Re: [PATCH 1/3] Add a new field to struct shrinker

Tony Jones
2016-07-23T04:05:41Z

On 07/22/2016 06:27 PM, Tony Jones wrote:
> On 07/20/2016 07:54 AM, Michal Hocko wrote:
>
>>> Michal, just to make sure I understand you correctly, do you mean that we
>>> could infer the names of the shrinkers by looking at the names of their callbacks?
>>
>> Yes, %ps can then be used for the name of the shrinker structure
>> (assuming it is available).
>
> This is fine for emitting via the ftrace /sys interface, but in order to have the data [name] get
> marshalled thru to perf (for example) you need to add it to the TP_fast_assign entry.
>
> tony

Unfortunately, %ps/%pF doesn't do much (re: Michal's comment "assuming it is available"):

- TP_printk("%pF %p: nid: %d objects to shrink %ld gfp_flags %s pgs_scanned %ld lru_pgs %ld cache items %ld delta %lld total_scan %ld",
+ TP_printk("%pF %p(%ps): nid: %d objects to shrink %ld gfp_flags %s pgs_scanned %ld lru_pgs %ld cache items %ld delta %lld total_scan %ld",
__entry->shrink,
__entry->shr,
+ __entry->shr,
__entry->nid,
__entry->nr_objects_to_shrink,

# cat trace_pipe
bash-1917 [003] ...1 2925.941062: mm_shrink_slab_start: super_cache_scan+0x0/0x1a0 ffff88042bb60cc0(0xffff88042bb60cc0): nid: 0 objects to shrink 0 gfp_flags GFP_KERNEL pgs_scanned 1000 lru_pgs 1000 cache items 4 delta 7 total_scan 7

Otherwise what I was suggesting was something like this to ensure it was correctly marshaled for perf/etc:

diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
--- a/include/trace/events/vmscan.h
+++ b/include/trace/events/vmscan.h
@@ -16,6 +16,8 @@
#define RECLAIM_WB_SYNC 0x0004u /* Unused, all reclaim async */
#define RECLAIM_WB_ASYNC 0x0008u

+#define SHRINKER_NAME_LEN (size_t)32
+
#define show_reclaim_flags(flags) \
(flags) ? __print_flags(flags, "|", \
{RECLAIM_WB_ANON, "RECLAIM_WB_ANON"}, \
@@ -191,6 +193,7 @@ TRACE_EVENT(mm_shrink_slab_start,
TP_STRUCT__entry(
__field(struct shrinker *, shr)
__field(void *, shrink)
+ __array(char, name, SHRINKER_NAME_LEN);
__field(int, nid)
__field(long, nr_objects_to_shrink)
__field(gfp_t, gfp_flags)
@@ -202,6 +205,11 @@ TRACE_EVENT(mm_shrink_slab_start,
),

TP_fast_assign(
+ char sym[KSYM_SYMBOL_LEN];
+
+ sprint_symbol(sym, (unsigned long)shr);
+ strlcpy(__entry->name, sym, SHRINKER_NAME_LEN);
+
__entry->shr = shr;
__entry->shrink = shr->scan_objects;
__entry->nid = sc->nid;
@@ -214,9 +222,10 @@ TRACE_EVENT(mm_shrink_slab_start,
__entry->total_scan = total_scan;
),

- TP_printk("%pF %p: nid: %d objects to shrink %ld gfp_flags %s pgs_scanned %ld lru_pgs %ld cache items %ld delta %lld total_scan %ld",
+ TP_printk("%pF %p(%s): nid: %d objects to shrink %ld gfp_flags %s pgs_scanned %ld lru_pgs %ld cache items %ld delta %lld total_scan %ld",
__entry->shrink,
__entry->shr,
+ __entry->name,
__entry->nid,
__entry->nr_objects_to_shrink,
show_gfp_flags(__entry->gfp_flags),
@@ -236,6 +245,7 @@ TRACE_EVENT(mm_shrink_slab_end,

TP_STRUCT__entry(
__field(struct shrinker *, shr)
+ __array(char, name, SHRINKER_NAME_LEN);
__field(int, nid)
__field(void *, shrink)
__field(long, unused_scan)
@@ -245,6 +255,11 @@ TRACE_EVENT(mm_shrink_slab_end,
),

TP_fast_assign(
+ char sym[KSYM_SYMBOL_LEN];
+
+ sprint_symbol(sym, (unsigned long)shr);
+ strlcpy(__entry->name, sym, SHRINKER_NAME_LEN);
+
__entry->shr = shr;
__entry->nid = nid;
__entry->shrink = shr->scan_objects;
@@ -254,9 +269,10 @@ TRACE_EVENT(mm_shrink_slab_end,
__entry->total_scan = total_scan;
),

- TP_printk("%pF %p: nid: %d unused scan count %ld new scan count %ld total_scan %ld last shrinker return val %d",
+ TP_printk("%pF %p(%pF): nid: %d unused scan count %ld new scan count %ld total_scan %ld last shrinker return val %d",
__entry->shrink,
__entry->shr,
+ __entry->shr,
__entry->nid,
__entry->unused_scan,
__entry->new_scan,