Do you have an idea how much extra cpu this takes for high-bandwidth tracing?
I'm using xentrace for performance analysis, and it's already got a
measurable impact due to the disk bandwidth and copying. I'd like to
keep that as minimal as possible.
-George
On 11/30/06, Tony Breeds <tony@xxxxxxxxxxxxxxxxxx> wrote:
Use network byte order when writing data to disk, making the data portable to
any machine.
Signed-off-by: Tony Breeds <tony@xxxxxxxxxxxxxxxxxx>
---
tools/xentrace/xentrace.c | 47 ++++++++++++++++++++++++++++++++++-------
tools/xentrace/xentrace_format | 7 +++---
2 files changed, 44 insertions(+), 10 deletions(-)
Index: xen-unstable.hg-mainline.xentrace/tools/xentrace/xentrace.c
===================================================================
--- xen-unstable.hg-mainline.xentrace.orig/tools/xentrace/xentrace.c
+++ xen-unstable.hg-mainline.xentrace/tools/xentrace/xentrace.c
@@ -28,6 +28,20 @@
#include <xenctrl.h>
+#include <arpa/inet.h> /* hton*(), ntoh*() */
+#include <endian.h>
+
+/* There is no 64-bit htonll, so create one */
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+#define htonll(x) ( (((uint64_t)htonl(x)) << 32) + htonl(x >> 32) )
+#define ntohll(x) ( (((uint64_t)ntohl(x)) << 32) + ntohl(x >> 32) )
+#else
+#define htonll(x) (x)
+#define ntohll(x) (x)
+#endif
+
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
#define PERROR(_m, _a...) \
do { \
int __saved_errno = errno; \
@@ -90,12 +104,30 @@ struct timespec millis_to_timespec(unsig
* Outputs the trace record to a filestream, prepending the CPU ID of the
* source trace buffer.
*/
-void write_rec(unsigned int cpu, struct t_rec *rec, FILE *out)
+void write_rec(uint32_t cpu, struct t_rec *rec, FILE *out)
{
size_t written = 0;
- written += fwrite(&cpu, sizeof(cpu), 1, out);
- written += fwrite(rec, sizeof(*rec), 1, out);
- if ( written != 2 )
+ int i;
+ /* Place network byte order representation in temp vars, rather than
+ * write back into kernel/xen memory */
+ uint64_t tmp64;
+ uint32_t tmp32;
+
+ tmp32 = htonl(cpu);
+ written += fwrite(&tmp32, sizeof(tmp32), 1, out);
+
+ tmp64 = htonll(rec->cycles);
+ written += fwrite(&tmp64, sizeof(tmp64), 1, out);
+
+ tmp32 = htonl(rec->event);
+ written += fwrite(&tmp32, sizeof(tmp32), 1, out);
+
+ for ( i=0; i<ARRAY_SIZE(rec->data); i++ ) {
+ tmp64 = htonl(rec->data[i]);
+ written += fwrite(&tmp64, sizeof(tmp64), 1, out);
+ }
+
+ if ( written != 8 )
{
PERROR("Failed to write trace record");
exit(EXIT_FAILURE);
@@ -147,6 +179,7 @@ struct t_buf *map_tbufs(unsigned long tb
exit(EXIT_FAILURE);
}
+ /* On PPC (At least) the DOMID arg is ignored in dom0 */
tbufs_mapped = xc_map_foreign_range(xc_handle, DOMID_XEN,
size * num, PROT_READ | PROT_WRITE,
tbufs_mfn);
@@ -253,7 +286,7 @@ struct t_rec **init_rec_ptrs(struct t_bu
/**
* get_num_cpus - get the number of logical CPUs
*/
-unsigned int get_num_cpus(void)
+uint32_t get_num_cpus(void)
{
xc_physinfo_t physinfo;
int xc_handle = xc_interface_open();
@@ -282,14 +315,14 @@ unsigned int get_num_cpus(void)
*/
int monitor_tbufs(FILE *logfile)
{
- int i;
+ uint32_t i;
void *tbufs_mapped; /* pointer to where the tbufs are mapped */
struct t_buf **meta; /* pointers to the trace buffer metadata */
struct t_rec **data; /* pointers to the trace buffer data areas
* where they are mapped into user space. */
unsigned long tbufs_mfn; /* mfn of the tbufs */
- unsigned int num; /* number of trace buffers / logical CPUS */
+ uint32_t num; /* number of trace buffers / logical CPUS */
unsigned long size; /* size of a single trace buffer */
int size_in_recs;
Index: xen-unstable.hg-mainline.xentrace/tools/xentrace/xentrace_format
===================================================================
--- xen-unstable.hg-mainline.xentrace.orig/tools/xentrace/xentrace_format
+++ xen-unstable.hg-mainline.xentrace/tools/xentrace/xentrace_format
@@ -84,10 +84,11 @@ interrupted = 0
defs = read_defs(arg[0])
# structure of trace record + prepended CPU id (as output by xentrace):
-# CPU(I) TSC(Q) EVENT(L) D1(L) D2(L) D3(L) D4(L) D5(L)
+# CPU(L) TSC(Q) EVENT(L) D1(Q) D2(Q) D3(Q) D4(Q) D5(Q)
# read CPU id separately to avoid structure packing problems on 64-bit arch.
-CPUREC = "I"
-TRCREC = "QLLLLLL"
+# Force network byte order.
+CPUREC = "!L"
+TRCREC = "!QLQQQQQ"
last_tsc = [0]
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