nilfs2: add a tracepoint for tracking stage transition of segment construction
This patch adds a tracepoint for tracking stage transition of block
collection in segment construction. With the tracepoint, we can analysis
the behavior of segment construction in depth. It would be useful for
bottleneck detection and debugging, etc.
The tracepoint is created with the standard trace API of linux (like ext3,
ext4, f2fs and btrfs). So we can analysis with existing tools easily. Of
course, more detailed analysis will be possible if we can create nilfs
specific analysis tools.
Below is an example of event dump with Brendan Gregg's perf-tools
(https://github.com/brendangregg/perf-tools). Time consumption between
each stage can be obtained.
$ sudo bin/tpoint nilfs2:nilfs2_collection_stage_transition
Tracing nilfs2:nilfs2_collection_stage_transition. Ctrl-C to end.
segctord-14875 [003] ...1 28311.067794: nilfs2_collection_stage_transition: sci = ffff8800ce6de000 stage = ST_INIT
segctord-14875 [003] ...1 28311.068139: nilfs2_collection_stage_transition: sci = ffff8800ce6de000 stage = ST_GC
segctord-14875 [003] ...1 28311.068139: nilfs2_collection_stage_transition: sci = ffff8800ce6de000 stage = ST_FILE
segctord-14875 [003] ...1 28311.068486: nilfs2_collection_stage_transition: sci = ffff8800ce6de000 stage = ST_IFILE
segctord-14875 [003] ...1 28311.068540: nilfs2_collection_stage_transition: sci = ffff8800ce6de000 stage = ST_CPFILE
segctord-14875 [003] ...1 28311.068561: nilfs2_collection_stage_transition: sci = ffff8800ce6de000 stage = ST_SUFILE
segctord-14875 [003] ...1 28311.068565: nilfs2_collection_stage_transition: sci = ffff8800ce6de000 stage = ST_DAT
segctord-14875 [003] ...1 28311.068573: nilfs2_collection_stage_transition: sci = ffff8800ce6de000 stage = ST_SR
segctord-14875 [003] ...1 28311.068574: nilfs2_collection_stage_transition: sci = ffff8800ce6de000 stage = ST_DONE
For capturing transition correctly, this patch adds wrappers for the
member scnt of nilfs_cstage. With this change, every transition of the
stage can produce trace event in a correct manner.
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index c6abbad9..ef35404 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -77,6 +77,36 @@
NILFS_ST_DONE,
};
+#define CREATE_TRACE_POINTS
+#include <trace/events/nilfs2.h>
+
+/*
+ * nilfs_sc_cstage_inc(), nilfs_sc_cstage_set(), nilfs_sc_cstage_get() are
+ * wrapper functions of stage count (nilfs_sc_info->sc_stage.scnt). Users of
+ * the variable must use them because transition of stage count must involve
+ * trace events (trace_nilfs2_collection_stage_transition).
+ *
+ * nilfs_sc_cstage_get() isn't required for the above purpose because it doesn't
+ * produce tracepoint events. It is provided just for making the intention
+ * clear.
+ */
+static inline void nilfs_sc_cstage_inc(struct nilfs_sc_info *sci)
+{
+ sci->sc_stage.scnt++;
+ trace_nilfs2_collection_stage_transition(sci);
+}
+
+static inline void nilfs_sc_cstage_set(struct nilfs_sc_info *sci, int next_scnt)
+{
+ sci->sc_stage.scnt = next_scnt;
+ trace_nilfs2_collection_stage_transition(sci);
+}
+
+static inline int nilfs_sc_cstage_get(struct nilfs_sc_info *sci)
+{
+ return sci->sc_stage.scnt;
+}
+
/* State flags of collection */
#define NILFS_CF_NODE 0x0001 /* Collecting node blocks */
#define NILFS_CF_IFILE_STARTED 0x0002 /* IFILE stage has started */
@@ -1062,7 +1092,7 @@
size_t ndone;
int err = 0;
- switch (sci->sc_stage.scnt) {
+ switch (nilfs_sc_cstage_get(sci)) {
case NILFS_ST_INIT:
/* Pre-processes */
sci->sc_stage.flags = 0;
@@ -1071,7 +1101,7 @@
sci->sc_nblk_inc = 0;
sci->sc_curseg->sb_sum.flags = NILFS_SS_LOGBGN;
if (mode == SC_LSEG_DSYNC) {
- sci->sc_stage.scnt = NILFS_ST_DSYNC;
+ nilfs_sc_cstage_set(sci, NILFS_ST_DSYNC);
goto dsync_mode;
}
}
@@ -1079,10 +1109,10 @@
sci->sc_stage.dirty_file_ptr = NULL;
sci->sc_stage.gc_inode_ptr = NULL;
if (mode == SC_FLUSH_DAT) {
- sci->sc_stage.scnt = NILFS_ST_DAT;
+ nilfs_sc_cstage_set(sci, NILFS_ST_DAT);
goto dat_stage;
}
- sci->sc_stage.scnt++; /* Fall through */
+ nilfs_sc_cstage_inc(sci); /* Fall through */
case NILFS_ST_GC:
if (nilfs_doing_gc()) {
head = &sci->sc_gc_inodes;
@@ -1103,7 +1133,7 @@
}
sci->sc_stage.gc_inode_ptr = NULL;
}
- sci->sc_stage.scnt++; /* Fall through */
+ nilfs_sc_cstage_inc(sci); /* Fall through */
case NILFS_ST_FILE:
head = &sci->sc_dirty_files;
ii = list_prepare_entry(sci->sc_stage.dirty_file_ptr, head,
@@ -1125,10 +1155,10 @@
}
sci->sc_stage.dirty_file_ptr = NULL;
if (mode == SC_FLUSH_FILE) {
- sci->sc_stage.scnt = NILFS_ST_DONE;
+ nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
return 0;
}
- sci->sc_stage.scnt++;
+ nilfs_sc_cstage_inc(sci);
sci->sc_stage.flags |= NILFS_CF_IFILE_STARTED;
/* Fall through */
case NILFS_ST_IFILE:
@@ -1136,7 +1166,7 @@
&nilfs_sc_file_ops);
if (unlikely(err))
break;
- sci->sc_stage.scnt++;
+ nilfs_sc_cstage_inc(sci);
/* Creating a checkpoint */
err = nilfs_segctor_create_checkpoint(sci);
if (unlikely(err))
@@ -1147,7 +1177,7 @@
&nilfs_sc_file_ops);
if (unlikely(err))
break;
- sci->sc_stage.scnt++; /* Fall through */
+ nilfs_sc_cstage_inc(sci); /* Fall through */
case NILFS_ST_SUFILE:
err = nilfs_sufile_freev(nilfs->ns_sufile, sci->sc_freesegs,
sci->sc_nfreesegs, &ndone);
@@ -1163,7 +1193,7 @@
&nilfs_sc_file_ops);
if (unlikely(err))
break;
- sci->sc_stage.scnt++; /* Fall through */
+ nilfs_sc_cstage_inc(sci); /* Fall through */
case NILFS_ST_DAT:
dat_stage:
err = nilfs_segctor_scan_file(sci, nilfs->ns_dat,
@@ -1171,10 +1201,10 @@
if (unlikely(err))
break;
if (mode == SC_FLUSH_DAT) {
- sci->sc_stage.scnt = NILFS_ST_DONE;
+ nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
return 0;
}
- sci->sc_stage.scnt++; /* Fall through */
+ nilfs_sc_cstage_inc(sci); /* Fall through */
case NILFS_ST_SR:
if (mode == SC_LSEG_SR) {
/* Appending a super root */
@@ -1184,7 +1214,7 @@
}
/* End of a logical segment */
sci->sc_curseg->sb_sum.flags |= NILFS_SS_LOGEND;
- sci->sc_stage.scnt = NILFS_ST_DONE;
+ nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
return 0;
case NILFS_ST_DSYNC:
dsync_mode:
@@ -1197,7 +1227,7 @@
if (unlikely(err))
break;
sci->sc_curseg->sb_sum.flags |= NILFS_SS_LOGEND;
- sci->sc_stage.scnt = NILFS_ST_DONE;
+ nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
return 0;
case NILFS_ST_DONE:
return 0;
@@ -1442,7 +1472,8 @@
goto failed;
/* The current segment is filled up */
- if (mode != SC_LSEG_SR || sci->sc_stage.scnt < NILFS_ST_CPFILE)
+ if (mode != SC_LSEG_SR ||
+ nilfs_sc_cstage_get(sci) < NILFS_ST_CPFILE)
break;
nilfs_clear_logs(&sci->sc_segbufs);
@@ -1946,7 +1977,7 @@
struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
int err;
- sci->sc_stage.scnt = NILFS_ST_INIT;
+ nilfs_sc_cstage_set(sci, NILFS_ST_INIT);
sci->sc_cno = nilfs->ns_cno;
err = nilfs_segctor_collect_dirty_files(sci, nilfs);
@@ -1974,7 +2005,7 @@
goto failed;
/* Avoid empty segment */
- if (sci->sc_stage.scnt == NILFS_ST_DONE &&
+ if (nilfs_sc_cstage_get(sci) == NILFS_ST_DONE &&
nilfs_segbuf_empty(sci->sc_curseg)) {
nilfs_segctor_abort_construction(sci, nilfs, 1);
goto out;
@@ -1988,7 +2019,7 @@
nilfs_segctor_fill_in_file_bmap(sci);
if (mode == SC_LSEG_SR &&
- sci->sc_stage.scnt >= NILFS_ST_CPFILE) {
+ nilfs_sc_cstage_get(sci) >= NILFS_ST_CPFILE) {
err = nilfs_segctor_fill_in_checkpoint(sci);
if (unlikely(err))
goto failed_to_write;
@@ -2007,7 +2038,7 @@
if (unlikely(err))
goto failed_to_write;
- if (sci->sc_stage.scnt == NILFS_ST_DONE ||
+ if (nilfs_sc_cstage_get(sci) == NILFS_ST_DONE ||
nilfs->ns_blocksize_bits != PAGE_CACHE_SHIFT) {
/*
* At this point, we avoid double buffering
@@ -2020,7 +2051,7 @@
if (err)
goto failed_to_write;
}
- } while (sci->sc_stage.scnt != NILFS_ST_DONE);
+ } while (nilfs_sc_cstage_get(sci) != NILFS_ST_DONE);
out:
nilfs_segctor_drop_written_files(sci, nilfs);