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log0log.cc
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log0log.cc
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#include "log0log.h"
#include "mem0mem.h"
#include "buf0buf.h"
#include "buf0flu.h"
#include "srv0srv.h"
#include "log0recv.h"
#include "fil0fil.h"
#include "dict0boot.h"
#include "srv0srv.h"
#include "srv0start.h"
#include "trx0sys.h"
#include "trx0trx.h"
#include <stdint.h>
/*当前free的限制，0表示没有进行初始化*/
ulint log_fsp_current_free_limit = 0;
/*全局log对象*/
log_t* log_sys = NULL;
ibool log_do_write = TRUE;
ibool log_debug_writes = FALSE;
byte log_archive_io;
/*2K*/
#define LOG_BUF_WRITE_MARGIN (4 * OS_FILE_LOG_BLOCK_SIZE)
#define LOG_BUF_FLUSH_RATIO 2
/*2K + 64K*/
#define LOG_BUF_FLUSH_MARGIN (LOG_BUF_WRITE_MARGIN + 4 * UNIV_PAGE_SIZE)
/*64K*/
#define LOG_CHECKPOINT_FREE_PER_THREAD (4 * UNIV_PAGE_SIZE)
/*128K*/
#define LOG_CHECKPOINT_EXTRA_FREE (8 * UNIV_PAGE_SIZE)
/*异步的checkpoint,控制生成一个checkpoint比例*/
#define LOG_POOL_CHECKPOINT_RATIO_ASYNC 32
/*同步flush比例*/
#define LOG_POOL_PREFLUSH_RATIO_SYNC 16
/*异步的flush比例*/
#define LOG_POOL_PREFLUSH_RATIO_ASYNC 8
#define LOG_ARCHIVE_EXTRA_MARGIN (4 * UNIV_PAGE_SIZE)
#define LOG_ARCHIVE_RATIO_ASYNC 16
#define LOG_UNLOCK_NONE_FLUSHED_LOCK 1
#define LOG_UNLOCK_FLUSH_LOCK 2
/*Archive的操作类型*/
#define LOG_ARCHIVE_READ 1
#define LOG_ARCHIVE_WRITE 2
/*完成checkpoint的写io操作*/
static void log_io_complete_checkpoint(log_group_t* group);
/*完成archive的io操作*/
static void log_io_complete_archive();
/*检查archive日志文件归档是否可以触发*/
static void log_archive_margin();
/*设置fsp_current_free_limit,这个改变有可能会产生一个checkpoint*/
void log_fsp_current_free_limit_set_and_checkpoint(ulint limit)
{
ibool success;
mutex_enter(&(log_sys->mutex));
log_fsp_current_free_limit = limit;
mutex_exit(&(log_sys->mutex));
success = FALSE;
while(!success){
success = log_checkpoint(TRUE, TRUE);
}
}
/*获得buf pool当中最老的lsn，如果buf pool中的oldest = 0，默认返回log_sys中的lsn*/
static dulint log_buf_pool_get_oldest_modification()
{
dulint lsn;
ut_ad(mutex_own(&(log_sys->mutex)));
/*buf_pool_get_oldest_modification是buf0buf中，返回buf pool中修改的block当中最旧的lsn*/
lsn = buf_pool_get_oldest_modification();
if(ut_dulint_is_zero(lsn))
lsn = log_sys->lsn;
return lsn;
}
/*打开一个新的block，在打开前，需要判断log->buf的剩余空间和归档的buf空间*/
dulint log_reserve_and_open(ulint len)
{
log_t* log = log_sys;
ulint len_upper_limit;
ulint archived_lsn_age;
ulint count = 0;
ulint dummy;
ut_a(len < log->buf_size / 2);
loop:
mutex_enter(&(log->mutex));
/*计算长度上限*/
len_upper_limit = LOG_BUF_FLUSH_MARGIN + (5 * len) / 4;
if(log->buf_free + len_upper_limit > log->buf_size){/*长度超过了buf_size,需要对log buffer进行flush_up*/
mutex_exit(&(log->mutex));
/*没有足够的空间，同步将log buffer刷入磁盘*/
log_flush_up_to(ut_dulint_max, LOG_WAIT_ALL_GROUPS);
count ++;
ut_ad(count < 50);
goto loop;
}
/*log归档选项是激活的*/
if(log->archiving_state != LOG_ARCH_OFF){
/*计算lsn和archived_lsn的差值*/
archived_lsn_age = ut_dulint_minus(log->lsn, log->archived_lsn);
if(archived_lsn_age + len_upper_limit > log->max_archived_lsn_age){ /*正在存档状态又超过存档的lsn 最大范围*/
mutex_exit(&(log->mutex));
ut_ad(len_upper_limit <= log->max_archived_lsn_age);
/*强制同步进行archive write*/
log_archive_do(TRUE, &dummy);
cout ++;
ut_ad(count < 50);
goto loop;
}
}
#ifdef UNIV_LOG_DEBUG
log->old_buf_free = log->buf_free;
log->old_lsn = log->lsn;
#endif
return log->lsn;
}
void log_write_low(byte* str, ulint str_len)
{
log_t* log = log_sys;
