2023-09-24 22:06:47

by Jaewon Kim

[permalink] [raw]
Subject: [PATCH v3] vmscan: add trace events for lru_gen

As the legacy lru provides, the lru_gen needs some trace events for
debugging.

This commit introduces 2 trace events.
trace_mm_vmscan_lru_gen_scan
trace_mm_vmscan_lru_gen_evict

Each event is similar to the following legacy events.
trace_mm_vmscan_lru_isolate,
trace_mm_vmscan_lru_shrink_[in]active

Here's an example
mm_vmscan_lru_gen_scan: isolate_mode=0 classzone=1 order=9 nr_requested=4096 nr_scanned=431 nr_skipped=0 nr_taken=55 lru=anon
mm_vmscan_lru_gen_evict: nid=0 nr_reclaimed=42 nr_dirty=0 nr_writeback=0 nr_congested=0 nr_immediate=0 nr_activate_anon=13 nr_activate_file=0 nr_ref_keep=0 nr_unmap_fail=0 priority=2 flags=RECLAIM_WB_ANON|RECLAIM_WB_ASYNC
mm_vmscan_lru_gen_scan: isolate_mode=0 classzone=1 order=9 nr_requested=4096 nr_scanned=66 nr_skipped=0 nr_taken=64 lru=file
mm_vmscan_lru_gen_evict: nid=0 nr_reclaimed=62 nr_dirty=0 nr_writeback=0 nr_congested=0 nr_immediate=0 nr_activate_anon=0 nr_activate_file=2 nr_ref_keep=0 nr_unmap_fail=0 priority=2 flags=RECLAIM_WB_FILE|RECLAIM_WB_ASYNC

Signed-off-by: Jaewon Kim <[email protected]>
Reviewed-by: Steven Rostedt (Google) <[email protected]>
Reviewed-by: T.J. Mercier <[email protected]>
---
v3: change printk format
v2: use condition and make it aligned
v1: introduce trace events
---
include/trace/events/mmflags.h | 5 ++
include/trace/events/vmscan.h | 98 ++++++++++++++++++++++++++++++++++
mm/vmscan.c | 17 ++++--
3 files changed, 115 insertions(+), 5 deletions(-)

diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index 1478b9dd05fa..44e9b38f83e7 100644
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -274,6 +274,10 @@ IF_HAVE_VM_SOFTDIRTY(VM_SOFTDIRTY, "softdirty" ) \
EM (LRU_ACTIVE_FILE, "active_file") \
EMe(LRU_UNEVICTABLE, "unevictable")

+#define LRU_GEN_NAMES \
+ EM (LRU_GEN_ANON, "anon") \
+ EMe(LRU_GEN_FILE, "file")
+
/*
* First define the enums in the above macros to be exported to userspace
* via TRACE_DEFINE_ENUM().
@@ -288,6 +292,7 @@ COMPACTION_PRIORITY
/* COMPACTION_FEEDBACK are defines not enums. Not needed here. */
ZONE_TYPE
LRU_NAMES
+LRU_GEN_NAMES

/*
* Now redefine the EM() and EMe() macros to map the enums to the strings
diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
index d2123dd960d5..12eee5558016 100644
--- a/include/trace/events/vmscan.h
+++ b/include/trace/events/vmscan.h
@@ -327,6 +327,57 @@ TRACE_EVENT(mm_vmscan_lru_isolate,
__print_symbolic(__entry->lru, LRU_NAMES))
);

