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transmission/libtransmission/cache.c

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/*
* This file Copyright (C) Mnemosyne LLC
*
* This file is licensed by the GPL version 2. Works owned by the
* Transmission project are granted a special exemption to clause 2(b)
* so that the bulk of its code can remain under the MIT license.
* This exemption does not extend to derived works not owned by
* the Transmission project.
*
* $Id$
*/
#include <stdlib.h> /* qsort() */
#include <event2/buffer.h>
#include "transmission.h"
#include "cache.h"
#include "inout.h"
#include "peer-common.h" /* MAX_BLOCK_SIZE */
#include "ptrarray.h"
#include "torrent.h"
#include "utils.h"
#define MY_NAME "Cache"
#define dbgmsg( ... ) \
do { \
if( tr_deepLoggingIsActive( ) ) \
tr_deepLog( __FILE__, __LINE__, MY_NAME, __VA_ARGS__ ); \
} while( 0 )
/****
*****
****/
struct cache_block
{
tr_torrent * tor;
tr_piece_index_t piece;
uint32_t offset;
uint32_t length;
time_t time;
tr_block_index_t block;
struct evbuffer * evbuf;
};
struct tr_cache
{
tr_ptrArray blocks;
int max_blocks;
size_t max_bytes;
size_t disk_writes;
size_t disk_write_bytes;
size_t cache_writes;
size_t cache_write_bytes;
};
/****
*****
****/
struct run_info
{
int pos;
int rank;
time_t last_block_time;
bool is_multi_piece;
bool is_piece_done;
unsigned len;
};
/* return a count of how many contiguous blocks there are starting at this pos */
static int
getBlockRun( const tr_cache * cache, int pos, struct run_info * info )
{
int i;
const int n = tr_ptrArraySize( &cache->blocks );
const struct cache_block ** blocks = (const struct cache_block**) tr_ptrArrayBase( &cache->blocks );
const struct cache_block * ref = blocks[pos];
tr_block_index_t block = ref->block;
for( i=pos; i<n; ++i, ++block ) {
const struct cache_block * b = blocks[i];
if( b->block != block ) break;
if( b->tor != ref->tor ) break;
//fprintf( stderr, "pos %d tor %d block %zu time %zu\n", i, b->tor->uniqueId, (size_t)b->block, (size_t)b->time );
}
//fprintf( stderr, "run is %d long from [%d to %d)\n", (int)(i-pos), i, (int)pos );
if( info != NULL ) {
const struct cache_block * b = blocks[i-1];
info->last_block_time = b->time;
info->is_piece_done = tr_cpPieceIsComplete( &b->tor->completion, b->piece );
info->is_multi_piece = b->piece != blocks[pos]->piece ? true : false;
info->len = i - pos;
info->pos = pos;
}
return i-pos;
}
/* higher rank comes before lower rank */
static int
compareRuns( const void * va, const void * vb )
{
const struct run_info * a = va;
const struct run_info * b = vb;
return b->rank - a->rank;
}
enum
{
MULTIFLAG = 0x1000,
DONEFLAG = 0x2000,
SESSIONFLAG = 0x4000
};
/* Calculte runs
* - Stale runs, runs sitting in cache for a long time or runs not growing, get priority.
* Returns number of runs.
