Backport innodb_max_purge_lag from 4.1

innobase/include/srv0srv.h:
  Add configuration parameter srv_max_purge_lag.
  Add global variable srv_dml_needed_delay.
innobase/include/trx0sys.h:
  Add trx_sys->rseg_history_len
innobase/row/row0mysql.c:
  Add row_mysql_delay_if_needed() for delaying INSERTs, UPDATEs and
  DELETEs for srv_dml_needed_delay microseconds.
innobase/srv/srv0srv.c:
  Define global variable srv_dml_needed_delay.
  Define configuration parameter srv_max_purge_lag.
innobase/trx/trx0purge.c:
  Update trx_sys->rseg_history_len.
  trx_purge(): Compute srv_dml_needed_delay from srv_max_purge_lag
  and trx_sys->rseg_history_len.
innobase/trx/trx0rseg.c:
  Initialize trx_sys->rseg_history_len at InnoDB start-up.
sql/ha_innodb.h:
  Add configuration parameter srv_max_purge_lag.
sql/mysqld.cc:
  Add startup option innodb_max_purge_lag,
  with default value 0 (meaning infinite, disabling the feature).
sql/set_var.cc:
  Add global variable innodb_max_purge_lag.

2 files changed, 44 insertions, 1 deletions

diff --git a/innobase/trx/trx0purge.c b/innobase/trx/trx0purge.c
index a8b6b9fcc21..d772af47b29 100644
--- a/innobase/trx/trx0purge.c
+++ b/innobase/trx/trx0purge.c
@@ -295,6 +295,9 @@ trx_purge_add_update_undo_to_history(
 	/* Add the log as the first in the history list */
 	flst_add_first(rseg_header + TRX_RSEG_HISTORY,
 				undo_header + TRX_UNDO_HISTORY_NODE, mtr);
+	mutex_enter(&kernel_mutex);
+	trx_sys->rseg_history_len++;
+	mutex_exit(&kernel_mutex);
 
 	/* Write the trx number to the undo log header */
 	mlog_write_dulint(undo_header + TRX_UNDO_TRX_NO, trx->no, mtr);
@@ -386,6 +389,12 @@ loop:
 
 	flst_cut_end(rseg_hdr + TRX_RSEG_HISTORY,
 			log_hdr + TRX_UNDO_HISTORY_NODE, n_removed_logs, &mtr);
+
+	mutex_enter(&kernel_mutex);
+	ut_ad(trx_sys->rseg_history_len >= n_removed_logs);
+	trx_sys->rseg_history_len -= n_removed_logs;
+	mutex_exit(&kernel_mutex);
+
 	freed = FALSE;
 
 	while (!freed) {
@@ -470,6 +479,11 @@ loop:
 	}
 
 	if (cmp >= 0) {
+		mutex_enter(&kernel_mutex);
+		ut_a(trx_sys->rseg_history_len >= n_removed_logs);
+		trx_sys->rseg_history_len -= n_removed_logs;
+		mutex_exit(&kernel_mutex);
+
 		flst_truncate_end(rseg_hdr + TRX_RSEG_HISTORY,
 	    			log_hdr + TRX_UNDO_HISTORY_NODE,
 				n_removed_logs, &mtr);
@@ -1031,6 +1045,30 @@ trx_purge(void)
 	purge_sys->view = NULL;
 	mem_heap_empty(purge_sys->heap);
 
+	/* Determine how much data manipulation language (DML) statements
+	need to be delayed in order to reduce the lagging of the purge
+	thread. */
+	srv_dml_needed_delay = 0; /* in microseconds; default: no delay */
+
+	/* If we cannot advance the 'purge view' because of an old
+	'consistent read view', then the DML statements cannot be delayed.
+	Also, srv_max_purge_lag <= 0 means 'infinity'. */
+	if (srv_max_purge_lag > 0
+			&& !UT_LIST_GET_LAST(trx_sys->view_list)) {
+		float	ratio = (float) trx_sys->rseg_history_len
+				/ srv_max_purge_lag;
+		if (ratio > ULINT_MAX / 10000) {
+			/* Avoid overflow: maximum delay is 4295 seconds */
+			srv_dml_needed_delay = ULINT_MAX;
+		} else if (ratio > 1) {
+			/* If the history list length exceeds the
+			innodb_max_purge_lag, the
+			data manipulation statements are delayed
+			by at least 5000 microseconds. */
+			srv_dml_needed_delay = (ulint) ((ratio - .5) * 10000);
+		}
+	}
+
 	purge_sys->view = read_view_oldest_copy_or_open_new(NULL,
 							purge_sys->heap);
 	mutex_exit(&kernel_mutex);	
diff --git a/innobase/trx/trx0rseg.c b/innobase/trx/trx0rseg.c
index e3885c86def..a01d4bb835d 100644
--- a/innobase/trx/trx0rseg.c
+++ b/innobase/trx/trx0rseg.c
@@ -135,6 +135,7 @@ trx_rseg_mem_create(
 	trx_ulogf_t*	undo_log_hdr;
 	fil_addr_t	node_addr;
 	ulint		sum_of_undo_sizes;
+	ulint		len;
 
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(mutex_own(&kernel_mutex));
@@ -166,7 +167,9 @@ trx_rseg_mem_create(
 							MLOG_4BYTES, mtr)
 			  + 1 + sum_of_undo_sizes;
 
-	if (flst_get_len(rseg_header + TRX_RSEG_HISTORY, mtr) > 0) {
+	len = flst_get_len(rseg_header + TRX_RSEG_HISTORY, mtr);
+	if (len > 0) {
+		trx_sys->rseg_history_len += len;
 
 		node_addr = trx_purge_get_log_from_hist(
 			      flst_get_last(rseg_header + TRX_RSEG_HISTORY,
@@ -206,6 +209,8 @@ trx_rseg_list_and_array_init(
 
 	UT_LIST_INIT(trx_sys->rseg_list);
 
+	trx_sys->rseg_history_len = 0;
+
 	for (i = 0; i < TRX_SYS_N_RSEGS; i++) {
 
 		page_no = trx_sysf_rseg_get_page_no(sys_header, i, mtr);