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Only display prediction overlay when triggered by slowness

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Here we maintain the predictions always, but we only display the overlay
when either a threshold of smoothed round-trip time is met or temporarily
after a "glitch."
This commit is contained in:
Keith Winstein
2012-02-09 02:56:01 -05:00
parent 354dff39c8
commit 0b4cf8af3d
2 changed files with 68 additions and 19 deletions
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src/frontend/terminaloverlay.h
+26 -5
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@@ -45,11 +45,12 @@ namespace Overlay {
int col;
bool active; /* represents a prediction at all */
uint64_t tentative_until_epoch; /* when to show */
uint64_t prediction_time; /* used to find long-pending predictions */
ConditionalOverlay( uint64_t s_exp, int s_col, uint64_t s_tentative )
: expiration_frame( s_exp ), expiration_time( -1 ), col( s_col ),
: expiration_frame( s_exp ), expiration_time( uint64_t( -1 ) ), col( s_col ),
active( false ),
tentative_until_epoch( s_tentative )
tentative_until_epoch( s_tentative ), prediction_time( uint64_t( -1 ) )
{}
virtual ~ConditionalOverlay() {}
@@ -57,7 +58,10 @@ namespace Overlay {
bool tentative( uint64_t confirmed_epoch ) const { return tentative_until_epoch > confirmed_epoch; }
void reset( void ) { expiration_frame = expiration_time = tentative_until_epoch = -1; active = false; }
bool start_clock( uint64_t local_frame_acked, uint64_t now, unsigned int send_interval );
void expire( uint64_t s_exp ) { expiration_frame = s_exp; expiration_time = uint64_t(-1); }
void expire( uint64_t s_exp, uint64_t now )
{
expiration_frame = s_exp; expiration_time = uint64_t(-1); prediction_time = now;
}
};
class ConditionalCursorMove : public ConditionalOverlay {
@@ -137,6 +141,16 @@ namespace Overlay {
class PredictionEngine {
private:
static const uint64_t SRTT_TRIGGER_LOW = 20; /* <= ms cures SRTT trigger to show predictions */
static const uint64_t SRTT_TRIGGER_HIGH = 30; /* > ms starts SRTT trigger */
static const uint64_t FLAG_TRIGGER_LOW = 50; /* <= ms cures flagging */
static const uint64_t FLAG_TRIGGER_HIGH = 80; /* > ms starts flagging */
static const uint64_t GLITCH_THRESHOLD = 250; /* prediction outstanding this long is glitch */
static const uint64_t GLITCH_REPAIR_COUNT = 10; /* non-glitches required to cure glitch trigger */
static const uint64_t GLITCH_REPAIR_MININTERVAL = 150; /* required time in between non-glitches */
char last_byte;
Parser::UTF8Parser parser;
@@ -155,7 +169,10 @@ namespace Overlay {
void newline_carriage_return( const Framebuffer &fb );
bool flagging;
bool flagging; /* whether we are underlining predictions */
bool srtt_trigger; /* show predictions because of slow round trip time */
int glitch_trigger; /* show predictions temporarily because of long-pending prediction */
uint64_t last_quick_confirmation;
ConditionalCursorMove & cursor( void ) { assert( !cursors.empty() ); return cursors.back(); }
@@ -186,7 +203,11 @@ namespace Overlay {
local_frame_sent( 0 ), local_frame_acked( 0 ),
local_frame_late_acked( 0 ),
prediction_epoch( 1 ), confirmed_epoch( 0 ),
flagging( false ), last_scheduled_timeout( 0 ),
flagging( false ),
srtt_trigger( false ),
glitch_trigger( 0 ),
last_quick_confirmation( 0 ),
last_scheduled_timeout( 0 ),
send_interval( 250 )
{
}