*/
static int
calcRuns( tr_cache * cache, struct run_info * runs )
{
const int n = tr_ptrArraySize( &cache->blocks );
int i = 0, pos;
const time_t now = tr_time();
for( pos = 0; pos < n; pos += runs[i++].len )
{
int rank = getBlockRun( cache, pos, &runs[i] );
/* This adds ~2 to the relative length of a run for every minute it has
* languished in the cache. */
rank += ( now - runs[i].last_block_time ) / 32;
/* Flushing stale blocks should be a top priority as the probability of them
* growing is very small, for blocks on piece boundaries, and nonexistant for
* blocks inside pieces. */
rank |= runs[i].is_piece_done ? DONEFLAG : 0;
/* Move the multi piece runs higher */
rank |= runs[i].is_multi_piece ? MULTIFLAG : 0;
runs[i].rank = rank;
//fprintf(stderr,"block run at pos %d of length %d and age %ld adjusted +%d\n",runs[i].pos,runs[i].len,now-runs[i].last_block_time,rank-runs[i].len);
}
//fprintf( stderr, "%d block runs\n", i );
qsort( runs, i, sizeof( struct run_info ), compareRuns );
return i;
}
static int
flushContiguous( tr_cache * cache, int pos, int n )
{
int i;
int err = 0;
uint8_t * buf = tr_new( uint8_t, n * MAX_BLOCK_SIZE );
uint8_t * walk = buf;
struct cache_block ** blocks = (struct cache_block**) tr_ptrArrayBase( &cache->blocks );
struct cache_block * b = blocks[pos];
tr_torrent * tor = b->tor;
const tr_piece_index_t piece = b->piece;
const uint32_t offset = b->offset;
//fprintf( stderr, "flushing %d contiguous blocks [%d-%d) from cache to disk\n", n, pos, n+pos );
for( i=pos; i<pos+n; ++i ) {
b = blocks[i];
evbuffer_copyout( b->evbuf, walk, b->length );
walk += b->length;
evbuffer_free( b->evbuf );
tr_free( b );
}
tr_ptrArrayErase( &cache->blocks, pos, pos+n );
#if 0
tr_tordbg( tor, "Writing to disk piece %d, offset %d, len %d", (int)piece, (int)offset, (int)(walk-buf) );
tr_ndbg( MY_NAME, "Removing %d blocks from cache, rank: %d - %d left", n, rank, tr_ptrArraySize(&cache->blocks) );
fprintf( stderr, "%s - Writing to disk piece %d, offset %d, len %d\n", tr_torrentName(tor), (int)piece, (int)offset, (int)(walk-buf) );
fprintf( stderr, "%s - Removing %d blocks from cache; %d left\n", MY_NAME, n, tr_ptrArraySize(&cache->blocks) );
#endif
err = tr_ioWrite( tor, piece, offset, walk-buf, buf );
tr_free( buf );
++cache->disk_writes;
cache->disk_write_bytes += walk-buf;
return err;
}
static int
flushRuns( tr_cache * cache, struct run_info * runs, int n )
{
int i, j, err = 0;
for( i = 0; !err && i < n; ++i )
{
err = flushContiguous( cache, runs[i].pos, runs[i].len );
for( j = i + 1; j < n; ++j )
if( runs[j].pos > runs[i].pos )
runs[j].pos -= runs[i].len;
}
return err;
}
static int
cacheTrim( tr_cache * cache )
{
int err = 0;
if( tr_ptrArraySize( &cache->blocks ) > cache->max_blocks )
{
/* Amount of cache that should be removed by the flush. This influences how large
* runs can grow as well as how often flushes will happen. */
const int cacheCutoff = 1 + cache->max_blocks / 4;
struct run_info * runs = tr_new( struct run_info, tr_ptrArraySize( &cache->blocks ) );
int i = 0, j = 0;
calcRuns( cache, runs );
while( j < cacheCutoff )
j += runs[i++].len;
err = flushRuns( cache, runs, i );
tr_free( runs );
}
return err;
}
/***
****
***/
static int
getMaxBlocks( int64_t max_bytes )
{
return max_bytes / (double)MAX_BLOCK_SIZE;
}
int
tr_cacheSetLimit( tr_cache * cache, int64_t max_bytes )
{
char buf[128];
cache->max_bytes = max_bytes;
cache->max_blocks = getMaxBlocks( max_bytes );
tr_formatter_mem_B( buf, cache->max_bytes, sizeof( buf ) );
tr_ndbg( MY_NAME, "Maximum cache size set to %s (%d blocks)", buf, cache->max_blocks );
return cacheTrim( cache );
}
int64_t
tr_cacheGetLimit( const tr_cache * cache )
{
return cache->max_bytes;
}
tr_cache *
tr_cacheNew( int64_t max_bytes )
{
tr_cache * cache = tr_new0( tr_cache, 1 );
cache->blocks = TR_PTR_ARRAY_INIT;
cache->max_bytes = max_bytes;
cache->max_blocks = getMaxBlocks( max_bytes );
return cache;
}
void
tr_cacheFree( tr_cache * cache )
{
assert( tr_ptrArrayEmpty( &cache->blocks ) );
