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Bug 12356373 - PERFORMANCE REGRESSION FROM 5.1 TO 5.5 : GROUP BY:

Browse Source 
The title of the bug is a little confusing. The actual fix is to
reintroduce random readahead inside InnoDB with a dynamic, global
switch innodb_random_read_ahead [default = off].

Approved by: Sunny Bains
rb://696
This commit is contained in:
Inaam Rana 2011-07-19 10:37:37 -04:00
parent 0f543e8e9d
commit aa3d29681e
8 changed files with 232 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
storage/innodb_plugin/ChangeLog
View File

@ -1,3 +1,10 @@
2011-07-19 The InnoDB Team
* buf/buf0buf.c, buf/buf0rea.c, handler/ha_innodb.cc,
include/buf0buf.h, include/buf0buf.ic, include/srv0srv.h,
srv/srv0srv.c:
Fix bug#Bug 12356373 by reintroducing random readahead
2011-06-30 The InnoDB Team
* row/row0row.c:

6
storage/innodb_plugin/buf/buf0buf.c
View File

@ -3590,12 +3590,16 @@ buf_print_io(
/* Statistics about read ahead algorithm */
fprintf(file, "Pages read ahead %.2f/s,"
" evicted without access %.2f/s\n",
" evicted without access %.2f/s,"
" Random read ahead %.2f/s\n",
(buf_pool->stat.n_ra_pages_read
- buf_pool->old_stat.n_ra_pages_read)
/ time_elapsed,
(buf_pool->stat.n_ra_pages_evicted
- buf_pool->old_stat.n_ra_pages_evicted)
/ time_elapsed,
(buf_pool->stat.n_ra_pages_read_rnd
- buf_pool->old_stat.n_ra_pages_read_rnd)
/ time_elapsed);
/* Print some values to help us with visualizing what is

170
storage/innodb_plugin/buf/buf0rea.c
View File

@ -38,6 +38,14 @@ Created 11/5/1995 Heikki Tuuri
#include "srv0start.h"
#include "srv0srv.h"
/** The size in blocks of the area where the random read-ahead algorithm counts
the accessed pages when deciding whether to read-ahead */
#define BUF_READ_AHEAD_RANDOM_AREA BUF_READ_AHEAD_AREA
/** There must be at least this many pages in buf_pool in the area to start
a random read-ahead */
#define BUF_READ_AHEAD_RANDOM_THRESHOLD (5 + BUF_READ_AHEAD_RANDOM_AREA / 8)
/** The linear read-ahead area size */
#define BUF_READ_AHEAD_LINEAR_AREA BUF_READ_AHEAD_AREA
@ -157,6 +165,165 @@ buf_read_page_low(
return(1);
}
/********************************************************************//**
Applies a random read-ahead in buf_pool if there are at least a threshold
value of accessed pages from the random read-ahead area. Does not read any
page, not even the one at the position (space, offset), if the read-ahead
mechanism is not activated. NOTE 1: the calling thread may own latches on
pages: to avoid deadlocks this function must be written such that it cannot
end up waiting for these latches! NOTE 2: the calling thread must want
access to the page given: this rule is set to prevent unintended read-aheads
performed by ibuf routines, a situation which could result in a deadlock if
the OS does not support asynchronous i/o.
@return number of page read requests issued; NOTE that if we read ibuf
pages, it may happen that the page at the given page number does not
get read even if we return a positive value! */
static
ulint
buf_read_ahead_random(
/*==================*/
ulint space, /*!< in: space id */
ulint zip_size,/*!< in: compressed page size in bytes, or 0 */
ulint offset) /*!< in: page number of a page which the current thread
wants to access */
{
ib_int64_t tablespace_version;
ulint recent_blocks = 0;
ulint count;
ulint ibuf_mode;
ulint low, high;
ulint err;
ulint i;
ulint buf_read_ahead_random_area;
if (!srv_random_read_ahead) {
/* Disabled by user */
return(0);
}
if (srv_startup_is_before_trx_rollback_phase) {
/* No read-ahead to avoid thread deadlocks */
return(0);
}
if (ibuf_bitmap_page(zip_size, offset)
|| trx_sys_hdr_page(space, offset)) {
/* If it is an ibuf bitmap page or trx sys hdr, we do
no read-ahead, as that could break the ibuf page access
order */
return(0);
}
/* Remember the tablespace version before we ask the tablespace size
below: if DISCARD + IMPORT changes the actual .ibd file meanwhile, we
do not try to read outside the bounds of the tablespace! */
tablespace_version = fil_space_get_version(space);
buf_read_ahead_random_area = BUF_READ_AHEAD_RANDOM_AREA;
low = (offset / buf_read_ahead_random_area)
* buf_read_ahead_random_area;
high = (offset / buf_read_ahead_random_area + 1)
* buf_read_ahead_random_area;
if (high > fil_space_get_size(space)) {
high = fil_space_get_size(space);
}
buf_pool_mutex_enter();
if (buf_pool->n_pend_reads
> buf_pool->curr_size / BUF_READ_AHEAD_PEND_LIMIT) {
buf_pool_mutex_exit();
return(0);
}
/* Count how many blocks in the area have been recently accessed,
that is, reside near the start of the LRU list. */
for (i = low; i < high; i++) {
const buf_page_t* bpage = buf_page_hash_get(space, i);
if (bpage
&& buf_page_is_accessed(bpage)
&& buf_page_peek_if_young(bpage)) {
recent_blocks++;
if (recent_blocks >= BUF_READ_AHEAD_RANDOM_THRESHOLD) {
buf_pool_mutex_exit();
goto read_ahead;
}
}
}
buf_pool_mutex_exit();
/* Do nothing */
return(0);
read_ahead:
/* Read all the suitable blocks within the area */
if (ibuf_inside()) {
ibuf_mode = BUF_READ_IBUF_PAGES_ONLY;
} else {
ibuf_mode = BUF_READ_ANY_PAGE;
}
count = 0;
for (i = low; i < high; i++) {
/* It is only sensible to do read-ahead in the non-sync aio
mode: hence FALSE as the first parameter */
if (!ibuf_bitmap_page(zip_size, i)) {
count += buf_read_page_low(
&err, FALSE,
ibuf_mode | OS_AIO_SIMULATED_WAKE_LATER,
space, zip_size, FALSE,
tablespace_version, i);
if (err == DB_TABLESPACE_DELETED) {
ut_print_timestamp(stderr);
fprintf(stderr,
" InnoDB: Warning: in random"
" readahead trying to access\n"
"InnoDB: tablespace %lu page %lu,\n"
"InnoDB: but the tablespace does not"
" exist or is just being dropped.\n",
(ulong) space, (ulong) i);
}
}
}
/* In simulated aio we wake the aio handler threads only after
queuing all aio requests, in native aio the following call does
nothing: */
os_aio_simulated_wake_handler_threads();
#ifdef UNIV_DEBUG
if (buf_debug_prints && (count > 0)) {
fprintf(stderr,
"Random read-ahead space %lu offset %lu pages %lu\n",
(ulong) space, (ulong) offset,
(ulong) count);
}
#endif /* UNIV_DEBUG */
/* Read ahead is considered one I/O operation for the purpose of
LRU policy decision. */
buf_LRU_stat_inc_io();
buf_pool->stat.n_ra_pages_read_rnd += count;
return(count);
}
/********************************************************************//**
High-level function which reads a page asynchronously from a file to the
buffer buf_pool if it is not already there. Sets the io_fix flag and sets
@ -175,6 +342,9 @@ buf_read_page(
ulint count;
ulint err;
count = buf_read_ahead_random(space, zip_size, offset);
srv_buf_pool_reads += count;
tablespace_version = fil_space_get_version(space);
/* We do the i/o in the synchronous aio mode to save thread

