static unsigned long
ll_read_ahead_pages(const struct lu_env *env, struct cl_io *io,
struct cl_page_list *queue, struct ll_readahead_state *ras,
- struct ra_io_arg *ria, pgoff_t *ra_end)
+ struct ra_io_arg *ria, pgoff_t *ra_end, pgoff_t skip_index)
{
struct cl_read_ahead ra = { 0 };
/* busy page count is per stride */
for (page_idx = ria->ria_start_idx;
page_idx <= ria->ria_end_idx && ria->ria_reserved > 0;
page_idx++) {
+ if (skip_index && page_idx == skip_index)
+ continue;
if (ras_inside_ra_window(page_idx, ria)) {
if (ra.cra_end_idx == 0 || ra.cra_end_idx < page_idx) {
pgoff_t end_idx;
if (ras->ras_rpc_pages != ra.cra_rpc_pages &&
ra.cra_rpc_pages > 0)
ras->ras_rpc_pages = ra.cra_rpc_pages;
- /* trim it to align with optimal RPC size */
- end_idx = ras_align(ras, ria->ria_end_idx + 1);
- if (end_idx > 0 && !ria->ria_eof)
- ria->ria_end_idx = end_idx - 1;
+ if (!skip_index) {
+ /* trim it to align with optimal RPC size */
+ end_idx = ras_align(ras, ria->ria_end_idx + 1);
+ if (end_idx > 0 && !ria->ria_eof)
+ ria->ria_end_idx = end_idx - 1;
+ }
if (ria->ria_end_idx < ria->ria_end_idx_min)
ria->ria_end_idx = ria->ria_end_idx_min;
}
cl_2queue_init(queue);
rc = ll_read_ahead_pages(env, io, &queue->c2_qin, ras, ria,
- &ra_end_idx);
+ &ra_end_idx, 0);
if (ria->ria_reserved != 0)
ll_ra_count_put(ll_i2sbi(inode), ria->ria_reserved);
if (queue->c2_qin.pl_nr > 0) {
static int ll_readahead(const struct lu_env *env, struct cl_io *io,
struct cl_page_list *queue,
struct ll_readahead_state *ras, bool hit,
- struct file *file)
+ struct file *file, pgoff_t skip_index)
{
struct vvp_io *vio = vvp_env_io(env);
struct ll_thread_info *lti = ll_env_info(env);
if (ras->ras_window_pages > 0)
end_idx = ras->ras_window_start_idx + ras->ras_window_pages - 1;
+ if (skip_index)
+ end_idx = start_idx + ras->ras_window_pages - 1;
+
/* Enlarge the RA window to encompass the full read */
if (vio->vui_ra_valid &&
end_idx < vio->vui_ra_start_idx + vio->vui_ra_pages - 1)
ria->ria_start_idx;
}
+ /* don't over reserved for mmap range read */
+ if (skip_index)
+ pages_min = 0;
+
ria->ria_reserved = ll_ra_count_get(ll_i2sbi(inode), ria, pages,
pages_min);
if (ria->ria_reserved < pages)
atomic_read(&ll_i2sbi(inode)->ll_ra_info.ra_cur_pages),
ll_i2sbi(inode)->ll_ra_info.ra_max_pages);
- ret = ll_read_ahead_pages(env, io, queue, ras, ria, &ra_end_idx);
-
+ ret = ll_read_ahead_pages(env, io, queue, ras, ria, &ra_end_idx,
+ skip_index);
if (ria->ria_reserved != 0)
ll_ra_count_put(ll_i2sbi(inode), ria->ria_reserved);
ras_reset(ras, 0);
ras->ras_last_read_end_bytes = 0;
ras->ras_requests = 0;
+ ras->ras_range_min_start_idx = 0;
+ ras->ras_range_max_end_idx = 0;
+ ras->ras_range_requests = 0;
+ ras->ras_last_range_pages = 0;
}
/*
8UL << PAGE_SHIFT, 8UL << PAGE_SHIFT);
}
+static inline bool is_loose_mmap_read(struct ll_sb_info *sbi,
+ struct ll_readahead_state *ras,
+ unsigned long pos)
+{
+ unsigned long range_pages = sbi->ll_ra_info.ra_range_pages;
+
+ return pos_in_window(pos, ras->ras_last_read_end_bytes,
+ range_pages << PAGE_SHIFT,
+ range_pages << PAGE_SHIFT);
+}
+
+/**
+ * We have observed slow mmap read performances for some
+ * applications. The problem is if access pattern is neither
+ * sequential nor stride, but could be still adjacent in a
+ * small range and then seek a random position.
+ *
+ * So the pattern could be something like this:
+ *
+ * [1M data] [hole] [0.5M data] [hole] [0.7M data] [1M data]
+ *
+ *
+ * Every time an application reads mmap data, it may not only
+ * read a single 4KB page, but aslo a cluster of nearby pages in
+ * a range(e.g. 1MB) of the first page after a cache miss.
+ *
+ * The readahead engine is modified to track the range size of
+ * a cluster of mmap reads, so that after a seek and/or cache miss,
+ * the range size is used to efficiently prefetch multiple pages
+ * in a single RPC rather than many small RPCs.
+ */
+static void ras_detect_cluster_range(struct ll_readahead_state *ras,
+ struct ll_sb_info *sbi,
+ unsigned long pos, unsigned long count)
+{
+ pgoff_t last_pages, pages;
+ pgoff_t end_idx = (pos + count - 1) >> PAGE_SHIFT;
+
+ last_pages = ras->ras_range_max_end_idx -
+ ras->ras_range_min_start_idx + 1;
+ /* First time come here */
+ if (!ras->ras_range_max_end_idx)
+ goto out;
+
+ /* Random or Stride read */
+ if (!is_loose_mmap_read(sbi, ras, pos))
+ goto out;
+
+ ras->ras_range_requests++;
+ if (ras->ras_range_max_end_idx < end_idx)
+ ras->ras_range_max_end_idx = end_idx;
+
+ if (ras->ras_range_min_start_idx > (pos >> PAGE_SHIFT))
+ ras->ras_range_min_start_idx = pos >> PAGE_SHIFT;
+
+ /* Out of range, consider it as random or stride */
+ pages = ras->ras_range_max_end_idx -
+ ras->ras_range_min_start_idx + 1;
+ if (pages <= sbi->ll_ra_info.ra_range_pages)
+ return;
+out:
+ ras->ras_last_range_pages = last_pages;
+ ras->ras_range_requests = 0;
+ ras->ras_range_min_start_idx = pos >> PAGE_SHIFT;
+ ras->ras_range_max_end_idx = end_idx;
+}
+
static void ras_detect_read_pattern(struct ll_readahead_state *ras,
struct ll_sb_info *sbi,
loff_t pos, size_t count, bool mmap)
ras->ras_consecutive_bytes += count;
if (mmap) {
pgoff_t idx = ras->ras_consecutive_bytes >> PAGE_SHIFT;
+ unsigned long ra_range_pages =
+ max_t(unsigned long, RA_MIN_MMAP_RANGE_PAGES,
+ sbi->ll_ra_info.ra_range_pages);
- if ((idx >= 4 && (idx & 3UL) == 0) || stride_detect)
+ if ((idx >= ra_range_pages &&
+ idx % ra_range_pages == 0) || stride_detect)
ras->ras_need_increase_window = true;
} else if ((ras->ras_consecutive_requests > 1 || stride_detect)) {
ras->ras_need_increase_window = true;
if (ras->ras_no_miss_check)
GOTO(out_unlock, 0);
- if (flags & LL_RAS_MMAP)
+ if (flags & LL_RAS_MMAP) {
+ unsigned long ra_pages;
+
+ ras_detect_cluster_range(ras, sbi, index << PAGE_SHIFT,
+ PAGE_SIZE);
ras_detect_read_pattern(ras, sbi, (loff_t)index << PAGE_SHIFT,
PAGE_SIZE, true);
+ /* we did not detect anything but we could prefetch */
+ if (!ras->ras_need_increase_window &&
+ ras->ras_window_pages <= sbi->ll_ra_info.ra_range_pages &&
+ ras->ras_range_requests >= 2) {
+ if (!hit) {
+ ra_pages = max_t(unsigned long,
+ RA_MIN_MMAP_RANGE_PAGES,
+ ras->ras_last_range_pages);
+ if (index < ra_pages / 2)
+ index = 0;
+ else
+ index -= ra_pages / 2;
+ ras->ras_window_pages = ra_pages;
+ ll_ra_stats_inc_sbi(sbi,
+ RA_STAT_MMAP_RANGE_READ);
+ } else {
+ ras->ras_window_pages = 0;
+ }
+ goto skip;
+ }
+ }
+
if (!hit && ras->ras_window_pages &&
index < ras->ras_next_readahead_idx &&
pos_in_window(index, ras->ras_window_start_idx, 0,
GOTO(out_unlock, 0);
}
}
+
+skip:
ras_set_start(ras, index);
if (stride_io_mode(ras)) {
io_end_index = cl_index(io->ci_obj, io->u.ci_rw.crw_pos +
io->u.ci_rw.crw_count - 1);
if (ll_readahead_enabled(sbi) && ras) {
+ pgoff_t skip_index = 0;
+
+ if (ras->ras_next_readahead_idx < vvp_index(vpg))
+ skip_index = vvp_index(vpg);
rc2 = ll_readahead(env, io, &queue->c2_qin, ras,
- uptodate, file);
+ uptodate, file, skip_index);
CDEBUG(D_READA, DFID " %d pages read ahead at %lu\n",
PFID(ll_inode2fid(inode)), rc2, vvp_index(vpg));
} else if (vvp_index(vpg) == io_start_index &&
git://git.whamcloud.com / fs / lustre-release.git / blobdiff