Commit 5df2e973 authored by Pierre d'Herbemont's avatar Pierre d'Herbemont

stream: Add a new method for buffering access: A*Immediate method.

It is much more efficient regarding latency as it doesn't bufferize more than needed, and let the module access take care of that eventually.

Enable with --use-stream-immediate. We may want to default it.

Note: --use-stream-immediate will be only effective on access that don't provide pf_block() for now. This is because I didn't benchmark against the Block method.

Here the gain that I did measure is about 200ms (less latency) when using the http access on a loopback.
parent 446bfcd5
......@@ -27,15 +27,18 @@
#include <vlc_common.h>
#include <assert.h>
#include "input_internal.h"
#undef STREAM_DEBUG
/* TODO:
* - tune the 2 methods
* - tune the 2 methods (block/stream)
* - compute cost for seek
* - improve stream mode seeking with closest segments
* - ...
* - Maybe remove (block/stream) in favour of immediate
*/
/* Two methods:
......@@ -43,6 +46,9 @@
* One linked list of data read
* - using pf_read
* More complex scheme using mutliple track to avoid seeking
* - using directly the access (only indirection for peeking).
* This method is known to introduce much less latency.
* It should probably defaulted (instead of the stream method (2)).
*/
/* How many tracks we have, currently only used for stream mode */
......@@ -101,11 +107,18 @@ typedef struct
} access_entry_t;
typedef enum stream_read_method_t
{
Immediate,
Block,
Stream
} stream_read_method_t;
struct stream_sys_t
{
access_t *p_access;
bool b_block; /* Block method (1) or stream */
stream_read_method_t method; /* method to use */
int64_t i_pos; /* Current reading offset */
......@@ -138,6 +151,13 @@ struct stream_sys_t
} stream;
/* Method 3: for pf_read */
struct
{
int64_t i_end;
uint8_t *p_buffer;
} immediate;
/* Peek temporary buffer */
int i_peek;
uint8_t *p_peek;
......@@ -182,12 +202,47 @@ static int AStreamSeekStream( stream_t *s, int64_t i_pos );
static void AStreamPrebufferStream( stream_t *s );
static int AReadStream( stream_t *s, void *p_read, int i_read );
/* Method 3 */
static int AStreamReadImmediate( stream_t *s, void *p_read, int i_read );
static int AStreamPeekImmediate( stream_t *s, const uint8_t **pp_peek, int i_read );
static int AStreamSeekImmediate( stream_t *s, int64_t i_pos );
/* Common */
static int AStreamControl( stream_t *s, int i_query, va_list );
static void AStreamDestroy( stream_t *s );
static void UStreamDestroy( stream_t *s );
static int ASeek( stream_t *s, int64_t i_pos );
/****************************************************************************
* Method 3 helpers:
****************************************************************************/
static inline int64_t stream_buffered_size( stream_t *s )
{
return s->p_sys->immediate.i_end;
}
static inline void stream_buffer_empty( stream_t *s, int length )
{
length = __MAX( stream_buffered_size( s ), length );
if( length )
{
memmove( s->p_sys->immediate.p_buffer,
s->p_sys->immediate.p_buffer + length,
stream_buffered_size( s ) - length );
}
s->p_sys->immediate.i_end -= length;
}
static inline void stream_buffer_fill( stream_t *s, int length )
{
s->p_sys->immediate.i_end += length;
}
static inline uint8_t * stream_buffer( stream_t *s )
{
return s->p_sys->immediate.p_buffer;
}
/****************************************************************************