8
storage/innodb_plugin/handler/ha_innodb.cc
View File

@ -501,6 +501,8 @@ static SHOW_VAR innodb_status_variables[]= {
(char*) &export_vars.innodb_buffer_pool_pages_misc, SHOW_LONG},
{"buffer_pool_pages_total",
(char*) &export_vars.innodb_buffer_pool_pages_total, SHOW_LONG},
{"buffer_pool_read_ahead_rnd",
(char*) &export_vars.innodb_buffer_pool_read_ahead_rnd, SHOW_LONG},
{"buffer_pool_read_ahead",
(char*) &export_vars.innodb_buffer_pool_read_ahead, SHOW_LONG},
{"buffer_pool_read_ahead_evicted",
@ -11027,6 +11029,11 @@ static MYSQL_SYSVAR_UINT(change_buffering_debug, ibuf_debug,
NULL, NULL, 0, 0, 1, 0);
#endif /* UNIV_DEBUG || UNIV_IBUF_DEBUG */
static MYSQL_SYSVAR_BOOL(random_read_ahead, srv_random_read_ahead,
PLUGIN_VAR_NOCMDARG,
"Whether to use read ahead for random access within an extent.",
NULL, NULL, FALSE);
static MYSQL_SYSVAR_ULONG(read_ahead_threshold, srv_read_ahead_threshold,
PLUGIN_VAR_RQCMDARG,
"Number of pages that must be accessed sequentially for InnoDB to "
@ -11091,6 +11098,7 @@ static struct st_mysql_sys_var* innobase_system_variables[]= {
#if defined UNIV_DEBUG || defined UNIV_IBUF_DEBUG
MYSQL_SYSVAR(change_buffering_debug),
#endif /* UNIV_DEBUG || UNIV_IBUF_DEBUG */
MYSQL_SYSVAR(random_read_ahead),
MYSQL_SYSVAR(read_ahead_threshold),
MYSQL_SYSVAR(io_capacity),
NULL