ulint len;
ulint data_len;
byte* log_block;
ut_ad(mutex_own(&(log->mutex)));
part_loop:
/*计算part length*/
data_len = log->buf_free % OS_FILE_LOG_BLOCK_SIZE + str_len;
if(data_len < OS_FILE_LOG_BLOCK_SIZE - LOG_BLOCK_TRL_SIZE) /*可以在同一个block当中*/
len = str_len;
else{
data_len = OS_FILE_LOG_BLOCK_SIZE - LOG_BLOCK_TRL_SIZE;
/*将block相对相对剩余的长度作为len*/
len = OS_FILE_LOG_BLOCK_SIZE - (log->buf_free % OS_FILE_LOG_BLOCK_SIZE) - LOG_BLOCK_TRL_SIZE;
}
/*将日志内容拷贝到log buffer*/
ut_memcpy(log->buf + log->buf_free, str, len);
str_len -= len;
str = str + len;
log_block = ut_align(log->buf + log->buf_free, OS_FILE_LOG_BLOCK_SIZE);
log_block_set_data_len(log_block, data_len);
if(data_len = OS_FILE_LOG_BLOCK_SIZE - LOG_BLOCK_TRL_SIZE){ /*完成一个block的写入*/
log_block_set_data_len(log_block, OS_FILE_LOG_BLOCK_SIZE); /*重新设置长度*/
log_block_set_checkpoint_no(log_block, log_sys->next_checkpoint_no); /*设置checkpoint number*/
len += LOG_BLOCK_HDR_SIZE + LOG_BLOCK_TRL_SIZE;
log->lsn = ut_dulint_add(log->lsn, len);
/*初始化一个新的block*/
log_block_init(log_block + OS_FILE_LOG_BLOCK_SIZE, log->lsn);
}
else /*更改lsn*/
log->lsn = ut_dulint_add(log->lsn, len);
log->buf_free += len;
ut_ad(log->buf_free <= log->buf_size);
if(str_len > 0)
goto part_loop;
}
/*在mtr_commit事务提交的时候调用*/
dulint log_close()
{
byte* log_block;
ulint first_rec_group;
dulint oldest_lsn;
dulint lsn;
log_t* log = log_sys;
ut_ad(mutex_own(&(log->mutex)));
lsn = log->lsn;
/*如果这block的first_rec_group = 0说明first_rec_group没有被设置，设置block的数据长度为其first_rec_group*/
log_block = ut_align_down(log->buf + log->buf_free, OS_FILE_LOG_BLOCK_SIZE);
first_rec_group = log_block_get_first_rec_group(log_block);
if(first_rec_group == 0)
log_block_set_first_rec_group(log_block, log_block_get_data_len(log_block));
/*超过最大的buf free,需要进行flush或者建立checkpoint*/
if(log->buf_free > log->max_buf_free)
log->check_flush_or_checkpoint = TRUE;
/*如果lsn差值还没达到检查点容忍的差值，直接退出函数*/
if(ut_dulint_minus(lsn, log->last_checkpoint_lsn) <= log->max_modified_age_async)
goto function_exit;
oldest_lsn = buf_pool_get_oldest_modification();
/*对lsn的判断，如果oldest_lsn与当前lsn的差值同步的阈值就启动flush或者建立一个checkpoint*/
if(ut_dulint_is_zero(oldest_lsn) || (ut_dulint_minus(lsn, oldest_lsn) > log->max_modified_age_async)
|| (ut_dulint_minus(lsn, log->last_checkpoint_lsn) > log->max_checkpoint_age_async))
log->check_flush_or_checkpoint = TRUE;
function_exit:
#ifdef UNIV_LOG_DEBUG
log_check_log_recs(log->buf + log->old_buf_free, log->buf_free - log->old_buf_free, log->old_lsn);
#endif
return lsn;
}
/*在归档前，填充最后一个block*/
static void log_pad_current_log_block()
{
byte b = MLOG_DUMMY_RECORD;
ulint pad_length;
ulint i;
dulint lsn;
/*尝试开启一个新的block*/
lsn = log_reserve_and_open(OS_FILE_LOG_BLOCK_SIZE);
/*计算可填充的长度并用b进行数据填充*/
pad_length = OS_FILE_LOG_BLOCK_SIZE - (log_sys->buf_free % OS_FILE_LOG_BLOCK_SIZE) - LOG_BLOCK_TRL_SIZE;
for(i = 0; i < pad_length; i++)
log_write_low(&b, 1);
lsn = log_sys->lsn;
log_close();
log_release();
ut_a((ut_dulint_get_low(lsn) % OS_FILE_LOG_BLOCK_SIZE) == LOG_BLOCK_HDR_SIZE);
}
/*获得一个group 可以容纳的日志长度,一个group有相同长度的文件组成*/
ulint log_group_get_capacity(log_group_t* group)
{
ut_ad(mutex_own(&(log_sys->mutex)));
return((group->file_size - LOG_FILE_HDR_SIZE) * group->n_files);
}
/*将group 内部的相对偏移换算绝对偏移换，绝对偏移量 = offset - 文件头长度 */
UNIV_INLINE ulint log_group_calc_size_offset(ulint offset, log_group_t* group)
{
ut_ad(mutex_own(&(log_sys->mutex)));
