This prevents compression over things such as VPN links misleading us on
available bandwidth. The page used before was 4K worth of zeroes, which
isn't a very realistic test at all.
We now use a generated sequence of bytes that vary in value and offset
between consecutive values, causing compression programs to have a much
harder time reducing our ping packets to nothing.
Here are some comparisons of before/after using a small standalone
program that generates bytes in the same fashion:
Before:
4096 zerodata
43 zerodata.bz2
38 zerodata.gz
92 zerodata.xz
After:
4096 seqdata
1213 seqdata.bz2
4119 seqdata.gz
3208 seqdata.xz
Signed-off-by: Dan McGee <dpmc...@gmail.com>
---
This was a TODO item on the following page:
http://spice-space.org/page/Features/Bandwidth_monitoring
The standalone test program is below if anyone wants to try it out; simply pass
'4096' or similar as the first argument and you will get 4096 "random" bytes on
stdout that you can play with.
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char *argv[])
{
int i, total;
total = atoi(argv[1]);
for(i = 0; i < total; i++) {
div_t result = div(i, 256);
if(result.quot % 2 == 0) {
fputc((result.quot + 1) * result.rem, stdout);
} else {
fputc(512 - (result.quot * result.rem), stdout);
}
}
return 0;
}
server/main_channel.c | 24 ++++++++++++++++--------
1 files changed, 16 insertions(+), 8 deletions(-)
diff --git a/server/main_channel.c b/server/main_channel.c
index f7e1ab0..2ce20c0 100644
--- a/server/main_channel.c
+++ b/server/main_channel.c
@@ -22,6 +22,7 @@
#include <inttypes.h>
#include <stdint.h>
#include <stdio.h>
+#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
@@ -45,8 +46,6 @@
#include "red_channel.h"
#include "generated_marshallers.h"
-#define ZERO_BUF_SIZE 4096
-
#define REDS_MAX_SEND_IOVEC 100
#define NET_TEST_WARMUP_BYTES 0
@@ -54,8 +53,6 @@
#define PING_INTERVAL (1000 * 10)
-static uint8_t zero_page[ZERO_BUF_SIZE] = {0};
-
typedef struct RedsOutItem RedsOutItem;
struct RedsOutItem {
PipeItem base;
@@ -335,17 +332,28 @@ static void main_channel_marshall_ping(SpiceMarshaller
*m, int size, int ping_id
{
struct timespec time_space;
SpiceMsgPing ping;
+ uint8_t *ping_data;
+ int i;
ping.id = ping_id;
clock_gettime(CLOCK_MONOTONIC, &time_space);
ping.timestamp = time_space.tv_sec * 1000000LL + time_space.tv_nsec /
1000LL;
spice_marshall_msg_ping(m, &ping);
- while (size > 0) {
- int now = MIN(ZERO_BUF_SIZE, size);
- size -= now;
- spice_marshaller_add_ref(m, zero_page, now);
+ ping_data = spice_malloc(size);
+ /* this produces ascending and descending byte runs which vary in offset
+ * every 512 bytes, preventing prevents compression from being able to
+ * influence the resulting size of the ping data too much */
+ for(i = 0; i < size; i++) {
+ div_t result = div(i, 256);
+ if(result.quot % 2 == 0) {
+ ping_data[i] = (result.quot + 1) * result.rem;
+ } else {
+ ping_data[i] = 512 - (result.quot * result.rem);
+ }
}
+
+ spice_marshaller_add(m, ping_data, size);
}
void main_channel_push_mouse_mode(MainChannel *main_chan, int current_mode,
--
1.7.9
_______________________________________________
Spice-devel mailing list
Spice-devel@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/spice-devel