* stream_UrlNew: create a stream from a access
......@@ -254,7 +309,13 @@ stream_t *stream_AccessNew( access_t *p_access, bool b_quick )
/* Common field */
p_sys->p_access = p_access;
p_sys->b_block = p_access->pf_block ? true : false;
if( p_access->pf_block )
p_sys->method = Block;
else if (var_CreateGetBool( s, "use-stream-immediate"))
p_sys->method = Immediate;
else
p_sys->method = Stream;
p_sys->i_pos = p_access->info.i_pos;
/* Stats */
......@@ -340,8 +401,9 @@ stream_t *stream_AccessNew( access_t *p_access, bool b_quick )
p_sys->i_peek = 0;
p_sys->p_peek = NULL;
if( p_sys->b_block )
if( p_sys->method == Block )
{
msg_Dbg( s, "Using AStream*Block" );
s->pf_read = AStreamReadBlock;
s->pf_peek = AStreamPeekBlock;
......@@ -362,10 +424,33 @@ stream_t *stream_AccessNew( access_t *p_access, bool b_quick )
goto error;
}
}
else
else if (p_sys->method == Immediate)
{
msg_Dbg( s, "Using AStream*Immediate" );
s->pf_read = AStreamReadImmediate;
s->pf_peek = AStreamPeekImmediate;
/* Allocate/Setup our tracks (useful to peek)*/
p_sys->immediate.i_end = 0;
p_sys->immediate.p_buffer = malloc( STREAM_CACHE_SIZE );
msg_Dbg( s, "p_buffer %p-%p", p_sys->immediate.p_buffer,
p_sys->immediate.p_buffer + STREAM_CACHE_SIZE );
if( p_sys->immediate.p_buffer == NULL )
{
msg_Err( s, "Out of memory when allocating stream cache (%d bytes)",
STREAM_CACHE_SIZE );
goto error;
}
}
else /* ( p_sys->method == Stream ) */
{
int i;
msg_Dbg( s, "Using AStream*Stream" );
s->pf_read = AStreamReadStream;
s->pf_peek = AStreamPeekStream;
......@@ -409,7 +494,7 @@ stream_t *stream_AccessNew( access_t *p_access, bool b_quick )
return s;
error:
if( p_sys->b_block )
if( p_sys->method == Block )
{
/* Nothing yet */
}
......@@ -436,7 +521,7 @@ static void AStreamDestroy( stream_t *s )
vlc_object_detach( s );
if( p_sys->b_block ) block_ChainRelease( p_sys->block.p_first );
if( p_sys->method == Block ) block_ChainRelease( p_sys->block.p_first );
else free( p_sys->stream.p_buffer );
free( p_sys->p_peek );
......@@ -473,7 +558,7 @@ void stream_AccessReset( stream_t *s )
p_sys->i_pos = p_sys->p_access->info.i_pos;
if( p_sys->b_block )
if( p_sys->method == Block )
{
block_ChainRelease( p_sys->block.p_first );
......@@ -488,7 +573,11 @@ void stream_AccessReset( stream_t *s )
/* Do the prebuffering */
AStreamPrebufferBlock( s );
}
else
else if( p_sys->method == Immediate )
{
stream_buffer_empty( s, stream_buffered_size( s ) );
}
else /* ( p_sys->method == Stream ) */
{
int i;
......@@ -572,9 +661,11 @@ static int AStreamControl( stream_t *s, int i_query, va_list args )
case STREAM_SET_POSITION:
i_64 = (int64_t)va_arg( args, int64_t );
if( p_sys->b_block )
if( p_sys->method == Block )
return AStreamSeekBlock( s, i_64 );
else
else if( p_sys->method == Immediate )
return AStreamSeekImmediate( s, i_64 );
else /* ( p_sys->method == Stream ) */
return AStreamSeekStream( s, i_64 );
case STREAM_GET_MTU:
......@@ -1420,6 +1511,119 @@ static void AStreamPrebufferStream( stream_t *s )
}
}
/****************************************************************************
* Method 3:
****************************************************************************/
static int AStreamReadImmediate( stream_t *s, void *p_read, int i_read )
{
stream_sys_t *p_sys = s->p_sys;
#ifdef STREAM_DEBUG
msg_Dbg( s, "AStreamReadImmediate p_read=%p i_read=%d",
p_read, i_read );
#endif
if( p_read == NULL )
{
/* seek within this stream if possible, else use plain old read and discard */