return offset - LOG_FILE_HDR_SIZE * (1 + offset / group->file_size);
}
/*通过绝对偏移获得在group file里的相对偏移量*/
UNIV_INLINE ulint log_group_calc_real_offset(ulint offset, log_group_t* group)
{
ut_ad(mutex_own(&(log_sys->mutex)));
return (offset + LOG_FILE_HDR_SIZE * (1 + offset / (group->file_size - LOG_FILE_HDR_SIZE)));
}
/*返回lsn相对group起始位置的相对位置*/
static ulint log_group_calc_lsn_offset(dulint lsn, log_group_t* group)
{
dulint gr_lsn;
int64_t gr_lsn_size_offset;
int64_t difference;
int64_t group_size;
int64_t offset;
ut_ad(mutex_own(&(log_sys->mutex)));
gr_lsn = group->lsn;
/*获得lsn_offset绝对偏移,去除文件头长度*/
gr_lsn_size_offset = (int64_t)(log_group_calc_size_offset(group->lsn_offset, group));
/*获得group的容量*/
group_size = log_group_get_capacity(group);
/*计算grl_lsn和lsn之间的差值绝对值*/
if(ut_dulint_cmp(lsn, gr_lsn) >= 0){
difference = (int64_t) ut_dulint_minus(lsn, gr_lsn);
}
else{
difference = (int64_t)ut_dulint_minus(gr_lsn, lsn);
difference = difference % group_size;
difference = group_size - difference;
}
/*获得相对group size的偏移量*/
offset = (gr_lsn_size_offset + difference) % group_size;
ut_a(offset <= 0xFFFFFFFF);
/*返回相对的位置,加上文件头长度*/
return log_group_calc_real_offset(offset, group);
}
/*获得lsn对应group的文件编号和在文件中对相对起始位置*/
ulint log_calc_where_lsn_is(int64_t* log_file_offset, dulint first_header_lsn, dulint lsn, ulint n_log_files, int64_t log_file_size)
{
int64_t ib_lsn;
int64_t ib_first_header_lsn;
int64_t capacity = log_file_size - LOG_FILE_HDR_SIZE; /*单个group文件可以容纳的数据长度*/
ulint file_no;
int64_t add_this_many;
ib_lsn = ut_conv_dulint_to_longlong(lsn);
ib_first_header_lsn = ut_conv_dulint_to_longlong(first_header_lsn);
if(ib_lsn < ib_first_header_lsn){
add_this_many = 1 + (ib_first_header_lsn - ib_lsn) / (capacity * (int64_t)n_log_files);
ib_lsn += add_this_many * capacity * (int64_t)n_log_files;
}
ut_a(ib_lsn >= ib_first_header_lsn);
file_no = ((ulint)((ib_lsn - ib_first_header_lsn) / capacity)) % n_log_files; /*获得文件的序号*/
/*计算除去group header的位置*/
*log_file_offset = (ib_lsn - ib_first_header_lsn) % capacity;
/*计算相对于文件其实位置的位置*/
*log_file_offset = *log_file_offset + LOG_FILE_HDR_SIZE;
return file_no;
}
void log_group_set_fields(log_group_t* group, dulint lsn)
{
/*获得最新的相对偏移量,加上了LOG_FILE_HDR_SIZE的位置*/
group->lsn_offset = log_group_calc_lsn_offset(lsn, group);
/*设置新的lsn值*/
group->lsn = lsn;
}
/*计算日志刷盘、建立checkpoint和归档的触发阈值*/
static ibool log_calc_max_ages()
{
log_group_t* group;
ulint n_threads;
ulint margin;
ulint free;
ulint smallest_capacity;
ulint archive_margin;
ulint smallest_archive_margin;
ibool success = TRUE;
ut_ad(!mutex_own(&(log_sys->mutex)));
/*获得服务的线程数*/
n_threads = srv_get_n_threads();
mutex_enter(&(log_sys->mutex));
group = UT_LIST_GET_FIRST(log_sys->log_groups);
ut_ad(group);
smallest_capacity = ULINT_MAX;
smallest_archive_margin = ULINT_MAX;
/*重新计算smallest_capacity和smallest_archive_margin*/
while(group){
/*重新评估最小的group能容纳的数据*/
if(log_group_get_capacity(group) < smallest_capacity)
smallest_capacity = log_group_get_capacity(group);
/*归档的margin是group的容量 减去一个group file的大小 再预留64K*/
archive_margin = log_group_get_capacity(group) - (group->file_size - LOG_FILE_HDR_SIZE) - LOG_ARCHIVE_EXTRA_MARGIN;
if(archive_margin < smallest_archive_margin)
smallest_archive_margin = archive_margin;
group = UT_LIST_GET_NEXT(log_groups, group);
}
/*为每个线程预留64K的空间*/
free = LOG_CHECKPOINT_FREE_PER_THREAD * n_threads + LOG_CHECKPOINT_EXTRA_FREE;
if(free >= smallest_capacity / 2){
success = FALSE;
