[Spice-devel] [PATCH] Use non-zero data for initial ping

[David Jaša]

Yaniv Kaul píše v Po 13. 02. 2012 v 23:11 +0200:
> While the best thing would have been to pass the first image already to 
> the client using those 256K (and calculate the bandwidth based on the 
> first data passed to the client and continue to do so, as the protocol 
> continues),

upstream & downstream bugs requesting it:
http://bugs.freedesktop.org/show_bug.cgi?id=43756
https://bugzilla.redhat.com/show_bug.cgi?id=787197

David

>  the next best thing would probably be pass *some* image to 
> the client - some JPEG compressed logo or something.
> This is:
> (1) already quite compressed.
> (2) useful in some way.
> (3) probably 'cheaper' than creating some random data.
> 
> I think QEMU has this feature (off by default) to load a bootsplash 
> image as part of the BIOS. I wonder if it can be somehow re-used.
> 
> Y.
> 
> 
> On 02/13/2012 09:48 PM, Dan McGee wrote:
> > 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<dpmcgee at 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,
> 
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-- 

David Jaša, RHCE

SPICE QE based in Brno
GPG Key:     22C33E24 
Fingerprint: 513A 060B D1B4 2A72 7F0D 0278 B125 CD00 22C3 3E24