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 "log.h"
#include "peer-common.h" /* MAX_BLOCK_SIZE */
#include "ptrarray.h"
#include "torrent.h"
#include "trevent.h"
#include "utils.h"
#define MY_NAME "Cache"
#define dbgmsg(...) \
do \
{ \
if (tr_logGetDeepEnabled ()) \
tr_logAddDeep (__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;
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);
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;
int err = 0;
for (i=0; !err && i<n; i++)
{
int j;
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_logAddNamedDbg (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);
assert (tr_amInEventThread (torrent->session));
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)
{
int i, n;
struct run_info * runs;
runs = tr_new (struct run_info, tr_ptrArraySize (&cache->blocks));
i = 0;
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;
}