goto failure;
}
else
margin = smallest_capacity - free;
margin = ut_min(margin, log_sys->adm_checkpoint_interval);
/*计算日志写盘的阈值*/
log_sys->max_modified_age_async = margin - margin / LOG_POOL_PREFLUSH_RATIO_ASYNC; /*modified剩余1/8作为异步阈值*/
log_sys->max_modified_age_sync = margin - margin / LOG_POOL_PREFLUSH_RATIO_SYNC; /*modified剩余1/16作为同步阈值*/
log_sys->max_checkpoint_age_async = margin - margin / LOG_POOL_CHECKPOINT_RATIO_ASYNC; /*checkpoint剩余1/32作为异步阈值*/
log_sys->max_checkpoint_age = margin; /*无任何剩余作为强制同步checkpoint阈值*/
log_sys->max_archived_lsn_age = smallest_archive_margin;
log_sys->max_archived_lsn_age_async = smallest_archive_margin - smallest_archive_margin / LOG_ARCHIVE_RATIO_ASYNC;
failure:
mutex_exit(&(log_sys->mutex));
if(!success)
fprintf(stderr, "Error: log file group too small for the number of threads\n");
return success;
}
/*初始化log_sys,在引擎初始化的时候调用*/
void log_init()
{
byte* buf;
log_sys = mem_alloc(sizeof(log_t));
/*建立latch对象*/
mutex_create(&(log_sys->mutex));
mutex_set_level(&(log_sys->mutex), SYNC_LOG);
mutex_enter(&(log_sys->mutex));
log_sys->lsn = LOG_START_LSN;
ut_a(LOG_BUFFER_SIZE >= 16 * OS_FILE_LOG_BLOCK_SIZE);
ut_a(LOG_BUFFER_SIZE >= 4 * UNIV_PAGE_SIZE);
/*为了512字节对齐，所以在开辟内存的时候一定要大于512,buf的长度为log_buff_size个page的长度*/
buf = ut_malloc(LOG_BUFFER_SIZE + OS_FILE_LOG_BLOCK_SIZE);
/*512字节对齐*/
log_sys->buf = ut_align(buf, OS_FILE_LOG_BLOCK_SIZE);
log_sys->buf_size = LOG_BUFFER_SIZE;
memset(log_sys->buf, 0, LOG_BUFFER_SIZE);
log_sys->max_buf_free = log_sys->buf_size / LOG_BUF_FLUSH_RATIO - LOG_BUF_FLUSH_MARGIN;
log_sys->check_flush_or_checkpoint = TRUE;
UT_LIST_INIT(log_sys->log_groups);
log_sys->n_log_ios = 0;
log_sys->n_log_ios_old = log_sys->n_log_ios;
log_sys->last_printout_time = time(NULL);
log_sys->buf_next_to_write = 0;
/*flush lsn设置为0*/
log_sys->flush_lsn = ut_dulint_zero;
log_sys->written_to_some_lsn = log_sys->lsn;
log_sys->written_to_all_lsn = log_sys->lsn;
log_sys->n_pending_writes = 0;
log_sys->no_flush_event = os_event_create(NULL);
os_event_set(log_sys->no_flush_event);
log_sys->one_flushed_event = os_event_create(NULL);
os_event_set(log_sys->one_flushed_event);
log_sys->adm_checkpoint_interval = ULINT_MAX;
log_sys->next_checkpoint_no = ut_dulint_zero;
log_sys->last_checkpoint_lsn = log_sys->lsn;
log_sys->n_pending_checkpoint_writes = 0;
rw_lock_create(&(log_sys->checkpoint_lock));
rw_lock_set_level(&(log_sys->checkpoint_lock), SYNC_NO_ORDER_CHECK);
/*存储checkpoint信息的buf, 一个OS_FILE_LOG_BLOCK_SIZE长度即可*/
log_sys->checkpoint_buf = ut_align(mem_alloc(2 * OS_FILE_LOG_BLOCK_SIZE), OS_FILE_LOG_BLOCK_SIZE);
memset(log_sys->checkpoint_buf, 0, OS_FILE_LOG_BLOCK_SIZE);
log_sys->archiving_state = LOG_ARCH_ON;
log_sys->archived_lsn = log_sys->lsn;
log_sys->next_archived_lsn = ut_dulint_zero;
log_sys->n_pending_archive_ios = 0;
rw_lock_create(&(log_sys->archive_lock));
rw_lock_set_level(&(log_sys->archive_lock), SYNC_NO_ORDER_CHECK);
/*构建archive buf*/
log_sys->archive_buf = ut_align(ut_malloc(LOG_ARCHIVE_BUF_SIZE + OS_FILE_LOG_BLOCK_SIZE), OS_FILE_LOG_BLOCK_SIZE);
log_sys->archive_buf_size = LOG_ARCHIVE_BUF_SIZE;
memset(log_sys->archive_buf, '\0', LOG_ARCHIVE_BUF_SIZE);
log_sys->archiving_on = os_event_create(NULL);
log_sys->online_backup_state = FALSE;
/*初始化第一个block*/
log_block_init(log_sys->buf, log_sys->lsn);
log_block_set_first_rec_group(log_sys->buf, LOG_BLOCK_HDR_SIZE);
/*设置初始化偏移量和其实位置*/
