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

Ganesh Mahendran
2016-06-08T01:48:34Z

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.
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
>>