tr_ptrArrayDestruct( &cache->blocks, NULL );
tr_free( cache );
}
/***
****
***/
static int
cache_block_compare( const void * va, const void * vb )
{
const struct cache_block * a = va;
const struct cache_block * b = vb;
/* primary key: torrent id */
if( a->tor->uniqueId != b->tor->uniqueId )
return a->tor->uniqueId < b->tor->uniqueId ? -1 : 1;
/* secondary key: block # */
if( a->block != b->block )
return a->block < b->block ? -1 : 1;
/* they're equal */
return 0;
}
static struct cache_block *
findBlock( tr_cache * cache,
tr_torrent * torrent,
tr_piece_index_t piece,
uint32_t offset )
{
struct cache_block key;
key.tor = torrent;
key.block = _tr_block( torrent, piece, offset );
return tr_ptrArrayFindSorted( &cache->blocks, &key, cache_block_compare );
}
int
tr_cacheWriteBlock( tr_cache * cache,
tr_torrent * torrent,
tr_piece_index_t piece,
uint32_t offset,
uint32_t length,
struct evbuffer * writeme )
{
struct cache_block * cb = findBlock( cache, torrent, piece, offset );
if( cb == NULL )
{
cb = tr_new( struct cache_block, 1 );
cb->tor = torrent;
cb->piece = piece;
cb->offset = offset;
cb->length = length;
cb->block = _tr_block( torrent, piece, offset );
cb->evbuf = evbuffer_new( );
tr_ptrArrayInsertSorted( &cache->blocks, cb, cache_block_compare );
}
cb->time = tr_time();
assert( cb->length == length );
evbuffer_drain( cb->evbuf, evbuffer_get_length( cb->evbuf ) );
evbuffer_remove_buffer( writeme, cb->evbuf, cb->length );
++cache->cache_writes;
cache->cache_write_bytes += cb->length;
return cacheTrim( cache );
}
int
tr_cacheReadBlock( tr_cache * cache,
tr_torrent * torrent,
tr_piece_index_t piece,
uint32_t offset,
uint32_t len,
uint8_t * setme )
{
int err = 0;
struct cache_block * cb = findBlock( cache, torrent, piece, offset );
if( cb )
evbuffer_copyout( cb->evbuf, setme, len );
else
err = tr_ioRead( torrent, piece, offset, len, setme );
return err;
}
int
tr_cachePrefetchBlock( tr_cache * cache,
tr_torrent * torrent,
tr_piece_index_t piece,
uint32_t offset,
uint32_t len )
{
int err = 0;
struct cache_block * cb = findBlock( cache, torrent, piece, offset );
if( cb == NULL )
err = tr_ioPrefetch( torrent, piece, offset, len );
return err;
}
/***
****
***/
static int
findBlockPos( tr_cache * cache, tr_torrent * torrent, tr_piece_index_t block )
{
struct cache_block key;
key.tor = torrent;
key.block = block;
return tr_ptrArrayLowerBound( &cache->blocks, &key, cache_block_compare, NULL );
}
int tr_cacheFlushDone( tr_cache * cache )
{
int err = 0;
if( tr_ptrArraySize( &cache->blocks ) > 0 )
{
struct run_info * runs = tr_new( struct run_info, tr_ptrArraySize( &cache->blocks ) );
int i = 0, n;
n = calcRuns( cache, runs );
while( i < n && ( runs[i].is_piece_done || runs[i].is_multi_piece ) )
runs[i++].rank |= SESSIONFLAG;
err = flushRuns( cache, runs, i );
tr_free( runs );
}
return err;
}
int
tr_cacheFlushFile( tr_cache * cache, tr_torrent * torrent, tr_file_index_t i )
{
int pos;
int err = 0;
tr_block_index_t first;
tr_block_index_t last;
tr_torGetFileBlockRange( torrent, i, &first, &last );
pos = findBlockPos( cache, torrent, first );
dbgmsg( "flushing file %d from cache to disk: blocks [%zu...%zu]", (int)i, (size_t)first, (size_t)last );
/* flush out all the blocks in that file */
while( !err && ( pos < tr_ptrArraySize( &cache->blocks ) ) )
{
const struct cache_block * b = tr_ptrArrayNth( &cache->blocks, pos );
if( b->tor != torrent ) break;
if( ( b->block < first ) || ( b->block > last ) ) break;
err = flushContiguous( cache, pos, getBlockRun( cache, pos, NULL ) );
}
return err;
}
int
tr_cacheFlushTorrent( tr_cache * cache, tr_torrent * torrent )
{
int err = 0;
const int pos = findBlockPos( cache, torrent, 0 );
/* flush out all the blocks in that torrent */
while( !err && ( pos < tr_ptrArraySize( &cache->blocks ) ) )
{
const struct cache_block * b = tr_ptrArrayNth( &cache->blocks, pos );
if( b->tor != torrent ) break;
err = flushContiguous( cache, pos, getBlockRun( cache, pos, NULL ) );
}
return err;
}
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