log_sys->buf_free = LOG_BLOCK_HDR_SIZE;
log_sys->lsn = ut_dulint_add(LOG_START_LSN, LOG_BLOCK_HDR_SIZE);
mutex_exit(&(log_sys->mutex));
#ifdef UNIV_LOG_DEBUG
recv_sys_create();
recv_sys_init(FALSE, buf_pool_get_curr_size());
recv_sys->parse_start_lsn = log_sys->lsn;
recv_sys->scanned_lsn = log_sys->lsn;
recv_sys->scanned_checkpoint_no = 0;
recv_sys->recovered_lsn = log_sys->lsn;
recv_sys->limit_lsn = ut_dulint_max;
#endif
}
/*在数据库创创建的时候调用*/
void log_group_init(ulint id, ulint n_files, ulint file_size, ulint space_id, ulint archive_space_id)
{
ulint i;
log_group_t* group;
group = mem_alloc(sizeof(log_group_t));
group->id = id;
group->n_files = n_files;
group->file_size = file_size;
group->space_id = space_id; /*保存重做日志的fil_space*/
group->state = LOG_GROUP_OK;
group->lsn = LOG_START_LSN;
group->lsn_offset = LOG_FILE_HDR_SIZE;
group->n_pending_writes = 0;
group->file_header_bufs = mem_alloc(sizeof(byte*) * n_files);
group->archive_file_header_bufs = mem_alloc(sizeof(byte*) * n_files);
for(i = 0; i < n_files; i ++){
*(group->file_header_bufs + i) = ut_align(mem_alloc(LOG_FILE_HDR_SIZE + OS_FILE_LOG_BLOCK_SIZE), OS_FILE_LOG_BLOCK_SIZE);
memset(*(group->file_header_bufs + i), 0, LOG_FILE_HDR_SIZE);
*(group->archive_file_header_bufs + i) = ut_align(mem_alloc(LOG_FILE_HDR_SIZE + OS_FILE_LOG_BLOCK_SIZE), OS_FILE_LOG_BLOCK_SIZE);
memset(*(group->archive_file_header_bufs + i), 0, LOG_FILE_HDR_SIZE);
}
group->archive_space_id = archive_space_id; /*保存归档日志的fil_space*/
group->archived_file_no = 0;
group->archived_offset = 0;
group->checkpoint_buf = ut_align(mem_alloc(2 * OS_FILE_LOG_BLOCK_SIZE), OS_FILE_LOG_BLOCK_SIZE);
memset(group->checkpoint_buf, 0, OS_FILE_LOG_BLOCK_SIZE);
UT_LIST_ADD_LAST(log_groups, log_sys->log_groups, group);
ut_a(log_calc_max_ages());
}
/*触发unlock信号在io flush完成之后*/
UNIV_INLINE void log_flush_do_unlocks(ulint code)
{
ut_ad(mutex_own(&(log_sys->mutex)));
/*触发one_flushed_event*/
if(code & LOG_UNLOCK_NONE_FLUSHED_LOCK)
os_event_set(log_sys->one_flushed_event);
if(code & LOG_UNLOCK_FLUSH_LOCK)
os_event_set(log_sys->no_flush_event);
}
/*检查group 的io flush是否完成,更改将flush_lsn设置为written_to_some_lsn*/
UNIV_INLINE ulint log_group_check_flush_completion(log_group_t* group)
{
ut_ad(mutex_own(&(log_sys->mutex)));
/*本group已经没有IO操作在进行*/
if(!log_sys->one_flushed && group->n_pending_writes == 0){
if(log_debug_writes)
printf("Log flushed first to group %lu\n", group->id);
log_sys->written_to_some_lsn = log_sys->flush_lsn;
log_sys->one_flushed = TRUE;
return LOG_UNLOCK_NONE_FLUSHED_LOCK;
}
if(log_debug_writes && group->n_pending_writes == 0)
printf("Log flushed to group %lu\n", group->id);
return 0;
}
static ulint log_sys_check_flush_completion()
{
ulint move_start;
ulint move_end;
ut_ad(mutex_own(&(log_sys->mutex)));
/*整个log_sys没有io操作在进行*/
if(log_sys->n_pending_writes == 0){
log_sys->written_to_all_lsn = log_sys->flush_lsn;
log_sys->buf_next_to_write = log_sys->flush_end_offset; /*下次进行log flush操作数据起始偏移*/
/*数据向前移，因为全面的数据已经flush到磁盘*/
if(log_sys->flush_end_offset > log_sys->max_buf_free / 2){
/*确定移动的位置*/
move_start = ut_calc_align_down(log_sys->flush_end_offset, OS_FILE_LOG_BLOCK_SIZE);
move_end = ut_calc_align(log_sys->buf_free, OS_FILE_LOG_BLOCK_SIZE);
ut_memmove(log_sys->buf, log_sys->buf + move_start, move_end - move_start);
/*重新设置buf_free和buf_next_to_write*/
log_sys->buf_free -= move_start;
log_sys->buf_next_to_write -= move_start;
}
return(LOG_UNLOCK_FLUSH_LOCK);
