kernel.git/tools/perf/util/intel-pt.c, branch linux-4.4.y

perf intel-pt: Fix "context_switch event has no tid" error

2020-10-29T08:03:06Z

[ Upstream commit 7d537a8d2e76bc4fc71e34545ceaa463ac2cd928 ] A context_switch event can have no tid because pids can be detached from a task while the task is still running (in do_exit()). Note this won't happen with per-task contexts because then tracing stops at perf_event_exit_task() If a task with no tid gets preempted, or a dying task gets preempted and its parent releases it, when it subsequently gets switched back in, Intel PT will not be able to determine what task is running and prints an error "context_switch event has no tid". However, it is not really an error because the task is in kernel space and the decoder can continue to decode successfully. Fix by changing the error to be only a logged message, and make allowance for tid == -1. Example: Using 5.9-rc4 with Preemptible Kernel (Low-Latency Desktop) e.g. $ uname -r 5.9.0-rc4 $ grep PREEMPT .config # CONFIG_PREEMPT_NONE is not set # CONFIG_PREEMPT_VOLUNTARY is not set CONFIG_PREEMPT=y CONFIG_PREEMPT_COUNT=y CONFIG_PREEMPTION=y CONFIG_PREEMPT_RCU=y CONFIG_PREEMPT_NOTIFIERS=y CONFIG_DRM_I915_PREEMPT_TIMEOUT=640 CONFIG_DEBUG_PREEMPT=y # CONFIG_PREEMPT_TRACER is not set # CONFIG_PREEMPTIRQ_DELAY_TEST is not set Before: $ cat forkit.c #include #include #include int main() { pid_t child; int status = 0; child = fork(); if (child == 0) return 123; wait(&status); return 0; } $ gcc -o forkit forkit.c $ sudo ~/bin/perf record --kcore -a -m,64M -e intel_pt/cyc/k & [1] 11016 $ taskset 2 ./forkit $ sudo pkill perf $ [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 17.262 MB perf.data ] [1]+ Terminated sudo ~/bin/perf record --kcore -a -m,64M -e intel_pt/cyc/k $ sudo ~/bin/perf script --show-task-events --show-switch-events --itrace=iqqe-o -C 1 --ns | grep -C 2 forkit context_switch event has no tid taskset 11019 [001] 66663.270045029: 1 instructions:k: ffffffffb1d9f844 strnlen_user+0xb4 ([kernel.kallsyms]) taskset 11019 [001] 66663.270201816: 1 instructions:k: ffffffffb1a83121 unmap_page_range+0x561 ([kernel.kallsyms]) forkit 11019 [001] 66663.270327553: PERF_RECORD_COMM exec: forkit:11019/11019 forkit 11019 [001] 66663.270420028: 1 instructions:k: ffffffffb1db9537 __clear_user+0x27 ([kernel.kallsyms]) forkit 11019 [001] 66663.270648704: 1 instructions:k: ffffffffb18829e6 do_user_addr_fault+0xf6 ([kernel.kallsyms]) forkit 11019 [001] 66663.270833163: 1 instructions:k: ffffffffb230a825 irqentry_exit_to_user_mode+0x15 ([kernel.kallsyms]) forkit 11019 [001] 66663.271092359: 1 instructions:k: ffffffffb1aea3d9 lock_page_memcg+0x9 ([kernel.kallsyms]) forkit 11019 [001] 66663.271207092: PERF_RECORD_FORK(11020:11020):(11019:11019) forkit 11019 [001] 66663.271234775: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 11020/11020 forkit 11020 [001] 66663.271238407: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 11019/11019 forkit 11020 [001] 66663.271312066: 1 instructions:k: ffffffffb1a88140 handle_mm_fault+0x10 ([kernel.kallsyms]) forkit 11020 [001] 66663.271476225: PERF_RECORD_EXIT(11020:11020):(11019:11019) forkit 11020 [001] 66663.271497488: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 11019/11019 forkit 11019 [001] 66663.271500523: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 11020/11020 forkit 11019 [001] 66663.271517241: 1 instructions:k: ffffffffb24012cd error_entry+0x6d ([kernel.kallsyms]) forkit 11019 [001] 66663.271664080: PERF_RECORD_EXIT(11019:11019):(1386:1386) After: $ sudo ~/bin/perf script --show-task-events --show-switch-events --itrace=iqqe-o -C 1 --ns | grep -C 2 forkit taskset 11019 [001] 66663.270045029: 1 instructions:k: ffffffffb1d9f844 strnlen_user+0xb4 ([kernel.kallsyms]) taskset 11019 [001] 66663.270201816: 1 instructions:k: ffffffffb1a83121 unmap_page_range+0x561 ([kernel.kallsyms]) forkit 11019 [001] 66663.270327553: PERF_RECORD_COMM exec: forkit:11019/11019 forkit 11019 [001] 66663.270420028: 1 instructions:k: ffffffffb1db9537 __clear_user+0x27 ([kernel.kallsyms]) forkit 11019 [001] 66663.270648704: 1 instructions:k: ffffffffb18829e6 do_user_addr_fault+0xf6 ([kernel.kallsyms]) forkit 11019 [001] 66663.270833163: 1 instructions:k: ffffffffb230a825 irqentry_exit_to_user_mode+0x15 ([kernel.kallsyms]) forkit 11019 [001] 66663.271092359: 1 instructions:k: ffffffffb1aea3d9 lock_page_memcg+0x9 ([kernel.kallsyms]) forkit 11019 [001] 66663.271207092: PERF_RECORD_FORK(11020:11020):(11019:11019) forkit 11019 [001] 66663.271234775: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 11020/11020 forkit 11020 [001] 66663.271238407: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 11019/11019 forkit 11020 [001] 66663.271312066: 1 instructions:k: ffffffffb1a88140 handle_mm_fault+0x10 ([kernel.kallsyms]) forkit 11020 [001] 66663.271476225: PERF_RECORD_EXIT(11020:11020):(11019:11019) forkit 11020 [001] 66663.271497488: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 11019/11019 forkit 11019 [001] 66663.271500523: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 11020/11020 forkit 11019 [001] 66663.271517241: 1 instructions:k: ffffffffb24012cd error_entry+0x6d ([kernel.kallsyms]) forkit 11019 [001] 66663.271664080: PERF_RECORD_EXIT(11019:11019):(1386:1386) forkit 11019 [001] 66663.271688752: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: -1/-1 :-1 -1 [001] 66663.271692086: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 11019/11019 :-1 -1 [001] 66663.271707466: 1 instructions:k: ffffffffb18eb096 update_load_avg+0x306 ([kernel.kallsyms]) Fixes: 86c2786994bd7c ("perf intel-pt: Add support for PERF_RECORD_SWITCH") Signed-off-by: Adrian Hunter Cc: Andi Kleen Cc: Jiri Olsa Cc: Yu-cheng Yu Link: http://lore.kernel.org/lkml/20200909084923.9096-3-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Sasha Levin

perf intel-pt: Fix "Unexpected indirect branch" error

2018-07-03T09:21:33Z

commit 9fb523363f6e3984457fee95bb7019395384ffa7 upstream. Some Atom CPUs can produce FUP packets that contain NLIP (next linear instruction pointer) instead of CLIP (current linear instruction pointer). That will result in "Unexpected indirect branch" errors. Fix by comparing IP to NLIP in that case. Signed-off-by: Adrian Hunter Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1527762225-26024-5-git-send-email-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Greg Kroah-Hartman

perf intel-pt: Fix sync_switch INTEL_PT_SS_NOT_TRACING

2018-07-03T09:21:33Z

commit dbcb82b93f3e8322891e47472c89e63058b81e99 upstream. sync_switch is a facility to synchronize decoding more closely with the point in the kernel when the context actually switched. In one case, INTEL_PT_SS_NOT_TRACING state was not correctly transitioning to INTEL_PT_SS_TRACING state due to a missing case clause. Add it. Signed-off-by: Adrian Hunter Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1527762225-26024-2-git-send-email-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Greg Kroah-Hartman

perf intel-pt: Fix sync_switch

2018-04-24T07:32:03Z

commit 63d8e38f6ae6c36dd5b5ba0e8c112e8861532ea2 upstream. sync_switch is a facility to synchronize decoding more closely with the point in the kernel when the context actually switched. The flag when sync_switch is enabled was global to the decoding, whereas it is really specific to the CPU. The trace data for different CPUs is put on different queues, so add sync_switch to the intel_pt_queue structure and use that in preference to the global setting in the intel_pt structure. That fixes problems decoding one CPU's trace because sync_switch was disabled on a different CPU's queue. Signed-off-by: Adrian Hunter Cc: Jiri Olsa Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1520431349-30689-3-git-send-email-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Greg Kroah-Hartman

perf intel-pt: Fix overlap detection to identify consecutive buffers correctly

2018-04-24T07:32:03Z

commit 117db4b27bf08dba412faf3924ba55fe970c57b8 upstream. Overlap detection was not not updating the buffer's 'consecutive' flag. Marking buffers consecutive has the advantage that decoding begins from the start of the buffer instead of the first PSB. Fix overlap detection to identify consecutive buffers correctly. Signed-off-by: Adrian Hunter Cc: Jiri Olsa Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1520431349-30689-2-git-send-email-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Greg Kroah-Hartman

perf intel-pt: Fix snapshot overlap detection decoder errors

2016-10-28T07:01:27Z

commit 810c398bc09b2f2dfde52a7d2483a710612c5fb8 upstream. Fix occasional decoder errors decoding trace data collected in snapshot mode. Snapshot mode can take successive snapshots of trace which might overlap. The decoder checks whether there is an overlap but only looks at the current and previous buffer. However buffers that do not contain synchronization (i.e. PSB) packets cannot be decoded or used for overlap checking. That means the decoder actually needs to check overlaps between the current buffer and the previous buffer that contained usable data. Make that change. Signed-off-by: Adrian Hunter Cc: Jiri Olsa Cc: Masami Hiramatsu Cc: Mathieu Poirier Link: http://lkml.kernel.org/r/1474641528-18776-10-git-send-email-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Greg Kroah-Hartman