+TRACE_EVENT_CONDITION(mm_vmscan_lru_gen_scan,
+ TP_PROTO(int highest_zoneidx,
+ int order,
+ unsigned long nr_requested,
+ unsigned long nr_scanned,
+ unsigned long nr_skipped,
+ unsigned long nr_taken,
+ isolate_mode_t isolate_mode,
+ int lru),
+
+ TP_ARGS(highest_zoneidx, order, nr_requested, nr_scanned, nr_skipped, nr_taken, isolate_mode, lru),
+
+ TP_CONDITION(nr_scanned),
+
+ TP_STRUCT__entry(
+ __field(int, highest_zoneidx)
+ __field(int, order)
+ __field(unsigned long, nr_requested)
+ __field(unsigned long, nr_scanned)
+ __field(unsigned long, nr_skipped)
+ __field(unsigned long, nr_taken)
+ __field(unsigned int, isolate_mode)
+ __field(int, lru)
+ ),
+
+ TP_fast_assign(
+ __entry->highest_zoneidx = highest_zoneidx;
+ __entry->order = order;
+ __entry->nr_requested = nr_requested;
+ __entry->nr_scanned = nr_scanned;
+ __entry->nr_skipped = nr_skipped;
+ __entry->nr_taken = nr_taken;
+ __entry->isolate_mode = (__force unsigned int)isolate_mode;
+ __entry->lru = lru;
+ ),
+
+ /*
+ * classzone is previous name of the highest_zoneidx.
+ * Reason not to change it is the ABI requirement of the tracepoint.
+ */
+ TP_printk("isolate_mode=%u classzone=%d order=%d nr_requested=%lu nr_scanned=%lu nr_skipped=%lu nr_taken=%lu lru=%s",
+ __entry->isolate_mode,
+ __entry->highest_zoneidx,
+ __entry->order,
+ __entry->nr_requested,
+ __entry->nr_scanned,
+ __entry->nr_skipped,
+ __entry->nr_taken,
+ __print_symbolic(__entry->lru, LRU_GEN_NAMES))
+);
+
TRACE_EVENT(mm_vmscan_write_folio,

TP_PROTO(struct folio *folio),
@@ -437,6 +488,53 @@ TRACE_EVENT(mm_vmscan_lru_shrink_active,
show_reclaim_flags(__entry->reclaim_flags))
);

+TRACE_EVENT(mm_vmscan_lru_gen_evict,
+
+ TP_PROTO(int nid, unsigned long nr_reclaimed,
+ struct reclaim_stat *stat, int priority, int file),
+
+ TP_ARGS(nid, nr_reclaimed, stat, priority, file),
+
+ TP_STRUCT__entry(
+ __field(unsigned long, nr_reclaimed)
+ __field(unsigned long, nr_dirty)
+ __field(unsigned long, nr_writeback)
+ __field(unsigned long, nr_congested)
+ __field(unsigned long, nr_immediate)
+ __field(unsigned int, nr_activate0)
+ __field(unsigned int, nr_activate1)
+ __field(unsigned long, nr_ref_keep)
+ __field(unsigned long, nr_unmap_fail)
+ __field(int, nid)
+ __field(int, priority)
+ __field(int, reclaim_flags)
+ ),
+
+ TP_fast_assign(
+ __entry->nid = nid;
+ __entry->nr_reclaimed = nr_reclaimed;
+ __entry->nr_dirty = stat->nr_dirty;
+ __entry->nr_writeback = stat->nr_writeback;
+ __entry->nr_congested = stat->nr_congested;
+ __entry->nr_immediate = stat->nr_immediate;
+ __entry->nr_activate0 = stat->nr_activate[0];
+ __entry->nr_activate1 = stat->nr_activate[1];
+ __entry->nr_ref_keep = stat->nr_ref_keep;
+ __entry->nr_unmap_fail = stat->nr_unmap_fail;
+ __entry->priority = priority;
+ __entry->reclaim_flags = trace_reclaim_flags(file);
+ ),
+
+ TP_printk("nid=%d nr_reclaimed=%lu nr_dirty=%lu nr_writeback=%lu nr_congested=%lu nr_immediate=%lu nr_activate_anon=%u nr_activate_file=%u nr_ref_keep=%lu nr_unmap_fail=%lu priority=%d flags=%s",
+ __entry->nid, __entry->nr_reclaimed,
+ __entry->nr_dirty, __entry->nr_writeback,
+ __entry->nr_congested, __entry->nr_immediate,
+ __entry->nr_activate0, __entry->nr_activate1,
+ __entry->nr_ref_keep, __entry->nr_unmap_fail,
+ __entry->priority,
+ show_reclaim_flags(__entry->reclaim_flags))
+);
+
TRACE_EVENT(mm_vmscan_node_reclaim_begin,

