From 5dc37c619b4a250dfd12f8ff4d58a72e07f0ec3c Mon Sep 17 00:00:00 2001
From: wangdi <wangdi>
Date: Thu, 30 Oct 2008 21:46:32 +0000
Subject: [PATCH] Branch: HEAD Once the unmatched stride IO mode is detected,
shrink the stride-ahead window to 0. if it does hit cache miss, and
read-pattern is still stride-io mode, does not reset the stride window, but
also does not increase the stride window length in this case. b=17197
i=Nikita i=Andreas
---
lustre/ChangeLog | 8 +++
lustre/llite/rw.c | 121 ++++++++++++++++++++++------------------------
2 files changed, 66 insertions(+), 63 deletions(-)
diff --git a/lustre/ChangeLog b/lustre/ChangeLog
index 9cc3e32919..8cc4fcb23a 100644
--- a/lustre/ChangeLog
+++ b/lustre/ChangeLog
@@ -1743,6 +1743,14 @@ Details : Checks validity of on-disk block bitmap. Also it does better
checking of number of applied preallocations. When corruption is
found, it turns filesystem readonly to prevent further corruptions.
+Severity : normal
+Bugzilla : 17197
+Description: (rw.c:1323:ll_read_ahead_pages()) ASSERTION(page_idx > ria->ria_stoff) failed
+Details : Once the unmatched stride IO mode is detected, shrink the stride-ahead
+ window to 0. If it does hit cache miss, and read-pattern is still
+ stride-io mode, does not reset the stride window, but also does not
+ increase the stride window length in this case.
+
--------------------------------------------------------------------------------
2007-08-10 Cluster File Systems, Inc. <info@clusterfs.com>
diff --git a/lustre/llite/rw.c b/lustre/llite/rw.c
index f6813408a9..6a2be0ad01 100644
--- a/lustre/llite/rw.c
+++ b/lustre/llite/rw.c
@@ -1697,6 +1697,8 @@ static void ras_reset(struct ll_readahead_state *ras, unsigned long index)
static void ras_stride_reset(struct ll_readahead_state *ras)
{
ras->ras_consecutive_stride_requests = 0;
+ ras->ras_stride_length = 0;
+ ras->ras_stride_pages = 0;
RAS_CDEBUG(ras);
}
@@ -1708,46 +1710,39 @@ void ll_readahead_init(struct inode *inode, struct ll_readahead_state *ras)
INIT_LIST_HEAD(&ras->ras_read_beads);
}
-/* Check whether the read request is in the stride window.
+/*
+ * Check whether the read request is in the stride window.
* If it is in the stride window, return 1, otherwise return 0.
- * and also update stride_gap and stride_pages.
*/
static int index_in_stride_window(unsigned long index,
struct ll_readahead_state *ras,
struct inode *inode)
{
- int stride_gap = index - ras->ras_last_readpage - 1;
+ unsigned long stride_gap = index - ras->ras_last_readpage - 1;
+
+ if (ras->ras_stride_length == 0 || ras->ras_stride_pages == 0)
+ return 0;
- LASSERT(stride_gap != 0);
+ /* If it is contiguous read */
+ if (stride_gap == 0)
+ return ras->ras_consecutive_pages + 1 <= ras->ras_stride_pages;
- if (ras->ras_consecutive_pages == 0)
- return 0;
+ /* Otherwise check the stride by itself */
+ return (ras->ras_stride_length - ras->ras_stride_pages) == stride_gap &&
+ ras->ras_consecutive_pages == ras->ras_stride_pages;
+}
- /*Otherwise check the stride by itself */
- if ((ras->ras_stride_length - ras->ras_stride_pages) == stride_gap &&
- ras->ras_consecutive_pages == ras->ras_stride_pages)
- return 1;
+static void ras_update_stride_detector(struct ll_readahead_state *ras,
+ unsigned long index)
+{
+ unsigned long stride_gap = index - ras->ras_last_readpage - 1;
- if (stride_gap >= 0) {
- /*
- * only set stride_pages, stride_length if
- * it is forward reading ( stride_gap > 0)
- */
+ if (!stride_io_mode(ras) && (stride_gap != 0 ||
+ ras->ras_consecutive_stride_requests == 0)) {
ras->ras_stride_pages = ras->ras_consecutive_pages;
- ras->ras_stride_length = stride_gap + ras->ras_consecutive_pages;
- } else {
- /*
- * If stride_gap < 0,(back_forward reading),
- * reset the stride_pages/length.
- * FIXME:back_ward stride I/O read.