perf intel-pt: Fix segfault tracing transactions

2016-05-04T21:48:47Z

commit 1342e0b7a6c1a060c593037fbac9f4b717f1cb3b upstream. Tracing a workload that uses transactions gave a seg fault as follows: perf record -e intel_pt// workload perf report Program received signal SIGSEGV, Segmentation fault. 0x000000000054b58c in intel_pt_reset_last_branch_rb (ptq=0x1a36110) at util/intel-pt.c:929 929 ptq->last_branch_rb->nr = 0; (gdb) p ptq->last_branch_rb $1 = (struct branch_stack *) 0x0 (gdb) up 1148 intel_pt_reset_last_branch_rb(ptq); (gdb) l 1143 if (ret) 1144 pr_err("Intel Processor Trace: failed to deliver transaction event 1145 ret); 1146 1147 if (pt->synth_opts.callchain) 1148 intel_pt_reset_last_branch_rb(ptq); 1149 1150 return ret; 1151 } 1152 (gdb) p pt->synth_opts.callchain $2 = true (gdb) (gdb) bt #0 0x000000000054b58c in intel_pt_reset_last_branch_rb (ptq=0x1a36110) #1 0x000000000054c1e0 in intel_pt_synth_transaction_sample (ptq=0x1a36110) #2 0x000000000054c5b2 in intel_pt_sample (ptq=0x1a36110) Caused by checking the 'callchain' flag when it should have been the 'last_branch' flag. Fix that. Reported-by: Andi Kleen Signed-off-by: Adrian Hunter Cc: Jiri Olsa Fixes: f14445ee72c5 ("perf intel-pt: Support generating branch stack") Link: http://lkml.kernel.org/r/1460977068-11566-1-git-send-email-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Greg Kroah-Hartman

perf machine: Add method for common kernel_map(FUNCTION) operation

2015-09-30T21:34:29Z

And it is also a step in the direction of killing the separation of data and text maps in map_groups. Cc: Adrian Hunter Cc: David Ahern Cc: Jiri Olsa Cc: Namhyung Kim Cc: Wang Nan Link: http://lkml.kernel.org/n/tip-rrds86kb3wx5wk8v38v56gw8@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf intel-pt: Add mispred-all config option to aid use with autofdo

2015-09-28T20:21:00Z

autofdo incorrectly expects branch flags to include either mispred or predicted. In fact mispred = predicted = 0 is valid and means the flags are not supported, which they aren't by Intel PT. To make autofdo work, add a config option which will cause Intel PT decoder to set the mispred flag on all branches. Below is an example of using Intel PT with autofdo. The example is also added to the Intel PT documentation. It requires autofdo (https://github.com/google/autofdo) and gcc version 5. The bubble sort example is from the AutoFDO tutorial (https://gcc.gnu.org/wiki/AutoFDO/Tutorial) amended to take the number of elements as a parameter. $ gcc-5 -O3 sort.c -o sort_optimized $ ./sort_optimized 30000 Bubble sorting array of 30000 elements 2254 ms $ cat ~/.perfconfig [intel-pt] mispred-all $ perf record -e intel_pt//u ./sort 3000 Bubble sorting array of 3000 elements 58 ms [ perf record: Woken up 2 times to write data ] [ perf record: Captured and wrote 3.939 MB perf.data ] $ perf inject -i perf.data -o inj --itrace=i100usle --strip $ ./create_gcov --binary=./sort --profile=inj --gcov=sort.gcov -gcov_version=1 $ gcc-5 -O3 -fauto-profile=sort.gcov sort.c -o sort_autofdo $ ./sort_autofdo 30000 Bubble sorting array of 30000 elements 2155 ms Note there is currently no advantage to using Intel PT instead of LBR, but that may change in the future if greater use is made of the data. Signed-off-by: Adrian Hunter Cc: Jiri Olsa Link: http://lkml.kernel.org/r/1443186956-18718-26-git-send-email-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo

perf intel-pt: Support generating branch stack

2015-09-28T19:59:14Z

Add support for generating branch stack context for PT samples. The decoder reports a configurable number of branches as branch context for each sample. Internally it keeps track of them by using a simple sliding window. We also flush the last branch buffer on each sample to avoid overlapping intervals. This is useful for: - Reporting accurate basic block edge frequencies through the perf report branch view - Using with --branch-history to get the wider context of samples - Other users of LBRs Also the Documentation is updated. Examples: Record with Intel PT: perf record -e intel_pt//u ls Branch stacks are used by default if synthesized so: perf report --itrace=ile is the same as: perf report --itrace=ile -b Branch history can be requested also: perf report --itrace=igle --branch-history Based-on-patch-by: Andi Kleen Signed-off-by: Adrian Hunter Cc: Jiri Olsa Link: http://lkml.kernel.org/r/1443186956-18718-15-git-send-email-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo