#define RAS_CDEBUG(ras) \
CDEBUG(D_READA, \
- "lrp %lu cr %lu cp %lu ws %lu wl %lu nra %lu r %lu ri %lu\n", \
+ "lrp %lu cr %lu cp %lu ws %lu wl %lu nra %lu r %lu ri %lu" \
+ "csr %lu sf %lu sp %lu sl %lu \n", \
ras->ras_last_readpage, ras->ras_consecutive_requests, \
ras->ras_consecutive_pages, ras->ras_window_start, \
ras->ras_window_len, ras->ras_next_readahead, \
- ras->ras_requests, ras->ras_request_index);
+ ras->ras_requests, ras->ras_request_index, \
+ ras->ras_consecutive_stride_requests, ras->ras_stride_offset, \
+ ras->ras_stride_pages, ras->ras_stride_length)
static int index_in_window(unsigned long index, unsigned long point,
unsigned long before, unsigned long after)
return bead;
}
+static int ll_read_ahead_page(struct obd_export *exp, struct obd_io_group *oig,
+ int index, struct address_space *mapping)
+{
+ struct ll_async_page *llap;
+ struct page *page;
+ unsigned int gfp_mask = 0;
+ int rc = 0;
+
+ gfp_mask = GFP_HIGHUSER & ~__GFP_WAIT;
+#ifdef __GFP_NOWARN
+ gfp_mask |= __GFP_NOWARN;
+#endif
+ page = grab_cache_page_nowait_gfp(mapping, index, gfp_mask);
+ if (page == NULL) {
+ ll_ra_stats_inc(mapping, RA_STAT_FAILED_GRAB_PAGE);
+ CDEBUG(D_READA, "g_c_p_n failed\n");
+ return 0;
+ }
+
+ /* Check if page was truncated or reclaimed */
+ if (page->mapping != mapping) {
+ ll_ra_stats_inc(mapping, RA_STAT_WRONG_GRAB_PAGE);
+ CDEBUG(D_READA, "g_c_p_n returned invalid page\n");
+ GOTO(unlock_page, rc = 0);
+ }
+
+ /* we do this first so that we can see the page in the /proc
+ * accounting */
+ llap = llap_from_page(page, LLAP_ORIGIN_READAHEAD);
+ if (IS_ERR(llap) || llap->llap_defer_uptodate) {
+ if (PTR_ERR(llap) == -ENOLCK) {
+ ll_ra_stats_inc(mapping, RA_STAT_FAILED_MATCH);
+ CDEBUG(D_READA | D_PAGE,
+ "Adding page to cache failed index "
+ "%d\n", index);
+ CDEBUG(D_READA, "nolock page\n");
+ GOTO(unlock_page, rc = -ENOLCK);
+ }
+ CDEBUG(D_READA, "read-ahead page\n");
+ GOTO(unlock_page, rc = 0);
+ }
+
+ /* skip completed pages */
+ if (Page_Uptodate(page))
+ GOTO(unlock_page, rc = 0);
+
+ /* bail out when we hit the end of the lock. */
+ rc = ll_issue_page_read(exp, llap, oig, 1);
+ if (rc == 0) {
+ LL_CDEBUG_PAGE(D_READA | D_PAGE, page, "started read-ahead\n");
+ rc = 1;
+ } else {
+unlock_page:
+ unlock_page(page);
+ LL_CDEBUG_PAGE(D_READA | D_PAGE, page, "skipping read-ahead\n");
+ }
+ page_cache_release(page);
+ return rc;
+}
+
+/* ra_io_arg will be filled in the beginning of ll_readahead with
+ * ras_lock, then the following ll_read_ahead_pages will read RA
+ * pages according to this arg, all the items in this structure are
+ * counted by page index.
+ */
+struct ra_io_arg {
+ unsigned long ria_start; /* start offset of read-ahead*/
+ unsigned long ria_end; /* end offset of read-ahead*/
+ /* If stride read pattern is detected, ria_stoff means where
+ * stride read is started. Note: for normal read-ahead, the
+ * value here is meaningless, and also it will not be accessed*/
+ pgoff_t ria_stoff;
+ /* ria_length and ria_pages are the length and pages length in the
+ * stride I/O mode. And they will also be used to check whether
+ * it is stride I/O read-ahead in the read-ahead pages*/
+ unsigned long ria_length;
+ unsigned long ria_pages;
+};
+
+#define RIA_DEBUG(ria) \
+ CDEBUG(D_READA, "rs %lu re %lu ro %lu rl %lu rp %lu\n", \
+ ria->ria_start, ria->ria_end, ria->ria_stoff, ria->ria_length,\
+ ria->ria_pages)
+
+#define RAS_INCREASE_STEP (1024 * 1024 >> CFS_PAGE_SHIFT)
+
+static inline int stride_io_mode(struct ll_readahead_state *ras)
+{
+ return ras->ras_consecutive_stride_requests > 1;
+}
+
+/* The function calculates how much pages will be read in
+ * [off, off + length], which will be read by stride I/O mode,
+ * stride_offset = st_off, stride_lengh = st_len,
+ * stride_pages = st_pgs
+ */
+static unsigned long
+stride_pg_count(pgoff_t st_off, unsigned long st_len, unsigned long st_pgs,
+ unsigned long off, unsigned length)
+{
+ unsigned long cont_len = st_off > off ? st_off - off : 0;
+ unsigned long stride_len = length + off > st_off ?
+ length + off + 1 - st_off : 0;
+ unsigned long left, pg_count;
+
+ if (st_len == 0 || length == 0)
+ return length;
+
+ left = do_div(stride_len, st_len);
+ left = min(left, st_pgs);
+
+ pg_count = left + stride_len * st_pgs + cont_len;
+
+ LASSERT(pg_count >= left);
+
+ CDEBUG(D_READA, "st_off %lu, st_len %lu st_pgs %lu off %lu length %u"
+ "pgcount %lu\n", st_off, st_len, st_pgs, off, length, pg_count);
+
+ return pg_count;
+}
+
+static int ria_page_count(struct ra_io_arg *ria)
+{
+ __u64 length = ria->ria_end >= ria->ria_start ?
+ ria->ria_end - ria->ria_start + 1 : 0;
+
+ return stride_pg_count(ria->ria_stoff, ria->ria_length,
+ ria->ria_pages, ria->ria_start,
+ length);
+}
+
+/*Check whether the index is in the defined ra-window */
+static int ras_inside_ra_window(unsigned long idx, struct ra_io_arg *ria)
+{
+ /* If ria_length == ria_pages, it means non-stride I/O mode,
+ * idx should always inside read-ahead window in this case
+ * For stride I/O mode, just check whether the idx is inside
+ * the ria_pages. */
+ return ria->ria_length == 0 || ria->ria_length == ria->ria_pages ||
+ (idx - ria->ria_stoff) % ria->ria_length < ria->ria_pages;
+}
+
+static int ll_read_ahead_pages(struct obd_export *exp,
+ struct obd_io_group *oig,
+ struct ra_io_arg *ria,
+ unsigned long *reserved_pages,
+ struct address_space *mapping,
+ unsigned long *ra_end)
+{
+ int rc, count = 0, stride_ria;
+ unsigned long page_idx;
+
+ LASSERT(ria != NULL);
+ RIA_DEBUG(ria);
+
+ stride_ria = ria->ria_length > ria->ria_pages && ria->ria_pages > 0;
+ for (page_idx = ria->ria_start; page_idx <= ria->ria_end &&
+ *reserved_pages > 0; page_idx++) {
+ if (ras_inside_ra_window(page_idx, ria)) {
+ /* If the page is inside the read-ahead window*/
+ rc = ll_read_ahead_page(exp, oig, page_idx, mapping);
+ if (rc == 1) {
+ (*reserved_pages)--;
+ count ++;
+ } else if (rc == -ENOLCK)
+ break;
+ } else if (stride_ria) {
+ /* If it is not in the read-ahead window, and it is
+ * read-ahead mode, then check whether it should skip
+ * the stride gap */
+ pgoff_t offset;
+ /* FIXME: This assertion only is valid when it is for
+ * forward read-ahead, it will be fixed when backward
+ * read-ahead is implemented */
+ LASSERTF(page_idx > ria->ria_stoff, "since %lu in the"
+ " gap of ra window,it should bigger than stride"
+ " offset %lu \n", page_idx, ria->ria_stoff);
+
+ offset = page_idx - ria->ria_stoff;
+ offset = offset % (ria->ria_length);
+ if (offset > ria->ria_pages) {
+ page_idx += ria->ria_length - offset;
+ CDEBUG(D_READA, "i %lu skip %lu \n", page_idx,
+ ria->ria_length - offset);
+ continue;
+ }
+ }
+ }
+ *ra_end = page_idx;
+ return count;
+}
+
static int ll_readahead(struct ll_readahead_state *ras,
struct obd_export *exp, struct address_space *mapping,
struct obd_io_group *oig, int flags)
{
- unsigned long i, start = 0, end = 0, reserved;
- struct ll_async_page *llap;
- struct page *page;
- int rc, ret = 0, match_failed = 0;
- __u64 kms;
- unsigned int gfp_mask;
+ unsigned long start = 0, end = 0, reserved;
+ unsigned long ra_end, len;
struct inode *inode;
struct lov_stripe_md *lsm;
struct ll_ra_read *bead;
struct ost_lvb lvb;
+ struct ra_io_arg ria = { 0 };
+ int ret = 0;
+ __u64 kms;
ENTRY;
inode = mapping->host;
ras->ras_window_len = bead->lrr_start + bead->lrr_count -
ras->ras_window_start;
}
- /* Reserve a part of the read-ahead window that we'll be issuing */
+ /* Reserve a part of the read-ahead window that we'll be issuing */
if (ras->ras_window_len) {
start = ras->ras_next_readahead;
end = ras->ras_window_start + ras->ras_window_len - 1;
ras->ras_next_readahead = max(end, end + 1);
RAS_CDEBUG(ras);
}
+ ria.ria_start = start;
+ ria.ria_end = end;
+ /* If stride I/O mode is detected, get stride window*/
+ if (stride_io_mode(ras)) {
+ ria.ria_length = ras->ras_stride_length;
+ ria.ria_pages = ras->ras_stride_pages;
+ }
spin_unlock(&ras->ras_lock);
if (end == 0) {
RETURN(0);
}
- reserved = ll_ra_count_get(ll_i2sbi(inode), end - start + 1);
+ len = ria_page_count(&ria);
+ if (len == 0)
+ RETURN(0);
+
+ reserved = ll_ra_count_get(ll_i2sbi(inode), len);
if (reserved < end - start + 1)
ll_ra_stats_inc(mapping, RA_STAT_MAX_IN_FLIGHT);
- gfp_mask = GFP_HIGHUSER & ~__GFP_WAIT;
-#ifdef __GFP_NOWARN
- gfp_mask |= __GFP_NOWARN;
-#endif
-
- for (i = start; reserved > 0 && !match_failed && i <= end; i++) {
- /* skip locked pages from previous readpage calls */
- page = grab_cache_page_nowait_gfp(mapping, i, gfp_mask);
- if (page == NULL) {
- ll_ra_stats_inc(mapping, RA_STAT_FAILED_GRAB_PAGE);
- CDEBUG(D_READA, "g_c_p_n failed\n");
- continue;
- }
-
- /* Check if page was truncated or reclaimed */
- if (page->mapping != mapping) {
- ll_ra_stats_inc(mapping, RA_STAT_WRONG_GRAB_PAGE);
- CDEBUG(D_READA, "g_c_p_n returned invalid page\n");
- goto next_page;
- }
-
- /* we do this first so that we can see the page in the /proc
- * accounting */
- llap = llap_from_page(page, LLAP_ORIGIN_READAHEAD);
- if (IS_ERR(llap) || llap->llap_defer_uptodate) {
- if (PTR_ERR(llap) == -ENOLCK) {
- ll_ra_stats_inc(mapping, RA_STAT_FAILED_MATCH);
- match_failed = 1;
- CDEBUG(D_READA | D_PAGE,
- "Adding page to cache failed index "
- "%lu\n", i);
- }
- goto next_page;
- }
-
- /* skip completed pages */
- if (Page_Uptodate(page))
- goto next_page;
-
- /* bail when we hit the end of the lock. */
- rc = ll_issue_page_read(exp, llap, oig, 1);
- if (rc == 0) {
- reserved--;
- ret++;
- LL_CDEBUG_PAGE(D_READA| D_PAGE, page,
- "started read-ahead\n");
- } else {
- next_page:
- LL_CDEBUG_PAGE(D_READA | D_PAGE, page,
- "skipping read-ahead\n");
-
- unlock_page(page);
- }
- page_cache_release(page);
- }
+ CDEBUG(D_READA, "reserved page %lu \n", reserved);
+
+ ret = ll_read_ahead_pages(exp, oig, &ria, &reserved, mapping, &ra_end);
LASSERTF(reserved >= 0, "reserved %lu\n", reserved);
if (reserved != 0)
ll_ra_count_put(ll_i2sbi(inode), reserved);
- if (i == end + 1 && end == (kms >> CFS_PAGE_SHIFT))
+
+ if (ra_end == end + 1 && ra_end == (kms >> CFS_PAGE_SHIFT))
ll_ra_stats_inc(mapping, RA_STAT_EOF);
/* if we didn't get to the end of the region we reserved from
* next read-ahead tries from where we left off. we only do so
* if the region we failed to issue read-ahead on is still ahead
* of the app and behind the next index to start read-ahead from */
- if (i != end + 1) {
+ CDEBUG(D_READA, "ra_end %lu end %lu stride end %lu \n",
+ ra_end, end, ria.ria_end);
+
+ if (ra_end != (end + 1)) {
spin_lock(&ras->ras_lock);
- if (i < ras->ras_next_readahead &&
- index_in_window(i, ras->ras_window_start, 0,
- ras->ras_window_len)) {
- ras->ras_next_readahead = i;
- RAS_CDEBUG(ras);
+ if (ra_end < ras->ras_next_readahead &&
+ index_in_window(ra_end, ras->ras_window_start, 0,
+ ras->ras_window_len)) {
+ ras->ras_next_readahead = ra_end;
+ RAS_CDEBUG(ras);
}
spin_unlock(&ras->ras_lock);
}
static void ras_set_start(struct ll_readahead_state *ras, unsigned long index)
{
- ras->ras_window_start = index & (~((1024 * 1024 >> CFS_PAGE_SHIFT) - 1));
+ ras->ras_window_start = index & (~(RAS_INCREASE_STEP - 1));
}
/* called with the ras_lock held or from places where it doesn't matter */
RAS_CDEBUG(ras);
}
+/* called with the ras_lock held or from places where it doesn't matter */
+static void ras_stride_reset(struct ll_readahead_state *ras)
+{
+ ras->ras_consecutive_stride_requests = 0;
+ RAS_CDEBUG(ras);
+}
+
void ll_readahead_init(struct inode *inode, struct ll_readahead_state *ras)
{
spin_lock_init(&ras->ras_lock);
INIT_LIST_HEAD(&ras->ras_read_beads);
}
+/* 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;
+
+ LASSERT(stride_gap != 0);
+
+ if (ras->ras_consecutive_pages == 0)
+ return 0;
+
+ /*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;
+
+ if (stride_gap >= 0) {
+ /*
+ * only set stride_pages, stride_length if
+ * it is forward reading ( stride_gap > 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_CDEBUG(ras);
+
+ return 0;
+}
+
+static unsigned long
+stride_page_count(struct ll_readahead_state *ras, unsigned long len)
+{
+ return stride_pg_count(ras->ras_stride_offset, ras->ras_stride_length,
+ ras->ras_stride_pages, ras->ras_stride_offset,
+ len);
+}
+
+/* Stride Read-ahead window will be increased inc_len according to
+ * stride I/O pattern */
+static void ras_stride_increase_window(struct ll_readahead_state *ras,
+ struct ll_ra_info *ra,
+ unsigned long inc_len)
+{
+ unsigned long left, step, window_len;
+ unsigned long stride_len;
+
+ LASSERT(ras->ras_stride_length > 0);
+
+ stride_len = ras->ras_window_start + ras->ras_window_len -