- *
- */
- ras->ras_stride_pages = 0;
- ras->ras_stride_length = 0;
+ ras->ras_stride_length = stride_gap +ras->ras_consecutive_pages;
}
RAS_CDEBUG(ras);
-
- return 0;
}
static unsigned long
@@ -1819,7 +1814,7 @@ static void ras_update(struct ll_sb_info *sbi, struct inode *inode,
unsigned hit)
{
struct ll_ra_info *ra = &sbi->ll_ra_info;
- int zero = 0, stride_zero = 0, stride_detect = 0, ra_miss = 0;
+ int zero = 0, stride_detect = 0, ra_miss = 0;
ENTRY;
spin_lock(&ras->ras_lock);
@@ -1834,20 +1829,11 @@ static void ras_update(struct ll_sb_info *sbi, struct inode *inode,
if (!index_in_window(index, ras->ras_last_readpage, 8, 8)) {
zero = 1;
ll_ra_stats_inc_sbi(sbi, RA_STAT_DISTANT_READPAGE);
- /* check whether it is in stride I/O mode*/
- if (!index_in_stride_window(index, ras, inode))
- stride_zero = 1;
} else if (!hit && ras->ras_window_len &&
index < ras->ras_next_readahead &&
index_in_window(index, ras->ras_window_start, 0,
ras->ras_window_len)) {
- zero = 1;
ra_miss = 1;
- /* If it hits read-ahead miss and the stride I/O is still
- * not detected, reset stride stuff to re-detect the whole
- * stride I/O mode to avoid complication */
- if (!stride_io_mode(ras))
- stride_zero = 1;
ll_ra_stats_inc_sbi(sbi, RA_STAT_MISS_IN_WINDOW);
}
@@ -1876,42 +1862,51 @@ static void ras_update(struct ll_sb_info *sbi, struct inode *inode,
GOTO(out_unlock, 0);
}
}
-
if (zero) {
- /* If it is discontinuous read, check
- * whether it is stride I/O mode*/
- if (stride_zero) {
+ /* check whether it is in stride I/O mode*/
+ if (!index_in_stride_window(index, ras, inode)) {
ras_reset(ras, index);
ras->ras_consecutive_pages++;
ras_stride_reset(ras);
- RAS_CDEBUG(ras);
GOTO(out_unlock, 0);
} else {
- /* The read is still in stride window or
- * it hits read-ahead miss */
-
- /* If ra-window miss is hitted, which probably means VM
- * pressure, and some read-ahead pages were reclaimed.So
- * the length of ra-window will not increased, but also
- * not reset to avoid redetecting the stride I/O mode.*/
- ras->ras_consecutive_requests = 0;
- if (!ra_miss) {
- ras->ras_consecutive_pages = 0;
- if (++ras->ras_consecutive_stride_requests > 1)
- stride_detect = 1;
- }
+ ras->ras_consecutive_requests = 0;
+ if (++ras->ras_consecutive_stride_requests > 1)
+ stride_detect = 1;
RAS_CDEBUG(ras);
}
- } else if (ras->ras_consecutive_stride_requests > 1) {
- /* If this is contiguous read but in stride I/O mode
- * currently, check whether stride step still is valid,
- * if invalid, it will reset the stride ra window*/
- if (ras->ras_consecutive_pages + 1 > ras->ras_stride_pages)
- ras_stride_reset(ras);
+ } else {
+ if (ra_miss) {
+ if (index_in_stride_window(index, ras, inode) &&
+ stride_io_mode(ras)) {
+ /*If stride-RA hit cache miss, the stride dector
+ *will not be reset to avoid the overhead of
+ *redetecting read-ahead mode */
+ if (index != ras->ras_last_readpage + 1)
+ ras->ras_consecutive_pages = 0;
+ RAS_CDEBUG(ras);
+ } else {
+ /* Reset both stride window and normal RA window */
+ ras_reset(ras, index);
+ ras->ras_consecutive_pages++;
+ ras_stride_reset(ras);
+ GOTO(out_unlock, 0);
+ }
+ } else if (stride_io_mode(ras)) {
+ /* If this is contiguous read but in stride I/O mode
+ * currently, check whether stride step still is valid,
+ * if invalid, it will reset the stride ra window*/
+ if (!index_in_stride_window(index, ras, inode)) {
+ /* Shrink stride read-ahead window to be zero */
+ ras_stride_reset(ras);
+ ras->ras_window_len = 0;
+ ras->ras_next_readahead = index;
+ }
+ }
}
-
- ras->ras_last_readpage = index;
ras->ras_consecutive_pages++;
+ ras_update_stride_detector(ras, index);
+ ras->ras_last_readpage = index;
ras_set_start(ras, index);
ras->ras_next_readahead = max(ras->ras_window_start,
ras->ras_next_readahead);
--
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