Re: [PATCH RFC 5/7] perf pmu: Support matching by sysid

From: John Garry
Date: Wed Feb 12 2020 - 05:08:51 EST

On 11/02/2020 15:07, John Garry wrote:
On 11/02/2020 13:47, Jiri Olsa wrote:

Hi Jirka,

+
+ÂÂÂ return buf;
+}
+

I have another series to add kernel support for a system identifier sysfs
entry, which I sent after this series:

https://lore.kernel.org/linux-acpi/1580210059-199540-1-git-send-email-john.garry@xxxxxxxxxx/

It is different to what I am relying on here - it uses a kernel soc driver
for firmware ACPI PPTT identifier. Progress is somewhat blocked at the
moment however and I may have to use a different method:

https://lore.kernel.org/linux-acpi/20200128123415.GB36168@bogus/

I'll try to check ;-)

Summary is that there exists an ACPI firmware field which we could expose to userspace via sysfs - this would provide the system id. However there is a proposal to deprecate it in the ACPI standard and, as such, would prefer that we don't add kernel support for it at this stage.

So I am evaluating the alternative in the meantime, which again is some firmware method which should allow us to expose a system id to userspace via sysfs. Unfortunately this is arm specific. However, other archs can still provide their own method, maybe a soc driver:

Documentation/ABI/testing/sysfs-devices-soc#n15



+static char *perf_pmu__getsysid(void)
+{
+ÂÂÂ char *sysid;
+ÂÂÂ static bool printed;
+
+ÂÂÂ sysid = getenv("PERF_SYSID");
+ÂÂÂ if (sysid)
+ÂÂÂÂÂÂÂ sysid = strdup(sysid);
+
+ÂÂÂ if (!sysid)
+ÂÂÂÂÂÂÂ sysid = get_sysid_str();
+ÂÂÂ if (!sysid)
+ÂÂÂÂÂÂÂ return NULL;
+
+ÂÂÂ if (!printed) {
+ÂÂÂÂÂÂÂ pr_debug("Using SYSID %s\n", sysid);
+ÂÂÂÂÂÂÂ printed = true;
+ÂÂÂ }
+ÂÂÂ return sysid;
+}

this part is getting complicated and AFAIK we have no tests for it

if you could think of any tests that'd be great.. Perhaps we could
load 'our' json test files and check appropriate events/aliasses
via in pmu object.. or via parse_events interface.. those test aliases
would have to be part of perf, but we have tests compiled in anyway

Sorry, I don't fully follow.

Are you suggesting that we could load the specific JSONs tables for a system
from the host filesystem?

I wish to see some test for all this.. I can only think about having
'test' json files compiled with perf and 'perf test' that looks them
up and checks that all is in the proper place

OK, let me consider this part for perf test support.

I will note that perf test has many issues on my arm64 board:

do] password for john:
1: vmlinux symtab matches kallsyms : Skip
2: Detect openat syscall event : FAILED!
3: Detect openat syscall event on all cpus : FAILED!
4: Read samples using the mmap interface : FAILED!
5: Test data source output : Ok
6: Parse event definition strings : FAILED!
7: Simple expression parser : Ok
8: PERF_RECORD_* events & perf_sample fields : Ok
9: Parse perf pmu format : Ok
10: DSO data read : Ok
11: DSO data cache : Ok
12: DSO data reopen : Ok
13: Roundtrip evsel->name : Ok
14: Parse sched tracepoints fields : FAILED!
15: syscalls:sys_enter_openat event fields : FAILED!
16: Setup struct perf_event_attr : Skip
17: Match and link multiple hists : Ok
18: 'import perf' in python : Ok
21: Breakpoint accounting : Ok
22: Watchpoint :
22.1: Read Only Watchpoint : Ok
22.2: Write Only Watchpoint : Ok
22.3: Read / Write Watchpoint : Ok
22.4: Modify Watchpoint : Ok
23: Number of exit events of a simple workload : Ok
24: Software clock events period values : Ok
25: Object code reading : Ok
26: Sample parsing : Ok
27: Use a dummy software event to keep tracking : Ok
28: Parse with no sample_id_all bit set : Ok
29: Filter hist entries : Ok
30: Lookup mmap thread : Ok
31: Share thread maps : Ok
32: Sort output of hist entries : Ok
33: Cumulate child hist entries : Ok
34: Track with sched_switch : Ok
35: Filter fds with revents mask in a fdarray : Ok
36: Add fd to a fdarray, making it autogrow : Ok
37: kmod_path__parse : Ok
38: Thread map : Ok
39: LLVM search and compile :
39.1: Basic BPF llvm compile : Skip
39.2: kbuild searching : Skip
39.3: Compile source for BPF prologue generation : Skip
39.4: Compile source for BPF relocation : Skip
40: Session topology : FAILED!
41: BPF filter :
41.1: Basic BPF filtering : Skip
41.2: BPF pinning : Skip
41.3: BPF prologue generation : Skip
41.4: BPF relocation checker : Skip
42: Synthesize thread map : Ok
43: Remove thread map : Ok
44: Synthesize cpu map : Ok
45: Synthesize stat config : Ok
46: Synthesize stat : Ok
47: Synthesize stat round : Ok
48: Synthesize attr update : Ok
49: Event times : Ok
50: Read backward ring buffer : FAILED!
51: Print cpu map : Ok
52: Merge cpu map : Ok
53: Probe SDT events : Ok
54: is_printable_array : Ok
55: Print bitmap : Ok
56: perf hooks umber__scnprintf : Ok
59: mem2node : Ok
60: time utils : Ok
61: Test jit_write_elf : Ok
62: maps__merge_in : Ok
63: DWARF unwind : Ok
64: Check open filename arg using perf trace + vfs_getname: FAILED!
65: Add vfs_getname probe to get syscall args filenames : FAILED!
66: Use vfs_getname probe to get syscall args filenames : FAILED!
67: Zstd perf.data compression/decompression : Ok
68: probe libc's inet_pton & backtrace it with ping : Skip
john@ubuntu:~/linux$

I know that the perf tool definitely has issues for system topology for arm64, which I need to check on.

Maybe I can conscribe help internally to help check the rest...

Thanks,
john