ea92d3ba..8798ae03 100644
--- a/src/server/gdb_server.c
+++ b/src/server/gdb_server.c
@@ -149,30 +149,11 @@ int check_pending(struct connection *connection, int timeout_s, int *got_data)
return ERROR_OK;
}
-int gdb_get_char(struct connection *connection, int* next_char)
+static int gdb_get_char_inner(struct connection *connection, int* next_char)
{
struct gdb_connection *gdb_con = connection->priv;
int retval = ERROR_OK;
-#ifdef _DEBUG_GDB_IO_
- char *debug_buffer;
-#endif
-
- if (gdb_con->buf_cnt-- > 0)
- {
- *next_char = *(gdb_con->buf_p++);
- if (gdb_con->buf_cnt > 0)
- connection->input_pending = 1;
- else
- connection->input_pending = 0;
-
-#ifdef _DEBUG_GDB_IO_
- LOG_DEBUG("returned char '%c' (0x%2.2x)", *next_char, *next_char);
-#endif
-
- return ERROR_OK;
- }
-
for (;;)
{
if (connection->service->type == CONNECTION_PIPE)
@@ -257,6 +238,50 @@ int gdb_get_char(struct connection *connection, int* next_char)
return retval;
}
+/**
+ * The cool thing about this fn is that it allows buf_p and buf_cnt to be
+ * held in registers in the inner loop.
+ *
+ * For small caches and embedded systems this is important!
+ */
+static inline int gdb_get_char_fast(struct connection *connection, int* next_char, char **buf_p, int *buf_cnt)
+{
+ int retval = ERROR_OK;
+
+ if ((*buf_cnt)-- > 0)
+ {
+ *next_char = **buf_p;
+ (*buf_p)++;
+ if (*buf_cnt > 0)
+ connection->input_pending = 1;
+ else
+ connection->input_pending = 0;
+
+#ifdef _DEBUG_GDB_IO_
+ LOG_DEBUG("returned char '%c' (0x%2.2x)", *next_char, *next_char);
+#endif
+
+ return ERROR_OK;
+ }
+
+ struct gdb_connection *gdb_con = connection->priv;
+ gdb_con->buf_p = *buf_p;
+ gdb_con->buf_cnt = *buf_cnt;
+ retval = gdb_get_char_inner(connection, next_char);
+ *buf_p = gdb_con->buf_p;
+ *buf_cnt = gdb_con->buf_cnt;
+
+ return retval;
+}
+
+
+int gdb_get_char(struct connection *connection, int* next_char)
+{
+ struct gdb_connection *gdb_con = connection->priv;
+ return gdb_get_char_fast(connection, next_char, &gdb_con->buf_p, &gdb_con->buf_cnt);
+}
+
+
int gdb_putback_char(struct connection *connection, int last_char)
{
struct gdb_connection *gdb_con = connection->priv;
@@ -461,27 +486,33 @@ static __inline__ int fetch_packet(struct connection *connection, int *checksum_
unsigned char my_checksum = 0;
char checksum[3];
int character;
- int retval;
+ int retval = ERROR_OK;
struct gdb_connection *gdb_con = connection->priv;
my_checksum = 0;
int count = 0;
count = 0;
+
+ /* move this over into local variables to use registers and give the
+ * more freedom to optimize */
+ char *buf_p = gdb_con->buf_p;
+ int buf_cnt = gdb_con->buf_cnt;
+
for (;;)
{
/* The common case is that we have an entire packet with no escape chars.
* We need to leave at least 2 bytes in the buffer to have
* gdb_get_char() update various bits and bobs correctly.
*/
- if ((gdb_con->buf_cnt > 2) && ((gdb_con->buf_cnt + count) < *len))
+ if ((buf_cnt > 2) && ((buf_cnt + count) < *len))
{
/* The compiler will struggle a bit with constant propagation and
* aliasing, so we help it by showing that these values do not
* change inside the loop
*/
int i;
- char *buf = gdb_con->buf_p;
- int run = gdb_con->buf_cnt - 2;
+ char *buf = buf_p;
+ int run = buf_cnt - 2;
i = 0;
int done = 0;
while (i < run)
@@ -513,19 +544,21 @@ static __inline__ int fetch_packet(struct connection *connection, int *checksum_
buffer[count++] = character & 0xff;
}
}
- gdb_con->buf_p += i;
- gdb_con->buf_cnt -= i;
+ buf_p += i;
+ buf_cnt -= i;
if (done)
break;
}
if (count > *len)
{
LOG_ERROR("packet buffer too small");
- return ERROR_GDB_BUFFER_TOO_SMALL;
+ retval = ERROR_GDB_BUFFER_TOO_SMALL;
+ break;
}
- if ((retval = gdb_get_char(connection, &character)) != ERROR_OK)
- return retval;
+ retval = gdb_get_char_fast(connection, &character, &buf_p, &buf_cnt);
+ if (retval != ERROR_OK)
+ break;
if (character == '#')
break;
@@ -535,8 +568,11 @@ static __inline__ int fetch_packet(struct connection *connection, int *checksum_
/* data transmitted in binary mode (X packet)
* uses 0x7d as escape character */
my_checksum += character & 0xff;
- if ((retval = gdb_get_char(connection, &character)) != ERROR_OK)
- return retval;
+
+ retval = gdb_get_char_fast(connection, &character, &buf_p, &buf_cnt);
+ if (retval != ERROR_OK)
+ break;
+
my_checksum += character & 0xff;
buffer[count++] = (character ^ 0x20) & 0xff;
}
@@ -547,6 +583,12 @@ static __inline__ int fetch_packet(struct connection *connection, int *checksum_
}
}
+ gdb_con->buf_p = buf_p;
+ gdb_con->buf_cnt = buf_cnt;
+
+ if (retval != ERROR_OK)
+ return retval;
+
*len = count;
if ((retval = gdb_get_char(connection, &character)) != ERROR_OK)