}
return 0;
}
/*完成group的io操作*/
void log_io_complete(log_group_t* group)
{
ulint unlock;
/*一个日志归档类完成io操作,归档IO操作会将log_archive_io传入aio控制模块*/
if((byte*)group == &log_archive_io){
log_io_complete_archive();
return;
}
/*一个checkpoint IO,在checkpoint fil_io传入的group指针加了1，这样做的目的应该是区分checkpoint io和日志文件IO*/
if((ulint)group & 0x1){
group = (log_group_t*)((ulint)group - 1);
/*将file0file中的space写入到硬盘*/
if (srv_unix_file_flush_method != SRV_UNIX_O_DSYNC && srv_unix_file_flush_method != SRV_UNIX_NOSYNC)
fil_flush(group->space_id);
log_io_complete_checkpoint(group);
return;
}
ut_a(0); /*innodb都是采用同步写的方式写日志，一般不会到下面的代码中*/
if(srv_unix_file_flush_method != SRV_UNIX_O_DSYNC && srv_unix_file_flush_method != SRV_UNIX_NOSYNC && srv_flush_log_at_trx_commit != 2)
{
fil_flush(group->space_id);
}
mutex_enter(&(log_sys->mutex));
ut_a(group->n_pending_writes > 0);
ut_a(log_sys->n_pending_writes > 0);
group->n_pending_writes--;
log_sys->n_pending_writes--;
/*对单个group的状态做更新*/
unlock = log_group_check_flush_completion(group);
/*对sys_log状态做更新*/
unlock = unlock | log_sys_check_flush_completion();
/*触发io flush完成的信号*/
log_flush_do_unlocks(unlock);
mutex_exit(&(log_sys->mutex));
}
/*在Master thread中每秒调用一次,主要功能是对日志进行flush*/
void log_flush_to_disk()
{
log_group_t* group;
loop:
mutex_enter(&(log_sys->mutex));
/*有fil_flush正在执行,等待所有正在进行的fil_flush结束*/
if(log_sys->n_pending_writes > 0){
mutex_exit(&(log_sys->mutex));
/*进入等待状态*/
os_event_wait(log_sys->no_flush_event);
goto loop;
}
group = UT_LIST_GET_FIRST(log_sys->log_groups);
/*进行space刷盘时，防止其他线程同时进行*/
log_sys->n_pending_writes ++;
group->n_pending_writes ++;
/*让其他刷盘行为等待，例如：checkpoint*/
os_event_reset(log_sys->no_flush_event);
os_event_reset(log_sys->one_flushed_event);
mutex_exit(&(log_sys->mutex));
/*log文件刷盘*/
fil_flush(group->space_id);
mutex_enter(&(log_sys->mutex));
ut_a(group->n_pending_writes == 1);
ut_a(log_sys->n_pending_writes == 1);
/*刷盘完成，pending回到完成的状态，以便log_io_complete进行判断*/
group->n_pending_writes--;
log_sys->n_pending_writes--;
os_event_set(log_sys->no_flush_event);
os_event_set(log_sys->one_flushed_event);
mutex_exit(&(log_sys->mutex));
}
/*将group header写入到log file的page cache当中*/
static void log_group_file_header_flush(ulint type, log_group_t* group, ulint nth_file, dulint start_lsn)
{
byte* buf;
ulint dest_offset;
ut_ad(mutex_own(&(log_sys->mutex)));
ut_a(nth_file < group->n_files);
/*找到文件对应goup中的头缓冲区*/
buf = *(group->file_header_bufs + nth_file);
/*写入group id*/
mach_write_to_4(buf + LOG_GROUP_ID, group->id);
/*写入起始的lsn*/
mach_write_to_8(buf + LOG_FILE_START_LSN, start_lsn);
/*第12 ~ 第16个字节是存储file no*/
memcpy(buf + LOG_FILE_WAS_CREATED_BY_HOT_BACKUP, " ", 4);
dest_offset = nth_file * group->file_size;
if(log_debug_writes)
printf("Writing log file header to group %lu file %lu\n", group->id, nth_file);
if(log_do_write){
log_sys->n_log_ios++;
/*调用异步io进行文件写入,同步写入*/
fil_io(OS_FILE_WRITE | OS_FILE_LOG, TRUE, group->space_id, dest_offset / UNIV_PAGE_SIZE, dest_offset % UNIV_PAGE_SIZE, OS_FILE_LOG_BLOCK_SIZE,
buf, group);
}
}
/*设置block的check sum*/
static void log_block_store_checksum(byte* block)
{
log_block_set_checksum(block, log_block_calc_checksum(block));
}
void log_group_write_buf(ulint type, log_group_t* group, byte* buf, ulint len, dulint start_lsn, ulint new_data_offset)
{
ulint write_len;
ibool write_header;
ulint next_offset;
ulint i;
ut_ad(mutex_own(&(log_sys->mutex)));