14
storage/innodb_plugin/include/buf0buf.h
View File

@ -427,6 +427,18 @@ buf_block_get_freed_page_clock(
__attribute__((pure));
/********************************************************************//**
Tells if a block is still close enough to the MRU end of the LRU list
meaning that it is not in danger of getting evicted and also implying
that it has been accessed recently.
Note that this is for heuristics only and does not reserve buffer pool
mutex.
@return TRUE if block is close to MRU end of LRU */
UNIV_INLINE
ibool
buf_page_peek_if_young(
/*===================*/
const buf_page_t* bpage); /*!< in: block */
/********************************************************************//**
Recommends a move of a block to the start of the LRU list if there is danger
of dropping from the buffer pool. NOTE: does not reserve the buffer pool
mutex.
@ -1334,6 +1346,8 @@ struct buf_pool_stat_struct{
ulint n_pages_written;/*!< number write operations */
ulint n_pages_created;/*!< number of pages created
in the pool with no read */
ulint n_ra_pages_read_rnd;/*!< number of pages read in
as part of random read ahead */
ulint n_ra_pages_read;/*!< number of pages read in
as part of read ahead */
ulint n_ra_pages_evicted;/*!< number of read ahead

28
storage/innodb_plugin/include/buf0buf.ic
View File

@ -61,6 +61,27 @@ buf_block_get_freed_page_clock(
return(buf_page_get_freed_page_clock(&block->page));
}
/********************************************************************//**
Tells if a block is still close enough to the MRU end of the LRU list
meaning that it is not in danger of getting evicted and also implying
that it has been accessed recently.
Note that this is for heuristics only and does not reserve buffer pool
mutex.
@return TRUE if block is close to MRU end of LRU */
UNIV_INLINE
ibool
buf_page_peek_if_young(
/*===================*/
const buf_page_t* bpage) /*!< in: block */
{
/* FIXME: bpage->freed_page_clock is 31 bits */
return((buf_pool->freed_page_clock & ((1UL << 31) - 1))
< ((ulint) bpage->freed_page_clock
+ (buf_pool->curr_size
* (BUF_LRU_OLD_RATIO_DIV - buf_LRU_old_ratio)
/ (BUF_LRU_OLD_RATIO_DIV * 4))));
}
/********************************************************************//**
Recommends a move of a block to the start of the LRU list if there is danger
of dropping from the buffer pool. NOTE: does not reserve the buffer pool
@ -89,12 +110,7 @@ buf_page_peek_if_too_old(
buf_pool->stat.n_pages_not_made_young++;
return(FALSE);
} else {
/* FIXME: bpage->freed_page_clock is 31 bits */
return((buf_pool->freed_page_clock & ((1UL << 31) - 1))
> ((ulint) bpage->freed_page_clock
+ (buf_pool->curr_size
* (BUF_LRU_OLD_RATIO_DIV - buf_LRU_old_ratio)
/ (BUF_LRU_OLD_RATIO_DIV * 4))));
return(!buf_page_peek_if_young(bpage));
}
}

2
storage/innodb_plugin/include/srv0srv.h
View File

@ -143,6 +143,7 @@ extern ulint srv_mem_pool_size;
extern ulint srv_lock_table_size;
extern ulint srv_n_file_io_threads;
extern my_bool srv_random_read_ahead;
extern ulong srv_read_ahead_threshold;
extern ulint srv_n_read_io_threads;
extern ulint srv_n_write_io_threads;
@ -618,6 +619,7 @@ struct export_var_struct{
ulint innodb_buffer_pool_wait_free; /*!< srv_buf_pool_wait_free */
ulint innodb_buffer_pool_pages_flushed; /*!< srv_buf_pool_flushed */
ulint innodb_buffer_pool_write_requests;/*!< srv_buf_pool_write_requests */
ulint innodb_buffer_pool_read_ahead_rnd;/*!< srv_read_ahead_rnd */
ulint innodb_buffer_pool_read_ahead; /*!< srv_read_ahead */
ulint innodb_buffer_pool_read_ahead_evicted;/*!< srv_read_ahead evicted*/
ulint innodb_dblwr_pages_written; /*!< srv_dblwr_pages_written */

4
storage/innodb_plugin/srv/srv0srv.c
View File

@ -203,6 +203,8 @@ UNIV_INTERN ulint srv_n_file_io_threads = ULINT_MAX;
UNIV_INTERN ulint srv_n_read_io_threads = ULINT_MAX;
UNIV_INTERN ulint srv_n_write_io_threads = ULINT_MAX;
/* Switch to enable random read ahead. */
UNIV_INTERN my_bool srv_random_read_ahead = FALSE;
/* User settable value of the number of pages that must be present
in the buffer cache and accessed sequentially for InnoDB to trigger a
readahead request. */
@ -1906,6 +1908,8 @@ srv_export_innodb_status(void)
export_vars.innodb_buffer_pool_wait_free = srv_buf_pool_wait_free;
export_vars.innodb_buffer_pool_pages_flushed = srv_buf_pool_flushed;
export_vars.innodb_buffer_pool_reads = srv_buf_pool_reads;
export_vars.innodb_buffer_pool_read_ahead_rnd
= buf_pool->stat.n_ra_pages_read_rnd;
export_vars.innodb_buffer_pool_read_ahead
= buf_pool->stat.n_ra_pages_read;
export_vars.innodb_buffer_pool_read_ahead_evicted