[PATCH v3] nilfs2: add a tracepoint for tracking stage transition of segment construction

Discussion:

Hitoshi Mitake

2014-09-13 15:14:36 UTC

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.

Of course the tracepoint added by this patch is very limited, so we
need to add more points for detailed analysis. This patch is something
like demonstration. If this concept is acceptable for the nilfs
community, I'd like to add more tracepoints and prepare analysis
tools.

Signed-off-by: Hitoshi Mitake <mitake.hitoshi-***@public.gmane.org>
---
fs/nilfs2/segment.c | 71 +++++++++++++++++++++++++++++++------------
fs/nilfs2/segment.h | 3 +-
include/trace/events/nilfs2.h | 50 ++++++++++++++++++++++++++++++
3 files changed, 103 insertions(+), 21 deletions(-)
create mode 100644 include/trace/events/nilfs2.h

v3: undo rename

v2: correct the email address of author

diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index a1a1916..0fcf8e7 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -76,6 +76,36 @@ enum {
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 */
@@ -1055,7 +1085,7 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
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;
@@ -1064,7 +1094,7 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
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;
}
}
@@ -1072,10 +1102,10 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
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;
@@ -1096,7 +1126,7 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
}
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,
@@ -1118,10 +1148,10 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
}
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:
@@ -1129,7 +1159,7 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
&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))
@@ -1140,7 +1170,7 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
&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);
@@ -1156,7 +1186,7 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
&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,
@@ -1164,10 +1194,10 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
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 */
@@ -1177,7 +1207,7 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
}
/* 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:
@@ -1190,7 +1220,7 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
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;
@@ -1435,7 +1465,8 @@ static int nilfs_segctor_collect(struct nilfs_sc_info *sci,
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);
@@ -1924,7 +1955,7 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
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);
@@ -1952,7 +1983,7 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
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;
@@ -1966,7 +1997,7 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
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;
@@ -1985,7 +2016,7 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
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
@@ -1998,7 +2029,7 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
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);
diff --git a/fs/nilfs2/segment.h b/fs/nilfs2/segment.h
index 38a1d00..b1abece 100644
--- a/fs/nilfs2/segment.h
+++ b/fs/nilfs2/segment.h
@@ -66,7 +66,8 @@ struct nilfs_recovery_info {

/**
* struct nilfs_cstage - Context of collection stage
- * @scnt: Stage count
+ * @scnt: Stage count, must be accessed via wrappers:
+ * nilfs_sc_cstage_inc(), nilfs_sc_cstage_set(), nilfs_sc_cstage_get()
* @flags: State flags
* @dirty_file_ptr: Pointer on dirty_files list, or inode of a target file
* @gc_inode_ptr: Pointer on the list of gc-inodes
diff --git a/include/trace/events/nilfs2.h b/include/trace/events/nilfs2.h
new file mode 100644
index 0000000..285d5f3
--- /dev/null
+++ b/include/trace/events/nilfs2.h
@@ -0,0 +1,50 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM nilfs2
+
+#if !defined(_TRACE_NILFS2_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_NILFS2_H
+
+#include <linux/tracepoint.h>
+
+struct nilfs_sc_info;
+
+#define show_collection_stage(type) \
+ __print_symbolic(type, \
+ { NILFS_ST_INIT, "ST_INIT" }, \
+ { NILFS_ST_GC, "ST_GC" }, \
+ { NILFS_ST_FILE, "ST_FILE" }, \
+ { NILFS_ST_IFILE, "ST_IFILE" }, \
+ { NILFS_ST_CPFILE, "ST_CPFILE" }, \
+ { NILFS_ST_SUFILE, "ST_SUFILE" }, \
+ { NILFS_ST_DAT, "ST_DAT" }, \
+ { NILFS_ST_SR, "ST_SR" }, \
+ { NILFS_ST_DSYNC, "ST_DSYNC" }, \
+ { NILFS_ST_DONE, "ST_DONE"})
+
+TRACE_EVENT(nilfs2_collection_stage_transition,
+
+ TP_PROTO(struct nilfs_sc_info *sci),
+
+ TP_ARGS(sci),
+
+ TP_STRUCT__entry(
+ __field(void *, sci)
+ __field(int, stage)
+ ),
+
+ TP_fast_assign(
+ __entry->sci = sci;
+ __entry->stage = sci->sc_stage.scnt;
+ ),
+
+ TP_printk("sci = %p, stage = %s",
+ __entry->sci,
+ show_collection_stage(__entry->stage))
+);
+
+#endif /* _TRACE_NILFS2_H */
+
+/* This part must be outside protection */
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE nilfs2
+#include <trace/define_trace.h>

--
1.9.1

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Ryusuke Konishi

2014-09-14 04:09:13 UTC

Permalink

Post by Hitoshi Mitake
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.
Of course the tracepoint added by this patch is very limited, so we
need to add more points for detailed analysis. This patch is something
like demonstration. If this concept is acceptable for the nilfs
community, I'd like to add more tracepoints and prepare analysis
tools.
---
fs/nilfs2/segment.c | 71 +++++++++++++++++++++++++++++++------------
fs/nilfs2/segment.h | 3 +-
include/trace/events/nilfs2.h | 50 ++++++++++++++++++++++++++++++
3 files changed, 103 insertions(+), 21 deletions(-)
create mode 100644 include/trace/events/nilfs2.h
v3: undo rename
v2: correct the email address of author

<snip>

Looks good. I pushed out this patch as "tracepoints" branch of
nilfs2.git[1].

If you hope it to be sent to upstream separately at this time, please
let me know. (In that case, the following description should be
revised to be ready for mainline merge).

Post by Hitoshi Mitake
Of course the tracepoint added by this patch is very limited, so we
need to add more points for detailed analysis. This patch is something
like demonstration. If this concept is acceptable for the nilfs
community, I'd like to add more tracepoints and prepare analysis
tools.

Otherwise, I'll keep it in the tracepoints branch for now.

[1] https://github.com/konis/nilfs2.git

Thanks,
Ryusuke Konishi

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Hitoshi Mitake

2014-09-14 07:20:33 UTC

Permalink

On Sun, Sep 14, 2014 at 1:09 PM, Ryusuke Konishi

Post by Ryusuke Konishi

<snip>
Looks good. I pushed out this patch as "tracepoints" branch of
nilfs2.git[1].
If you hope it to be sent to upstream separately at this time, please
let me know. (In that case, the following description should be
revised to be ready for mainline merge).

Otherwise, I'll keep it in the tracepoints branch for now.

Thanks a lot for your review and pushing. The change for tracepoints
doesn't need to be sent to upstream immediately. I'll enhance the
feature for a while on the tracepoints branch.

Thanks,
Hitoshi

Post by Ryusuke Konishi
[1] https://github.com/konis/nilfs2.git
Thanks,
Ryusuke Konishi

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