TP_PROTO(int nid, int order, gfp_t gfp_flags),
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6f13394b112e..f453a0f8ceef 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -5005,6 +5005,7 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
int sorted = 0;
int scanned = 0;
int isolated = 0;
+ int skipped = 0;
int remaining = MAX_LRU_BATCH;
struct lru_gen_folio *lrugen = &lruvec->lrugen;
struct mem_cgroup *memcg = lruvec_memcg(lruvec);
@@ -5018,7 +5019,7 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,

for (i = MAX_NR_ZONES; i > 0; i--) {
LIST_HEAD(moved);
- int skipped = 0;
+ int skipped_zone = 0;
int zone = (sc->reclaim_idx + i) % MAX_NR_ZONES;
struct list_head *head = &lrugen->folios[gen][type][zone];

@@ -5040,16 +5041,17 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
isolated += delta;
} else {
list_move(&folio->lru, &moved);
- skipped += delta;
+ skipped_zone += delta;
}

- if (!--remaining || max(isolated, skipped) >= MIN_LRU_BATCH)
+ if (!--remaining || max(isolated, skipped_zone) >= MIN_LRU_BATCH)
break;
}

- if (skipped) {
+ if (skipped_zone) {
list_splice(&moved, head);
- __count_zid_vm_events(PGSCAN_SKIP, zone, skipped);
+ __count_zid_vm_events(PGSCAN_SKIP, zone, skipped_zone);
+ skipped += skipped_zone;
}

if (!remaining || isolated >= MIN_LRU_BATCH)
@@ -5065,6 +5067,9 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
__count_memcg_events(memcg, PGREFILL, sorted);
__count_vm_events(PGSCAN_ANON + type, isolated);

+ trace_mm_vmscan_lru_gen_scan(sc->reclaim_idx, sc->order, MAX_LRU_BATCH,
+ scanned, skipped, isolated,
+ sc->may_unmap ? 0 : ISOLATE_UNMAPPED, type);
/*
* There might not be eligible folios due to reclaim_idx. Check the
* remaining to prevent livelock if it's not making progress.
@@ -5194,6 +5199,8 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
retry:
reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false);
sc->nr_reclaimed += reclaimed;
+ trace_mm_vmscan_lru_gen_evict(pgdat->node_id, reclaimed, &stat,
+ sc->priority, type);

list_for_each_entry_safe_reverse(folio, next, &list, lru) {
if (!folio_evictable(folio)) {
--
2.17.1


2023-09-25 21:40:04

by SeongJae Park

[permalink] [raw]
Subject: Re: [PATCH v3] vmscan: add trace events for lru_gen

Hello,

On Sun, 24 Sep 2023 23:23:43 +0900 Jaewon Kim <[email protected]> wrote:

> As the legacy lru provides, the lru_gen needs some trace events for
> debugging.
>
> This commit introduces 2 trace events.
> trace_mm_vmscan_lru_gen_scan
> trace_mm_vmscan_lru_gen_evict
>
> Each event is similar to the following legacy events.
> trace_mm_vmscan_lru_isolate,
> trace_mm_vmscan_lru_shrink_[in]active
>
> Here's an example
> mm_vmscan_lru_gen_scan: isolate_mode=0 classzone=1 order=9 nr_requested=4096 nr_scanned=431 nr_skipped=0 nr_taken=55 lru=anon
> mm_vmscan_lru_gen_evict: nid=0 nr_reclaimed=42 nr_dirty=0 nr_writeback=0 nr_congested=0 nr_immediate=0 nr_activate_anon=13 nr_activate_file=0 nr_ref_keep=0 nr_unmap_fail=0 priority=2 flags=RECLAIM_WB_ANON|RECLAIM_WB_ASYNC
> mm_vmscan_lru_gen_scan: isolate_mode=0 classzone=1 order=9 nr_requested=4096 nr_scanned=66 nr_skipped=0 nr_taken=64 lru=file
> mm_vmscan_lru_gen_evict: nid=0 nr_reclaimed=62 nr_dirty=0 nr_writeback=0 nr_congested=0 nr_immediate=0 nr_activate_anon=0 nr_activate_file=2 nr_ref_keep=0 nr_unmap_fail=0 priority=2 flags=RECLAIM_WB_FILE|RECLAIM_WB_ASYNC
>
> Signed-off-by: Jaewon Kim <[email protected]>
> Reviewed-by: Steven Rostedt (Google) <[email protected]>
> Reviewed-by: T.J. Mercier <[email protected]>
> ---
> v3: change printk format
> v2: use condition and make it aligned
> v1: introduce trace events
> ---
> include/trace/events/mmflags.h | 5 ++
> include/trace/events/vmscan.h | 98 ++++++++++++++++++++++++++++++++++
> mm/vmscan.c | 17 ++++--
> 3 files changed, 115 insertions(+), 5 deletions(-)
>
> diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
> index 1478b9dd05fa..44e9b38f83e7 100644
> --- a/include/trace/events/mmflags.h
> +++ b/include/trace/events/mmflags.h
> @@ -274,6 +274,10 @@ IF_HAVE_VM_SOFTDIRTY(VM_SOFTDIRTY, "softdirty" ) \
> EM (LRU_ACTIVE_FILE, "active_file") \
> EMe(LRU_UNEVICTABLE, "unevictable")
>
> +#define LRU_GEN_NAMES \
> + EM (LRU_GEN_ANON, "anon") \
> + EMe(LRU_GEN_FILE, "file")
> +

I found this patchset makes build fails when !CONFIG_LRU_GEN, like below:

In file included from /linux/include/trace/trace_events.h:27,
from /linux/include/trace/define_trace.h:102,
from /linux/include/trace/events/oom.h:195,
from /linux/mm/oom_kill.c:53:
/linux/include/trace/events/mmflags.h:278:7: error: ‘LRU_GEN_ANON’ undeclared here (not in a function); did you mean ‘LRU_GEN_PGOFF’?
278 | EM (LRU_GEN_ANON, "anon") \
| ^~~~~~~~~~~~

Maybe some config checks are needed?


Thanks,
SJ

[...]