stream_sys_t *p_sys = s->p_sys;
access_t *p_access = p_sys->p_access;
bool b_aseek;
access_Control( p_access, ACCESS_CAN_SEEK, &b_aseek );
if( b_aseek )
return AStreamSeekStream( s, p_sys->i_pos + i_read ) ? 0 : i_read;
}
/* First, check if we already have some data in the buffer,
* that we could copy directly */
int i_copy = __MIN( stream_buffered_size( s ), i_read );
if( i_copy )
{
#ifdef STREAM_DEBUG
msg_Dbg( s, "AStreamReadImmediate: copy %d from %p", i_copy, stream_buffer( s ) );
#endif
assert( i_copy <= STREAM_CACHE_SIZE );
if( p_read )
{
memcpy( p_read, stream_buffer( s ), i_copy );
p_read = (uint8_t *)p_read + i_copy;
}
}
/* Now that we've read our buffer we don't need its i_copy bytes */
stream_buffer_empty( s, i_copy );
/* Now check if we have still to really read some data */
int i_to_read = i_read - i_copy;
if( i_to_read )
{
i_to_read = AReadStream( s, p_read, i_to_read );
}
p_sys->i_pos += i_to_read;
return i_to_read + i_copy;
}
static int AStreamPeekImmediate( stream_t *s, const uint8_t **pp_peek, int i_read )
{
#ifdef STREAM_DEBUG
msg_Dbg( s, "AStreamPeekImmediate: %d size=%"PRId64,
i_read, size_buffered_size( s ) );
#endif
/* Avoid problem, but that shouldn't happen */
if( i_read > STREAM_CACHE_SIZE / 2 )
i_read = STREAM_CACHE_SIZE / 2;
int i_to_read = i_read - stream_buffered_size( s );
if( i_to_read > 0 )
{
#ifdef STREAM_DEBUG
msg_Dbg( s, "AStreamPeekImmediate: Reading %d",
i_to_read );
#endif
i_to_read = AReadStream( s, stream_buffer( s ) + stream_buffered_size( s ),
i_to_read );
if( i_to_read > 0 )
stream_buffer_fill( s, i_to_read );
}
*pp_peek = stream_buffer( s );
return __MIN(stream_buffered_size( s ), i_read);
}
static int AStreamSeekImmediate( stream_t *s, int64_t i_pos )
{
stream_sys_t *p_sys = s->p_sys;
access_t *p_access = p_sys->p_access;
bool b_aseek;
#ifdef STREAM_DEBUG
msg_Dbg( s, "AStreamSeekImmediate to %"PRId64" pos=%"PRId64
i_pos, p_sys->i_pos );
#endif
access_Control( p_access, ACCESS_CAN_SEEK, &b_aseek );
if( !b_aseek )
{
/* We can't do nothing */
msg_Dbg( s, "AStreamSeekImmediate: can't seek" );
return VLC_EGENERIC;
}
/* Just reset our buffer */
stream_buffer_empty( s, stream_buffered_size( s ) );
if( ASeek( s, i_pos ) ) return VLC_EGENERIC;
return VLC_SUCCESS;
}
/****************************************************************************
* stream_ReadLine:
......
......@@ -993,6 +993,12 @@ static const char *const ppsz_clock_descriptions[] =
#define MINIMIZE_THREADS_LONGTEXT N_( \
"This option minimizes the number of threads needed to run VLC.")
#define USE_STREAM_IMMEDIATE N_("(Experimental) Use the StreamImmediate " \
"method and minimize the caching done at the access level.")
#define USE_STREAM_IMMEDIATE_LONGTEXT N_( \
"This option is useful if you want to lower the latency when " \
"reading a stream")
#define PLUGIN_PATH_TEXT N_("Modules search path")
#define PLUGIN_PATH_LONGTEXT N_( \
"Additional path for VLC to look for its modules. You can add " \
......@@ -1814,6 +1820,9 @@ vlc_module_begin();
MINIMIZE_THREADS_LONGTEXT, true );
change_need_restart();
add_bool( "use-stream-immediate", false, NULL,
USE_STREAM_IMMEDIATE, USE_STREAM_IMMEDIATE_LONGTEXT, false );
#if !defined(__APPLE__) && !defined(SYS_BEOS) && defined(LIBVLC_USE_PTHREAD)
add_bool( "rt-priority", false, NULL, RT_PRIORITY_TEXT,
RT_PRIORITY_LONGTEXT, true );
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment