linux - perf mem -D 报告

Question

我使用 perf mem -t load record "commands" 来分析系统内存访问延迟。之后，我运行 perf mem -D report 并得到以下结果:

[root@mdtm-server wenji]# perf mem -D report
# PID, TID, IP, ADDR, LOCAL WEIGHT, DSRC, SYMBOL
 2054  2054 0xffffffff811186bf 0x016ffffe8fbffc804b0    49 0x68100842 /lib/modules/3.12.23/build/vmlinux:perf_event_aux_ctx
2054 2054 0xffffffff81321d6e 0xffff880c7fc87d44 7 0x68100142 /lib/modules/3.12.23/build/vmlinux:ghes_copy_tofrom_phys

“ADDR”、“DSRC”、“SYMBOL”是什么意思？

Answer 1

• IP - 加载/存储指令的 PC；
• SYMBOL - 函数名称，包含此指令 (IP)；
• ADDR - 加载/存储请求的数据的虚拟内存地址(如果没有--phys-data 选项)
• DSRC - “解码源”。

DSRC - 在一些邮件列表中建议检查“SDM Vol 3b 表 18-41(PEBS 记录中数据线性地址信息的布局)”。

内核中也有DSRC编码代码(dse from hw - PEBS; u64 return is dsrc):

http://lxr.free-electrons.com/source/arch/x86/kernel/cpu/perf_event_intel_ds.c?v=4.3#L28

 28 union intel_x86_pebs_dse {
 29         u64 val;
 30         struct {
 31                 unsigned int ld_dse:4;
 32                 unsigned int ld_stlb_miss:1;
 33                 unsigned int ld_locked:1;
 34                 unsigned int ld_reserved:26;
 35         };
 36         struct {
 37                 unsigned int st_l1d_hit:1;
 38                 unsigned int st_reserved1:3;
 39                 unsigned int st_stlb_miss:1;
 40                 unsigned int st_locked:1;
 41                 unsigned int st_reserved2:26;
 42         };
 43 };

http://lxr.free-electrons.com/source/arch/x86/kernel/cpu/perf_event_intel_ds.c?v=4.3#L46

 46 /*
 47  * Map PEBS Load Latency Data Source encodings to generic
 48  * memory data source information
 49  */
 50 #define P(a, b) PERF_MEM_S(a, b)
 51 #define OP_LH (P(OP, LOAD) | P(LVL, HIT))
 52 #define SNOOP_NONE_MISS (P(SNOOP, NONE) | P(SNOOP, MISS))
 53 
 54 static const u64 pebs_data_source[] = {
 55         P(OP, LOAD) | P(LVL, MISS) | P(LVL, L3) | P(SNOOP, NA),/* 0x00:ukn L3 */
 56         OP_LH | P(LVL, L1)  | P(SNOOP, NONE),   /* 0x01: L1 local */
 57         OP_LH | P(LVL, LFB) | P(SNOOP, NONE),   /* 0x02: LFB hit */
 58         OP_LH | P(LVL, L2)  | P(SNOOP, NONE),   /* 0x03: L2 hit */
 59         OP_LH | P(LVL, L3)  | P(SNOOP, NONE),   /* 0x04: L3 hit */
 60         OP_LH | P(LVL, L3)  | P(SNOOP, MISS),   /* 0x05: L3 hit, snoop miss */
 61         OP_LH | P(LVL, L3)  | P(SNOOP, HIT),    /* 0x06: L3 hit, snoop hit */
 62         OP_LH | P(LVL, L3)  | P(SNOOP, HITM),   /* 0x07: L3 hit, snoop hitm */
 63         OP_LH | P(LVL, REM_CCE1) | P(SNOOP, HIT),  /* 0x08: L3 miss snoop hit */
 64         OP_LH | P(LVL, REM_CCE1) | P(SNOOP, HITM), /* 0x09: L3 miss snoop hitm*/
 65         OP_LH | P(LVL, LOC_RAM)  | P(SNOOP, HIT),  /* 0x0a: L3 miss, shared */
 66         OP_LH | P(LVL, REM_RAM1) | P(SNOOP, HIT),  /* 0x0b: L3 miss, shared */
 67         OP_LH | P(LVL, LOC_RAM)  | SNOOP_NONE_MISS,/* 0x0c: L3 miss, excl */
 68         OP_LH | P(LVL, REM_RAM1) | SNOOP_NONE_MISS,/* 0x0d: L3 miss, excl */
 69         OP_LH | P(LVL, IO)  | P(SNOOP, NONE), /* 0x0e: I/O */
 70         OP_LH | P(LVL, UNC) | P(SNOOP, NONE), /* 0x0f: uncached */
 71 };
 72 
 73 static u64 precise_store_data(u64 status)
 74 {
 75         union intel_x86_pebs_dse dse;
 76         u64 val = P(OP, STORE) | P(SNOOP, NA) | P(LVL, L1) | P(TLB, L2);
 77 
 78         dse.val = status;
 79 
 80         /*
 81          * bit 4: TLB access
 82          * 1 = stored missed 2nd level TLB
 83          *
 84          * so it either hit the walker or the OS
 85          * otherwise hit 2nd level TLB
 86          */
 87         if (dse.st_stlb_miss)
 88                 val |= P(TLB, MISS);
 89         else
 90                 val |= P(TLB, HIT);
 91 
 92         /*
 93          * bit 0: hit L1 data cache
 94          * if not set, then all we know is that
 95          * it missed L1D
 96          */
 97         if (dse.st_l1d_hit)
 98                 val |= P(LVL, HIT);
 99         else
100                 val |= P(LVL, MISS);
101 
102         /*
103          * bit 5: Locked prefix
104          */
105         if (dse.st_locked)
106                 val |= P(LOCK, LOCKED);
107 
108         return val;
109 }

dsrc 听起来像是位域中 PERF_MEM_* 宏的几种组合:

http://lxr.free-electrons.com/source/include/uapi/linux/perf_event.h?v=4.3#L878

878 union perf_mem_data_src {
879         __u64 val;
880         struct {
881                 __u64   mem_op:5,       /* type of opcode */
882                         mem_lvl:14,     /* memory hierarchy level */
883                         mem_snoop:5,    /* snoop mode */
884                         mem_lock:2,     /* lock instr */
885                         mem_dtlb:7,     /* tlb access */
886                         mem_rsvd:31;
887         };
888 };
890 /* type of opcode (load/store/prefetch,code) */
891 #define PERF_MEM_OP_NA          0x01 /* not available */
892 #define PERF_MEM_OP_LOAD        0x02 /* load instruction */
893 #define PERF_MEM_OP_STORE       0x04 /* store instruction */
894 #define PERF_MEM_OP_PFETCH      0x08 /* prefetch */
895 #define PERF_MEM_OP_EXEC        0x10 /* code (execution) */
896 #define PERF_MEM_OP_SHIFT       0
897 
898 /* memory hierarchy (memory level, hit or miss) */
899 #define PERF_MEM_LVL_NA         0x01  /* not available */
900 #define PERF_MEM_LVL_HIT        0x02  /* hit level */
901 #define PERF_MEM_LVL_MISS       0x04  /* miss level  */
902 #define PERF_MEM_LVL_L1         0x08  /* L1 */
903 #define PERF_MEM_LVL_LFB        0x10  /* Line Fill Buffer */
904 #define PERF_MEM_LVL_L2         0x20  /* L2 */
905 #define PERF_MEM_LVL_L3         0x40  /* L3 */
906 #define PERF_MEM_LVL_LOC_RAM    0x80  /* Local DRAM */
907 #define PERF_MEM_LVL_REM_RAM1   0x100 /* Remote DRAM (1 hop) */
908 #define PERF_MEM_LVL_REM_RAM2   0x200 /* Remote DRAM (2 hops) */
909 #define PERF_MEM_LVL_REM_CCE1   0x400 /* Remote Cache (1 hop) */
910 #define PERF_MEM_LVL_REM_CCE2   0x800 /* Remote Cache (2 hops) */
911 #define PERF_MEM_LVL_IO         0x1000 /* I/O memory */
912 #define PERF_MEM_LVL_UNC        0x2000 /* Uncached memory */
913 #define PERF_MEM_LVL_SHIFT      5
914 
915 /* snoop mode */
916 #define PERF_MEM_SNOOP_NA       0x01 /* not available */
917 #define PERF_MEM_SNOOP_NONE     0x02 /* no snoop */
918 #define PERF_MEM_SNOOP_HIT      0x04 /* snoop hit */
919 #define PERF_MEM_SNOOP_MISS     0x08 /* snoop miss */
920 #define PERF_MEM_SNOOP_HITM     0x10 /* snoop hit modified */
921 #define PERF_MEM_SNOOP_SHIFT    19
922 
923 /* locked instruction */
924 #define PERF_MEM_LOCK_NA        0x01 /* not available */
925 #define PERF_MEM_LOCK_LOCKED    0x02 /* locked transaction */
926 #define PERF_MEM_LOCK_SHIFT     24
927 
928 /* TLB access */
929 #define PERF_MEM_TLB_NA         0x01 /* not available */
930 #define PERF_MEM_TLB_HIT        0x02 /* hit level */
931 #define PERF_MEM_TLB_MISS       0x04 /* miss level */
932 #define PERF_MEM_TLB_L1         0x08 /* L1 */
933 #define PERF_MEM_TLB_L2         0x10 /* L2 */
934 #define PERF_MEM_TLB_WK         0x20 /* Hardware Walker*/
935 #define PERF_MEM_TLB_OS         0x40 /* OS fault handler */
936 #define PERF_MEM_TLB_SHIFT      26
937 
938 #define PERF_MEM_S(a, s) \
939         (((__u64)PERF_MEM_##a##_##s) << PERF_MEM_##a##_SHIFT)
940