2023-09-26 09:20:56

by Jaewon Kim

[permalink] [raw]
Subject: RE: [PATCH v3] vmscan: add trace events for lru_gen

>Hello,
>
>On Sun, 24 Sep 2023 23:23:43 +0900 Jaewon Kim <[email protected]> wrote:
>
>> As the legacy lru provides, the lru_gen needs some trace events for
>> debugging.
>>
>> This commit introduces 2 trace events.
>> trace_mm_vmscan_lru_gen_scan
>> trace_mm_vmscan_lru_gen_evict
>>
>> Each event is similar to the following legacy events.
>> trace_mm_vmscan_lru_isolate,
>> trace_mm_vmscan_lru_shrink_[in]active
>>
>> Here's an example
>> mm_vmscan_lru_gen_scan: isolate_mode=0 classzone=1 order=9 nr_requested=4096 nr_scanned=431 nr_skipped=0 nr_taken=55 lru=anon
>> mm_vmscan_lru_gen_evict: nid=0 nr_reclaimed=42 nr_dirty=0 nr_writeback=0 nr_congested=0 nr_immediate=0 nr_activate_anon=13 nr_activate_file=0 nr_ref_keep=0 nr_unmap_fail=0 priority=2 flags=RECLAIM_WB_ANON|RECLAIM_WB_ASYNC
>> mm_vmscan_lru_gen_scan: isolate_mode=0 classzone=1 order=9 nr_requested=4096 nr_scanned=66 nr_skipped=0 nr_taken=64 lru=file
>> mm_vmscan_lru_gen_evict: nid=0 nr_reclaimed=62 nr_dirty=0 nr_writeback=0 nr_congested=0 nr_immediate=0 nr_activate_anon=0 nr_activate_file=2 nr_ref_keep=0 nr_unmap_fail=0 priority=2 flags=RECLAIM_WB_FILE|RECLAIM_WB_ASYNC
>>
>> Signed-off-by: Jaewon Kim <[email protected]>
>> Reviewed-by: Steven Rostedt (Google) <[email protected]>
>> Reviewed-by: T.J. Mercier <[email protected]>
>> ---
>> v3: change printk format
>> v2: use condition and make it aligned
>> v1: introduce trace events
>> ---
>> include/trace/events/mmflags.h | 5 ++
>> include/trace/events/vmscan.h | 98 ++++++++++++++++++++++++++++++++++
>> mm/vmscan.c | 17 ++++--
>> 3 files changed, 115 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
>> index 1478b9dd05fa..44e9b38f83e7 100644
>> --- a/include/trace/events/mmflags.h
>> +++ b/include/trace/events/mmflags.h
>> @@ -274,6 +274,10 @@ IF_HAVE_VM_SOFTDIRTY(VM_SOFTDIRTY, "softdirty" ) \
>> EM (LRU_ACTIVE_FILE, "active_file") \
>> EMe(LRU_UNEVICTABLE, "unevictable")
>>
>> +#define LRU_GEN_NAMES \
>> + EM (LRU_GEN_ANON, "anon") \
>> + EMe(LRU_GEN_FILE, "file")
>> +
>
>I found this patchset makes build fails when !CONFIG_LRU_GEN, like below:
>
> In file included from /linux/include/trace/trace_events.h:27,
> from /linux/include/trace/define_trace.h:102,
> from /linux/include/trace/events/oom.h:195,
> from /linux/mm/oom_kill.c:53:
> /linux/include/trace/events/mmflags.h:278:7: error: ‘LRU_GEN_ANON’ undeclared here (not in a function); did you mean ‘LRU_GEN_PGOFF’?
> 278 | EM (LRU_GEN_ANON, "anon") \
> | ^~~~~~~~~~~~
>
>Maybe some config checks are needed?

Sorry and thank you for your comment.
I think I need to wrap with CONFIG_LRU_GEN
Adding #ifdef CONFIG_LRU_GEN even to vmscan.c seems not nice though.

Additionally I had to remove isolate_mode to be compatible with
mm, vmscan: remove ISOLATE_UNMAPPED
https://lore.kernel.org/linux-mm/[email protected]/

Here's what I changed on top of this v3 patch.
I'm trying to find a way not to use ifdef CONFIG_LRU_GEN in vmscan.c



--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -274,9 +274,11 @@ IF_HAVE_VM_SOFTDIRTY(VM_SOFTDIRTY, "softdirty" ) \
EM (LRU_ACTIVE_FILE, "active_file") \
EMe(LRU_UNEVICTABLE, "unevictable")

+#ifdef CONFIG_LRU_GEN
#define LRU_GEN_NAMES \
EM (LRU_GEN_ANON, "anon") \
EMe(LRU_GEN_FILE, "file")
+#endif

/*
* First define the enums in the above macros to be exported to userspace
@@ -292,7 +294,9 @@ COMPACTION_PRIORITY
/* COMPACTION_FEEDBACK are defines not enums. Not needed here. */
ZONE_TYPE
LRU_NAMES
+#ifdef CONFIG_LRU_GEN
LRU_GEN_NAMES
+#endif

/*
* Now redefine the EM() and EMe() macros to map the enums to the strings
diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
index e7230fa8bda1..ba99182d6558 100644
--- a/include/trace/events/vmscan.h
+++ b/include/trace/events/vmscan.h
@@ -323,6 +323,7 @@ TRACE_EVENT(mm_vmscan_lru_isolate,
__print_symbolic(__entry->lru, LRU_NAMES))
);

+#ifdef CONFIG_LRU_GEN
TRACE_EVENT_CONDITION(mm_vmscan_lru_gen_scan,
TP_PROTO(int highest_zoneidx,
int order,
@@ -330,10 +331,9 @@ TRACE_EVENT_CONDITION(mm_vmscan_lru_gen_scan,
unsigned long nr_scanned,
unsigned long nr_skipped,
unsigned long nr_taken,
- isolate_mode_t isolate_mode,
int lru),

- TP_ARGS(highest_zoneidx, order, nr_requested, nr_scanned, nr_skipped, nr_taken, isolate_mode, lru),
+ TP_ARGS(highest_zoneidx, order, nr_requested, nr_scanned, nr_skipped, nr_taken, lru),

TP_CONDITION(nr_scanned),

@@ -344,7 +344,6 @@ TRACE_EVENT_CONDITION(mm_vmscan_lru_gen_scan,
__field(unsigned long, nr_scanned)
__field(unsigned long, nr_skipped)
__field(unsigned long, nr_taken)
- __field(unsigned int, isolate_mode)
__field(int, lru)
),

@@ -355,7 +354,6 @@ TRACE_EVENT_CONDITION(mm_vmscan_lru_gen_scan,
__entry->nr_scanned = nr_scanned;
__entry->nr_skipped = nr_skipped;
__entry->nr_taken = nr_taken;
- __entry->isolate_mode = (__force unsigned int)isolate_mode;
__entry->lru = lru;
),

@@ -363,7 +361,7 @@ TRACE_EVENT_CONDITION(mm_vmscan_lru_gen_scan,
* classzone is previous name of the highest_zoneidx.
* Reason not to change it is the ABI requirement of the tracepoint.
*/
- TP_printk("isolate_mode=%u classzone=%d order=%d nr_requested=%lu nr_scanned=%lu nr_skipped=%lu nr_taken=%lu lru=%s",
+ TP_printk("classzone=%d order=%d nr_requested=%lu nr_scanned=%lu nr_skipped=%lu nr_taken=%lu lru=%s",
__entry->isolate_mode,
__entry->highest_zoneidx,
__entry->order,
@@ -373,6 +371,7 @@ TRACE_EVENT_CONDITION(mm_vmscan_lru_gen_scan,
__entry->nr_taken,
__print_symbolic(__entry->lru, LRU_GEN_NAMES))
);
+#endif

TRACE_EVENT(mm_vmscan_write_folio,

@@ -484,6 +483,7 @@ TRACE_EVENT(mm_vmscan_lru_shrink_active,
show_reclaim_flags(__entry->reclaim_flags))
);

+#ifdef CONFIG_LRU_GEN
TRACE_EVENT(mm_vmscan_lru_gen_evict,

TP_PROTO(int nid, unsigned long nr_reclaimed,
@@ -530,6 +530,7 @@ TRACE_EVENT(mm_vmscan_lru_gen_evict,
__entry->priority,
show_reclaim_flags(__entry->reclaim_flags))
);
+#endif

TRACE_EVENT(mm_vmscan_node_reclaim_begin,

diff --git a/mm/vmscan.c b/mm/vmscan.c
index dbfacf79b42c..d26e1d2610ca 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4390,9 +4390,10 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
__count_memcg_events(memcg, PGREFILL, sorted);
__count_vm_events(PGSCAN_ANON + type, isolated);

+#ifdef CONFIG_LRU_GEN
trace_mm_vmscan_lru_gen_scan(sc->reclaim_idx, sc->order, MAX_LRU_BATCH,
- scanned, skipped, isolated,
- sc->may_unmap ? 0 : ISOLATE_UNMAPPED, type);
+ scanned, skipped, isolated, type);
+#endif
/*
* There might not be eligible folios due to reclaim_idx. Check the
* remaining to prevent livelock if it's not making progress.
@@ -4522,8 +4523,10 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
retry:
reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false);
sc->nr_reclaimed += reclaimed;
+#ifdef CONFIG_LRU_GEN
trace_mm_vmscan_lru_gen_evict(pgdat->node_id, reclaimed, &stat,
sc->priority, type);
+#endif

list_for_each_entry_safe_reverse(folio, next, &list, lru) {
if (!folio_evictable(folio)) {


Thank you

>
>
>Thanks,
>SJ