ut_a(len % OS_FILE_LOG_BLOCK_SIZE == 0);
ut_a(ut_dulint_get_low(start_lsn) % OS_FILE_LOG_BLOCK_SIZE == 0);
if(new_data_offset == 0)
write_header = TRUE;
else
write_header = FALSE;
loop:
if(len == 0)
return ;
next_offset = log_group_calc_lsn_offset(start_lsn, group);
if((next_offset % group->file_size == LOG_FILE_HDR_SIZE) && write_header){ /*可以进行group header头信息写log file*/
log_group_file_header_flush(type, group, next_offset / group->file_size, start_lsn);
}
/*一个文件存储不下，分片存储*/
if((next_offset % group->file_size) + len > group->file_size) /*计算本次分片存储的大小*/
write_len = group->file_size - (next_offset % group->file_size);
else
write_len = len;
if(log_debug_writes){
printf("Writing log file segment to group %lu offset %lu len %lu\n"
"start lsn %lu %lu\n",
group->id, next_offset, write_len,
ut_dulint_get_high(start_lsn),
ut_dulint_get_low(start_lsn));
printf("First block n:o %lu last block n:o %lu\n",
log_block_get_hdr_no(buf),
log_block_get_hdr_no(buf + write_len - OS_FILE_LOG_BLOCK_SIZE));
ut_a(log_block_get_hdr_no(buf) == log_block_convert_lsn_to_no(start_lsn));
for(i = 0; i < write_len / OS_FILE_LOG_BLOCK_SIZE; i ++){
ut_a(log_block_get_hdr_no(buf) + i == log_block_get_hdr_no(buf + i * OS_FILE_LOG_BLOCK_SIZE));
}
}
/*计算各个block的check sum， write_len一定是512的整数倍*/
for(i = 0; i < write_len / OS_FILE_LOG_BLOCK_SIZE; i ++)
log_block_store_checksum(buf + i * OS_FILE_LOG_BLOCK_SIZE);
for(log_do_write){
log_sys->n_log_ios ++;
/*将block刷入磁盘*/
fil_io(OS_FILE_WRITE | OS_FILE_LOG, TRUE, group->space_id, next_offset / UNIV_PAGE_SIZE, next_offset % UNIV_PAGE_SIZE, write_len, buf, group);
}
if(write_len < len){
/*更改start lsn*/
start_lsn = ut_dulint_add(start_lsn, write_len);
len -= write_len;
buf += write_len;
write_header = TRUE;
goto loop;
}
}
/*一般是刷log_write_low来的日志*/
void log_flush_up_to(dulint lsn, ulint wait)
{
log_group_t* group;
ulint start_offset;
ulint end_offset;
ulint area_start;
ulint area_end;
ulint loop_count;
ulint unlock;
/*没有ibuf log操作或者正在恢复数据库*/
if(recv_no_ibuf_operations)
return ;
loop_count;
loop:
loop_count ++;
ut_ad(loop_count < 5);
if(loop_count > 2){
printf("Log loop count %lu\n", loop_count);
}
mutex_enter(&(log_sys->mutex));
/*lsn <= 已经刷盘的lsn,表示没有数据需要刷盘*/
if ((ut_dulint_cmp(log_sys->written_to_all_lsn, lsn) >= 0)
|| ((ut_dulint_cmp(log_sys->written_to_some_lsn, lsn) >= 0) && (wait != LOG_WAIT_ALL_GROUPS))) {
mutex_exit(&(log_sys->mutex));
return;
}
/*正在log_sys有fil_flush IO操作*/
if(log_sys->n_pending_writes > 0){
if(ut_dulint_cmp(log_sys->flush_lsn, lsn) >= 0)
goto do_waits;
mutex_exit(&(log_sys->mutex));
/*进入no flush event等待*/
os_event_wait(log_sys->no_flush_event);
goto loop;
}
/*缓冲区中无数据刷盘*/
if(log_sys->buf_free == log_sys->buf_next_to_write){
mutex_exit(&(log_sys->mutex));
return;
}
if(log_debug_writes){
printf("Flushing log from %lu %lu up to lsn %lu %lu\n",
ut_dulint_get_high(log_sys->written_to_all_lsn),
ut_dulint_get_low(log_sys->written_to_all_lsn),
ut_dulint_get_high(log_sys->lsn),
ut_dulint_get_low(log_sys->lsn));
}
log_sys->n_pending_writes++;
group = UT_LIST_GET_FIRST(log_sys->log_groups);
group->n_pending_writes++;
/*重置信号，以便对这两个信号进行监视*/
os_event_reset(log_sys->no_flush_event);
os_event_reset(log_sys->one_flushed_event);
/*计算需要flush的位置范围*/
start_offset = log_sys->buf_next_to_write;
end_offset = log_sys->buf_free;
area_start = ut_calc_align_down(start_offset, OS_FILE_LOG_BLOCK_SIZE);
area_end = ut_calc_align(end_offset, OS_FILE_LOG_BLOCK_SIZE);