+ ras->ras_stride_offset;
+
+ LASSERTF(stride_len > 0, "window_start %lu, window_len %lu"
+ "stride_offset %lu\n", ras->ras_window_start,
+ ras->ras_window_len, ras->ras_stride_offset);
+
+ left = stride_len % ras->ras_stride_length;
+
+ window_len = ras->ras_window_len - left;
+
+ if (left < ras->ras_stride_pages)
+ left += inc_len;
+ else
+ left = ras->ras_stride_pages + inc_len;
+
+ LASSERT(ras->ras_stride_pages != 0);
+
+ step = left / ras->ras_stride_pages;
+ left %= ras->ras_stride_pages;
+
+ window_len += step * ras->ras_stride_length + left;
+
+ if (stride_page_count(ras, window_len) <= ra->ra_max_pages)
+ ras->ras_window_len = window_len;
+
+ RAS_CDEBUG(ras);
+}
+
+/* Set stride I/O read-ahead window start offset */
+static void ras_set_stride_offset(struct ll_readahead_state *ras)
+{
+ unsigned long window_len = ras->ras_next_readahead -
+ ras->ras_window_start;
+ unsigned long left;
+
+ LASSERT(ras->ras_stride_length != 0);
+
+ left = window_len % ras->ras_stride_length;
+
+ ras->ras_stride_offset = ras->ras_next_readahead - left;
+
+ RAS_CDEBUG(ras);
+}
+
static void ras_update(struct ll_sb_info *sbi, struct inode *inode,
struct ll_readahead_state *ras, unsigned long index,
unsigned hit)
{
struct ll_ra_info *ra = &sbi->ll_ra_info;
- int zero = 0;
+ int zero = 0, stride_zero = 0, stride_detect = 0, ra_miss = 0;
ENTRY;
spin_lock(&sbi->ll_lock);
if (!index_in_window(index, ras->ras_last_readpage, 8, 8)) {
zero = 1;
ll_ra_stats_inc_unlocked(ra, 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_unlocked(ra, RA_STAT_MISS_IN_WINDOW);
}
}
if (zero) {
- ras_reset(ras, index);
- GOTO(out_unlock, 0);
+ /* If it is discontinuous read, check
+ * whether it is stride I/O mode*/
+ if (stride_zero) {
+ 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_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);
}
ras->ras_last_readpage = index;
ras_set_start(ras, index);
ras->ras_next_readahead = max(ras->ras_window_start,
ras->ras_next_readahead);
+ RAS_CDEBUG(ras);
/* Trigger RA in the mmap case where ras_consecutive_requests
* is not incremented and thus can't be used to trigger RA */
- if (!ras->ras_window_len && ras->ras_consecutive_pages == 3) {
- ras->ras_window_len = 1024 * 1024 >> CFS_PAGE_SHIFT;
+ if (!ras->ras_window_len && ras->ras_consecutive_pages == 4) {
+ ras->ras_window_len = RAS_INCREASE_STEP;
GOTO(out_unlock, 0);
}
+ /* Initially reset the stride window offset to next_readahead*/
+ if (ras->ras_consecutive_stride_requests == 2 && stride_detect)
+ ras_set_stride_offset(ras);
+
/* The initial ras_window_len is set to the request size. To avoid
* uselessly reading and discarding pages for random IO the window is
* only increased once per consecutive request received. */
- if (ras->ras_consecutive_requests > 1 && !ras->ras_request_index) {
- ras->ras_window_len = min(ras->ras_window_len +
- (1024 * 1024 >> CFS_PAGE_SHIFT),
- ra->ra_max_pages);
+ if ((ras->ras_consecutive_requests > 1 &&
+ !ras->ras_request_index) || stride_detect) {
+ if (stride_io_mode(ras))
+ ras_stride_increase_window(ras, ra, RAS_INCREASE_STEP);
+ else
+ ras->ras_window_len = min(ras->ras_window_len +
+ RAS_INCREASE_STEP,
+ ra->ra_max_pages);
}
-
EXIT;
out_unlock:
RAS_CDEBUG(ras);
git://git.whamcloud.com / fs / lustre-release.git / commitdiff