From: Minchan Kim Date: Mon, 6 Aug 2018 06:00:19 +0000 (+0900) Subject: mm: introduce per-process mm event tracking feature X-Git-Tag: MMI-QSAS30.62-33-3~49 X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=d3c43f5260bb8cbb54ed914d43da19f2d19e30ea;p=GitHub%2FMotorolaMobilityLLC%2Fkernel-slsi.git mm: introduce per-process mm event tracking feature Linux supports /proc/meminfo and /proc/vmstat stats as memory health metric. Android uses them too. If user see something goes wrong(e.g., sluggish, jank) on their system, they can capture and report system state to developers for debugGing. It shows memory stat at the moment the bug is captured. However, it’s not enough to investigate application's jank problem caused by memory shortage. Because 1. It just shows event count which doesn’t quantify the latency of the application well. Jank could happen by various reasons and one of simple scenario is frame drop for a second. App should draw the frame every 16ms interval. Just number of stats(e.g., allocstall or pgmajfault) couldn't represnt how many of time the app spends for handling the event. 2. At bugreport, dump with vmstat and meminfo is never helpful because it's too late to capture the moment when the problem happens. When the user catch up the problem and try to capture the system state, the problem has already gone. 3. Although we could capture MM stat at the moment bug happens, it couldn't be helpful because MM stats are usually very flucuate so we need historical data rather than one-time snapshot to see MM trend. To solve above problems, this patch introduces per-process, light-weight, mm event stat. Basically, it tracks minor/major faults, reclaim and compaction latency of each process as well as event count and record the data into global buffer. To compromise memory overhead, it doesn't record every MM event of the process to the buffer but just drain accumuated stats every 0.5sec interval to buffer. If there isn't any event, it just skips the recording. For latency data, it keeps average/max latency of each event in that period With that, we could keep useful information with small buffer so that we couldn't miss precious information any longer although the capture time is rather late. This patch introduces basic facility of MM event stat. After all patches in this patchset are applied, outout format is as follows, dumpstate can use it for VM debugGing in future. <...>-1665 [001] d... 217.575173: mm_event_record: min_flt count=203 avg_lat=3 max_lat=58 <...>-1665 [001] d... 217.575183: mm_event_record: maj_flt count=1 avg_lat=1994 max_lat=1994 <...>-1665 [001] d... 217.575184: mm_event_record: kern_alloc count=227 avg_lat=0 max_lat=0 <...>-626 [000] d... 217.578096: mm_event_record: kern_alloc count=4 avg_lat=0 max_lat=0 <...>-6547 [000] .... 217.581913: mm_event_record: min_flt count=7 avg_lat=7 max_lat=20 <...>-6547 [000] .... 217.581955: mm_event_record: kern_alloc count=4 avg_lat=0 max_lat=0 This feature uses event trace for output buffer so that we could use all of general benefit of event trace(e.g., buffer size management, filtering and so on). To prevent overflow of the ring buffer by other random event race, highly suggest that create separate instance of tracing on /sys/kernel/debug/tracing/instances/ I had a concern of adding overhead. Actually, major|compaction/reclaim are already heavy cost so it should be not a concern. Rather than, minor fault and kern alloc would be severe so I tested a micro benchmark to measure minor page fault overhead. Test scenario is create 40 threads and each of them does minor page fault for 25M range(ranges are not overwrapped). I didn't see any noticible regression. Base: fault/wsec avg: 758489.8288 minor faults=13123118, major faults=0 ctx switch=139234 User System Wall fault/wsec 39.55s 41.73s 17.49s 749995.768 minor faults=13123135, major faults=0 ctx switch=139627 User System Wall fault/wsec 34.59s 41.61s 16.95s 773906.976 minor faults=13123061, major faults=0 ctx switch=139254 User System Wall fault/wsec 39.03s 41.55s 16.97s 772966.334 minor faults=13123131, major faults=0 ctx switch=139970 User System Wall fault/wsec 36.71s 42.12s 17.04s 769941.019 minor faults=13123027, major faults=0 ctx switch=138524 User System Wall fault/wsec 42.08s 42.24s 18.08s 725639.047 Base + MM event + event trace enable: fault/wsec avg: 759626.1488 minor faults=13123488, major faults=0 ctx switch=140303 User System Wall fault/wsec 37.66s 42.21s 17.48s 750414.257 minor faults=13123066, major faults=0 ctx switch=138119 User System Wall fault/wsec 36.77s 42.14s 17.49s 750010.107 minor faults=13123505, major faults=0 ctx switch=140021 User System Wall fault/wsec 38.51s 42.50s 17.54s 748022.219 minor faults=13123431, major faults=0 ctx switch=138517 User System Wall fault/wsec 36.74s 41.49s 17.03s 770255.610 minor faults=13122955, major faults=0 ctx switch=137174 User System Wall fault/wsec 40.68s 40.97s 16.83s 779428.551 Mot-CRs-fixed: (CR) Bug: 80168800 Change-Id: I4e69c994f47402766481c58ab5ec2071180964b8 Signed-off-by: Minchan Kim Signed-off-by: Cho KyongHo Reviewed-on: https://gerrit.mot.com/1453718 SME-Granted: SME Approvals Granted SLTApproved: Slta Waiver Tested-by: Jira Key Reviewed-by: Xiangpo Zhao Submit-Approved: Jira Key --- diff --git a/include/linux/mm_event.h b/include/linux/mm_event.h new file mode 100644 index 000000000000..5a9069ea0fa7 --- /dev/null +++ b/include/linux/mm_event.h @@ -0,0 +1,33 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_MM_EVENT_H +#define _LINUX_MM_EVENT_H + +#include +#include + +enum mm_event_type { + MM_MIN_FAULT = 0, + MM_MAJ_FAULT, + MM_COMPACTION, + MM_RECLAIM, + MM_TYPE_NUM, +}; + +struct mm_event_task { + unsigned int count; + unsigned int max_lat; + u64 accm_lat; +} __attribute__ ((packed)); + +struct task_struct; + +#ifdef CONFIG_MM_EVENT_STAT +void mm_event_task_init(struct task_struct *tsk); +void mm_event_start(ktime_t *time); +void mm_event_end(enum mm_event_type event, ktime_t start); +#else +static inline void mm_event_task_init(struct task_struct *tsk) {} +static inline void mm_event_start(ktime_t *time) {} +static inline void mm_event_end(enum mm_event_type event, ktime_t start) {} +#endif /* _LINUX_MM_EVENT_H */ +#endif diff --git a/include/linux/sched.h b/include/linux/sched.h index e99ac4d74444..afcd95fd05e8 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -8,6 +8,7 @@ */ #include +#include #include @@ -985,6 +986,10 @@ struct task_struct { struct rt_mutex_waiter *pi_blocked_on; #endif +#ifdef CONFIG_MM_EVENT_STAT + struct mm_event_task mm_event[MM_TYPE_NUM]; + unsigned long next_period; +#endif #ifdef CONFIG_DEBUG_MUTEXES /* Mutex deadlock detection: */ struct mutex_waiter *blocked_on; diff --git a/include/trace/events/mm_event.h b/include/trace/events/mm_event.h new file mode 100644 index 000000000000..f43dee51f46f --- /dev/null +++ b/include/trace/events/mm_event.h @@ -0,0 +1,49 @@ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM mm_event + +#if !defined(_TRACE_MM_EVENT_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_MM_EVENT_H + +#include +#include +#include + +struct mm_event_task; + +#define show_mm_event_type(type) \ + __print_symbolic(type, \ + { MM_MIN_FAULT, "min_flt" }, \ + { MM_MAJ_FAULT, "maj_flt" }, \ + { MM_COMPACTION, "compaction" }, \ + { MM_RECLAIM, "reclaim" }) + +TRACE_EVENT(mm_event_record, + + TP_PROTO(enum mm_event_type type, struct mm_event_task *record), + + TP_ARGS(type, record), + + TP_STRUCT__entry( + __field(enum mm_event_type, type) + __field(unsigned int, count) + __field(unsigned int, avg_lat) + __field(unsigned int, max_lat) + ), + + TP_fast_assign( + __entry->type = type; + __entry->count = record->count; + __entry->avg_lat = record->accm_lat / record->count; + __entry->max_lat = record->max_lat; + ), + + TP_printk("%s count=%d avg_lat=%u max_lat=%u", + show_mm_event_type(__entry->type), + __entry->count, __entry->avg_lat, + __entry->max_lat) +); + +#endif /* _TRACE_MM_EVENT_H */ + +/* This part must be outside protection */ +#include diff --git a/kernel/fork.c b/kernel/fork.c index 5a34c13ca34b..5d81e13fe127 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1227,6 +1227,7 @@ static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) tsk->min_flt = tsk->maj_flt = 0; tsk->nvcsw = tsk->nivcsw = 0; + mm_event_task_init(tsk); #ifdef CONFIG_DETECT_HUNG_TASK tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; #endif diff --git a/mm/Kconfig b/mm/Kconfig index 656af28886ea..62034754105d 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -621,6 +621,22 @@ config ZSMALLOC_STAT information to userspace via debugfs. If unsure, say N. +config MM_EVENT_STAT + bool "Track per-process MM event" + depends on MMU + help + This option enables per-process mm event stat(e.g., fault, reclaim, + compaction and so on ) with some interval(Default is 0.5sec). + Admin can see the stat from trace file via debugfs(e.g., + /sys/kernel/debug/tracing/trace) + + It includes max/average memory allocation latency for the interval + as well as event count so that admin can see what happens in VM side + (how many each event happens and how much processes spent time for + the MM event). If it's too large, that would be not good situation. + + System can dump the trace into bugreport when user allows the dump. + config GENERIC_EARLY_IOREMAP bool diff --git a/mm/Makefile b/mm/Makefile index 3c72e1ba6348..1430c0b6cf69 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -28,6 +28,9 @@ mmu-$(CONFIG_MMU) := gup.o highmem.o memory.o mincore.o \ rmap.o vmalloc.o +ifdef CONFIG_MM_EVENT_STAT +mmu-$(CONFIG_MMU) += mm_event.o +endif ifdef CONFIG_CROSS_MEMORY_ATTACH mmu-$(CONFIG_MMU) += process_vm_access.o endif diff --git a/mm/mm_event.c b/mm/mm_event.c new file mode 100644 index 000000000000..f2ba7b9004ae --- /dev/null +++ b/mm/mm_event.c @@ -0,0 +1,62 @@ +#include +#include +#include +#include +#include +#include + +#define CREATE_TRACE_POINTS +#include + +void mm_event_task_init(struct task_struct *tsk) +{ + memset(tsk->mm_event, 0, sizeof(tsk->mm_event)); + tsk->next_period = 0; +} + +static void record_stat(void) +{ + if (time_is_before_eq_jiffies(current->next_period)) { + int i; + + for (i = 0; i < MM_TYPE_NUM; i++) { + if (current->mm_event[i].count == 0) + continue; + + trace_mm_event_record(i, ¤t->mm_event[i]); + memset(¤t->mm_event[i], 0, + sizeof(struct mm_event_task)); + } + current->next_period = jiffies + (HZ >> 1); + } +} + +void mm_event_start(ktime_t *time) +{ + *time = ktime_get(); +} + +void mm_event_end(enum mm_event_type event, ktime_t start) +{ + s64 elapsed = ktime_us_delta(ktime_get(), start); + + current->mm_event[event].count++; + current->mm_event[event].accm_lat += elapsed; + if (elapsed > current->mm_event[event].max_lat) + current->mm_event[event].max_lat = elapsed; + record_stat(); +} + +static struct dentry *mm_event_root; + +static int __init mm_event_init(void) +{ + mm_event_root = debugfs_create_dir("mm_event", NULL); + if (!mm_event_root) { + pr_warn("debugfs dir creation failed\n"); + return PTR_ERR(mm_event_root); + } + + return 0; +} +subsys_initcall(mm_event_init);