ut_ad(area_end - area_start > 0);
/*设置最后flush的lsn*/
log_sys->flush_lsn = log_sys->lsn;
log_sys->one_flushed = FALSE;
/*设置flush的标识位*/
log_block_set_flush_bit(log_sys->buf + area_start, TRUE);
/*在最后一块设置了checkpoint no*/
log_block_set_checkpoint_no(log_sys->buf + area_end - OS_FILE_LOG_BLOCK_SIZE, log_sys->next_checkpoint_no);
/*为什么将最后一个block向后移动,有可能最后一个block并没有满，防止下次写不会写在最后flush的这个块上，因为buf_free 和flush_end_offset做了增长？？*/
ut_memcpy(log_sys->buf + area_end, log_sys->buf + area_end - OS_FILE_LOG_BLOCK_SIZE, OS_FILE_LOG_BLOCK_SIZE);
log_sys->buf_free += OS_FILE_LOG_BLOCK_SIZE;
log_sys->flush_end_offset = log_sys->buf_free;
/*将各个group buf刷入到磁盘*/
group = UT_LIST_GET_FIRST(log_sys->log_groups);
while(group){
/*将group buf刷入到log文件中*/
log_group_write_buf(LOG_FLUSH, group, log_sys->buf + area_start, area_end - area_start,
ut_dulint_align_down(log_sys->written_to_all_lsn, OS_FILE_LOG_BLOCK_SIZE), start_offset - area_start);
/*设置新的group->lsn*/
log_group_set_fields(group, log_sys->flush_lsn);
group = UT_LIST_GET_NEXT(log_groups, group);
}
mutex_exit(&(log_sys->mutex));
/*srv_flush_log_at_trx_commit =2的话，日志只是在PAGE CACHE当中，如果服务器断电重启，日志就丢了*/
if (srv_unix_file_flush_method != SRV_UNIX_O_DSYNC && srv_unix_file_flush_method != SRV_UNIX_NOSYNC && srv_flush_log_at_trx_commit != 2) {
group = UT_LIST_GET_FIRST(log_sys->log_groups);
fil_flush(group->space_id);
}
mutex_enter(&(log_sys->mutex));
group = UT_LIST_GET_FIRST(log_sys->log_groups);
ut_a(group->n_pending_writes == 1);
ut_a(log_sys->n_pending_writes == 1);
group->n_pending_writes--;
log_sys->n_pending_writes--;
/*检测io是否完成*/
unlock = log_group_check_flush_completion(group);
unlock = unlock | log_sys_check_flush_completion();
log_flush_do_unlocks(unlock);
mutex_exit(log_sys->mutex);
return;
do_waits:
mutex_exit(&(log_sys->mutex));
/*等待操作完成的信号*/
if(wait == LOG_WAIT_ONE_GROUP)
os_event_wait(log_sys->one_flushed_event);
else if(wait == LOG_WAIT_ALL_GROUPS)
os_event_wait(log_sys->no_flush_event);
else
ut_ad(wait == LOG_NO_WAIT);
}
static void log_flush_margin()
{
ibool do_flush = FALSE;
log_t* log = log_sys;
mutex_enter(&(log->mutex));
if(log->buf_free > log->max_buf_free){ /*已经超过了容忍的最大位置，必须进行强制刷盘*/
if(log->n_pending_writes > 0){ /*已经有fil_flush在刷盘*/
}
else
do_flush = TRUE;
}
mutex_exit(&(log->mutex));
if(do_flush) /*强制将log_sys刷盘*/
log_flush_up_to(ut_dulint_max, LOG_NO_WAIT);
}
/********************************************************************
Advances the smallest lsn for which there are unflushed dirty blocks in the
buffer pool. NOTE: this function may only be called if the calling thread owns
no synchronization objects! */
ibool log_preflush_pool_modified_pages(dulint new_oldest, ibool sync)
{
ulint n_pages;
if(recv_recovery_on){ /*正在进行数据恢复，必须将所有的记录的log加入到他们搁置的file page里面要获得正确的lsn*/
recv_apply_hashed_log_recs(TRUE);
}
n_pages = buf_flush_batch(BUF_FLUSH_LIST, ULINT_MAX, new_oldest);
if(sync)
buf_flush_wait_batch_end(BUF_FLUSH_LIST);
return (n_pages == ULINT_UNDEFINED) ? FALSE : TRUE;
}
static void log_complete_checkpoint()
{
ut_ad(mutex_own(&(log_sys->mutex)));
ut_ad(log_sys->n_pending_checkpoint_writes == 0);
/*checkpoint ++*/
log_sys->next_checkpoint_no = ut_dulint_add(log_sys->next_checkpoint_no, 1);
/*更改last checkpoint lsn*/
log_sys->last_checkpoint_lsn = log_sys->next_checkpoint_lsn;
/*释放独占的checkpoint_lock*/
rw_lock_x_unlock_gen(&(log_sys->checkpoint_lock), LOG_CHECKPOINT);
}