Re: [PATCH] mm/zsmalloc: add trace events for zs_compact

Minchan Kim
2016-06-08T05:12:49Z

On Wed, Jun 08, 2016 at 09:48:30AM +0800, Ganesh Mahendran wrote:
> Hi, Minchan:
>
> 2016-06-08 8:16 GMT+08:00 Minchan Kim <minchan@kernel.org>:
> > Hello Ganesh,
> >
> > On Tue, Jun 07, 2016 at 04:56:44PM +0800, Ganesh Mahendran wrote:
> >> Currently zsmalloc is widely used in android device.
> >> Sometimes, we want to see how frequently zs_compact is
> >> triggered or how may pages freed by zs_compact(), or which
> >> zsmalloc pool is compacted.
> >>
> >> Most of the time, user can get the brief information from
> >> trace_mm_shrink_slab_[start | end], but in some senario,
> >> they do not use zsmalloc shrinker, but trigger compaction manually.
> >> So add some trace events in zs_compact is convenient. Also we
> >> can add some zsmalloc specific information(pool name, total compact
> >> pages, etc) in zsmalloc trace.
> >
> > Sorry, I cannot understand what's the problem now and what you want to
> > solve. Could you elaborate it a bit?
> >
> > Thanks.
>
> We have backported the zs_compact() to our product(kernel 3.18).
> It is usefull for a longtime running device.
> But there is not a convenient way to get the detailed information
> of zs_comapct() which is usefull for performance optimization.
> Information about how much time zs_compact used, which pool is
> compacted, how many page freed, etc.

You can know how many pages are freed by object compaction via mm_stat
each /sys/block/zram-id/mm_stat. And you can use function_graph to know
how much time zs_compact used.

> With these information, we will know what is going on in zs_comapct.
> And draw the relation between free mem and zs_comapct.
>
> >
> >>
> >> This patch add two trace events for zs_compact(), below the trace log:
> >> -----------------------------
> >> root@land:/ # cat /d/tracing/trace
> >> kswapd0-125 [007] ...1 174.176979: zsmalloc_compact_start: pool zram0
> >> kswapd0-125 [007] ...1 174.181967: zsmalloc_compact_end: pool zram0: 608 pages compacted(total 1794)
> >> kswapd0-125 [000] ...1 184.134475: zsmalloc_compact_start: pool zram0
> >> kswapd0-125 [000] ...1 184.135010: zsmalloc_compact_end: pool zram0: 62 pages compacted(total 1856)
> >> kswapd0-125 [003] ...1 226.927221: zsmalloc_compact_start: pool zram0
> >> kswapd0-125 [003] ...1 226.928575: zsmalloc_compact_end: pool zram0: 250 pages compacted(total 2106)
> >> -----------------------------
> >>
> >> Signed-off-by: Ganesh Mahendran <opensource.ganesh@gmail.com>
> >> ---
> >> include/trace/events/zsmalloc.h | 56 +++++++++++++++++++++++++++++++++++++++++
> >> mm/zsmalloc.c | 10 ++++++++
> >> 2 files changed, 66 insertions(+)
> >> create mode 100644 include/trace/events/zsmalloc.h
> >>
> >> diff --git a/include/trace/events/zsmalloc.h b/include/trace/events/zsmalloc.h
> >> new file mode 100644
> >> index 0000000..3b6f14e
> >> --- /dev/null
> >> +++ b/include/trace/events/zsmalloc.h
> >> @@ -0,0 +1,56 @@
> >> +#undef TRACE_SYSTEM
> >> +#define TRACE_SYSTEM zsmalloc
> >> +
> >> +#if !defined(_TRACE_ZSMALLOC_H) || defined(TRACE_HEADER_MULTI_READ)
> >> +#define _TRACE_ZSMALLOC_H
> >> +
> >> +#include <linux/types.h>
> >> +#include <linux/tracepoint.h>
> >> +
> >> +TRACE_EVENT(zsmalloc_compact_start,
> >> +
> >> + TP_PROTO(const char *pool_name),
> >> +
> >> + TP_ARGS(pool_name),
> >> +
> >> + TP_STRUCT__entry(
> >> + __field(const char *, pool_name)
> >> + ),
> >> +
> >> + TP_fast_assign(
> >> + __entry->pool_name = pool_name;
> >> + ),
> >> +
> >> + TP_printk("pool %s",
> >> + __entry->pool_name)
> >> +);
> >> +
> >> +TRACE_EVENT(zsmalloc_compact_end,
> >> +
> >> + TP_PROTO(const char *pool_name, unsigned long pages_compacted,
> >> + unsigned long pages_total_compacted),
> >> +
> >> + TP_ARGS(pool_name, pages_compacted, pages_total_compacted),
> >> +
> >> + TP_STRUCT__entry(
> >> + __field(const char *, pool_name)
> >> + __field(unsigned long, pages_compacted)
> >> + __field(unsigned long, pages_total_compacted)
> >> + ),
> >> +
> >> + TP_fast_assign(
> >> + __entry->pool_name = pool_name;
> >> + __entry->pages_compacted = pages_compacted;
> >> + __entry->pages_total_compacted = pages_total_compacted;
> >> + ),
> >> +
> >> + TP_printk("pool %s: %ld pages compacted(total %ld)",
> >> + __entry->pool_name,
> >> + __entry->pages_compacted,
> >> + __entry->pages_total_compacted)
> >> +);
> >> +
> >> +#endif /* _TRACE_ZSMALLOC_H */
> >> +
> >> +/* This part must be outside protection */
> >> +#include <trace/define_trace.h>
> >> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> >> index 213d0e1..441b9f7 100644
> >> --- a/mm/zsmalloc.c
> >> +++ b/mm/zsmalloc.c
> >> @@ -30,6 +30,8 @@
> >>
> >> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> >>
> >> +#define CREATE_TRACE_POINTS
> >> +
> >> #include <linux/module.h>
> >> #include <linux/kernel.h>
> >> #include <linux/sched.h>
> >> @@ -52,6 +54,7 @@
> >> #include <linux/mount.h>
> >> #include <linux/compaction.h>
> >> #include <linux/pagemap.h>
> >> +#include <trace/events/zsmalloc.h>
> >>
> >> #define ZSPAGE_MAGIC 0x58
> >>
> >> @@ -2330,6 +2333,9 @@ unsigned long zs_compact(struct zs_pool *pool)
> >> {
> >> int i;
> >> struct size_class *class;
> >> + unsigned long pages_compacted_before = pool->stats.pages_compacted;
> >> +
> >> + trace_zsmalloc_compact_start(pool->name);
> >>
> >> for (i = zs_size_classes - 1; i >= 0; i--) {
> >> class = pool->size_class[i];
> >> @@ -2340,6 +2346,10 @@ unsigned long zs_compact(struct zs_pool *pool)
> >> __zs_compact(pool, class);
> >> }
> >>
> >> + trace_zsmalloc_compact_end(pool->name,
> >> + pool->stats.pages_compacted - pages_compacted_before,
> >> + pool->stats.pages_compacted);
> >> +
> >> return pool->stats.pages_compacted;
> >> }
> >> EXPORT_SYMBOL_GPL(zs_compact);
> >> --
> >> 1.9.1
> >>