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transmission/libtransmission/cache.c

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/*
* This file Copyright (C) 2010 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 "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"
/****
*****
****/
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;
uint8_t * buf;
};
struct tr_cache
{
tr_ptrArray blocks;
int maxBlocks;
size_t maxMiB;
size_t disk_writes;
size_t disk_write_bytes;
size_t cache_writes;
size_t cache_write_bytes;
};
/****
*****
****/
struct run_info
{
time_t last_block_time;
tr_bool is_aligned;
};
/* 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 ) {
info->last_block_time = blocks[i-1]->time;
info->is_aligned = (blocks[pos]->block % 2 == 0) ? TRUE : FALSE;
}
return i-pos;
}
/* return the starting index of the longest contiguous run of blocks BUT:
* 1 - Length of run must be even.
* 2 - Run must begin with a even block.
* 3 - Oldest run is preferred.
*/
static int
findChunk2Discard( tr_cache * cache, int * setme_n )
{
const int n = tr_ptrArraySize( &cache->blocks );
int pos;
int bestpos = 0;
unsigned bestlen = 1;
unsigned jump;
time_t oldest_time = ~0;
struct run_info run;
for( pos=0; pos<n; pos+=jump )
{
unsigned len = getBlockRun( cache, pos, &run );
jump = len;
/* shortcut */
if( len < bestlen )
continue;
/* check alignment */
if( len % 2 == 0 ) {
if( !run.is_aligned )
/* Let it grow. Otherwise we contribute to fragmentation */
continue;
} else {
if( len != 1 ) {
--len;
if( !run.is_aligned ) {
++pos;
--jump;
}
}
}
if( bestlen < len ) {
bestlen = len;
bestpos = pos;
oldest_time = run.last_block_time;
} else if( (bestlen == len) && (oldest_time > run.last_block_time) ) {
bestpos = pos;
oldest_time = run.last_block_time;
}
}
//fprintf( stderr, "DISCARDED run is %d long from [%d to %d)\n", bestlen, bestpos, bestpos+bestlen );
*setme_n = bestlen;
return bestpos;
}
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 from [%d to %d)\n", n, pos, n+pos );
for( i=pos; i<pos+n; ++i ) {
b = blocks[i];
memcpy( walk, b->buf, b->length );
walk += b->length;
tr_free( b->buf );
tr_free( b );
}
tr_ptrArrayErase( &cache->blocks, pos, pos+n );
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; %d left", n, 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) );
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
cacheTrim( tr_cache * cache )
{
int err = 0;
while( !err && ( tr_ptrArraySize( &cache->blocks ) > cache->maxBlocks ) )
{
int n;
const int i = findChunk2Discard( cache, &n );
err = flushContiguous( cache, i, n );
}
return err;
}
/***
****
***/
static int
getMaxBlocks( double maxMiB )
{
const double maxBytes = maxMiB * (1024 * 1024);
return maxBytes / MAX_BLOCK_SIZE;
}
int
tr_cacheSetLimit( tr_cache * cache, double maxMiB )
{
cache->maxMiB = maxMiB;
cache->maxBlocks = getMaxBlocks( maxMiB );
tr_ndbg( MY_NAME, "Maximum cache size set to %.2f MiB (%d blocks)", maxMiB, cache->maxBlocks );
return cacheTrim( cache );
}
double
tr_cacheGetLimit( const tr_cache * cache )
{
return cache->maxMiB;
}
tr_cache *
tr_cacheNew( double maxMiB )
{
tr_cache * cache = tr_new0( tr_cache, 1 );
cache->blocks = TR_PTR_ARRAY_INIT;
cache->maxBlocks = getMaxBlocks( maxMiB );
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,
const uint8_t * 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->buf = NULL;
tr_ptrArrayInsertSorted( &cache->blocks, cb, cache_block_compare );
}
cb->time = tr_time();
tr_free( cb->buf );
cb->buf = tr_memdup( writeme, 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 )
memcpy( setme, cb->buf, 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
findPiece( tr_cache * cache, tr_torrent * torrent, tr_piece_index_t piece )
{
struct cache_block key;
key.tor = torrent;
key.block = tr_torPieceFirstBlock( torrent, piece );
return tr_ptrArrayLowerBound( &cache->blocks, &key, cache_block_compare, NULL );
}
int
tr_cacheFlushFile( tr_cache * cache, tr_torrent * torrent, tr_file_index_t i )
{
int err = 0;
const tr_file * file = &torrent->info.files[i];
const tr_block_index_t begin = tr_torPieceFirstBlock( torrent, file->firstPiece );
const tr_block_index_t end = tr_torPieceFirstBlock( torrent, file->lastPiece ) + tr_torPieceCountBlocks( torrent, file->lastPiece );
const int pos = findPiece( cache, torrent, file->firstPiece );
//fprintf( stderr, "flushing file %d, which is blocks [%zu...%zu)\n", (int)i, (size_t)begin, (size_t)end );
/* 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 < begin ) || ( b->block >= end ) ) 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 = findPiece( 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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