On 13.05.2019 22:43, Arnaldo Carvalho de Melo wrote: > Em Mon, Apr 22, 2019 at 05:37:52PM +0300, Alexey Budankov escreveu: >> >> When dwarf stacks are collected jointly with user specified register >> set using --user-regs option like below the full register context is >> still captured on a sample: >> >> $ perf record -g --call-graph dwarf,1024 --user-regs=IP,SP,BP -- >> matrix.gcc.g.O3 >> >> 188143843893585 0x6b48 [0x4f8]: PERF_RECORD_SAMPLE(IP, 0x4002): >> 23828/23828: 0x401236 period: 1363819 addr: 0x7ffedbdd51ac >> ... FP chain: nr:0 >> ... user regs: mask 0xff0fff ABI 64-bit >> .... AX 0x53b >> .... BX 0x7ffedbdd3cc0 >> .... CX 0xffffffff >> .... DX 0x33d3a >> .... SI 0x7f09b74c38d0 >> .... DI 0x0 >> .... BP 0x401260 >> .... SP 0x7ffedbdd3cc0 >> .... IP 0x401236 >> .... FLAGS 0x20a >> .... CS 0x33 >> .... SS 0x2b >> .... R8 0x7f09b74c3800 >> .... R9 0x7f09b74c2da0 >> .... R10 0xfffffffffffff3ce >> .... R11 0x246 >> .... R12 0x401070 >> .... R13 0x7ffedbdd5db0 >> .... R14 0x0 >> .... R15 0x0 >> ... ustack: size 1024, offset 0xe0 >> . data_src: 0x5080021 >> ... thread: stack_test2.g.O:23828 >> ...... dso: /root/abudanko/stacks/stack_test2.g.O3 >> >> After applying the change suggested in the patch the sample data contain >> only user specified register values: >> >> $ perf record -g --call-graph dwarf,1024 --user-regs=BP -- matrix.gcc.g.03 >> >> 188368474305373 0x5e40 [0x470]: PERF_RECORD_SAMPLE(IP, 0x4002): >> 23839/23839: 0x401236 period: 1260507 addr: 0x7ffd3d85e96c >> ... FP chain: nr:0 >> ... user regs: mask 0x1c0 ABI 64-bit >> .... BP 0x401260 >> .... SP 0x7ffd3d85cc20 >> .... IP 0x401236 >> ... ustack: size 1024, offset 0x58 >> . data_src: 0x5080021 >> ... thread: stack_test2.g.O:23839 >> ...... dso: /root/abudanko/stacks/stack_test2.g.O3 >> >> IP and SP registers (dwarf_regs) are collected anayways regardless of >> the --user-regs option value provided from the command line: > > So user asks for a, b and c and gets a, b, c + d and e? At the very > least we should warn that those registers are being added to the mix, > i.e. something like: > > WARNING: specified --user-regs register set doesn't include registers > needed by also specified --call-graph=dwarf, auto adding missing > registers (list of missing registers auto-added).
Well, let's have it like this. ~Alexey > > - Arnaldo > > P.S. Back from vacation, going thru backlog, hopefully will apply your > perf.data compression patchkit after testing its patches one by one, > sorry for the delay for that one (and this :)) > >> -g call-graph dwarf,K full_regs >> -g call-graph dwarf,K --user-regs=user_regs user_regs | dwarf_regs >> --user-regs=user_regs user_regs >> >> Signed-off-by: Alexey Budankov <[email protected]> >> --- >> Changes in v3: >> - avoid changes in platform specific header files >> >> Changes in v2: >> - implemented dwarf register set to avoid corrupted trace >> when --user-regs option value omits IP,SP >> >> --- >> tools/perf/util/evsel.c | 8 +++++++- >> 1 file changed, 7 insertions(+), 1 deletion(-) >> >> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c >> index 84cfb9fe2fc6..e5e61ee3c6e7 100644 >> --- a/tools/perf/util/evsel.c >> +++ b/tools/perf/util/evsel.c >> @@ -669,6 +669,9 @@ int perf_evsel__group_desc(struct perf_evsel *evsel, >> char *buf, size_t size) >> return ret; >> } >> >> +#define DWARF_REGS_MASK ((1ULL << PERF_REG_IP) | \ >> + (1ULL << PERF_REG_SP)) >> + >> static void __perf_evsel__config_callchain(struct perf_evsel *evsel, >> struct record_opts *opts, >> struct callchain_param *param) >> @@ -702,7 +705,10 @@ static void __perf_evsel__config_callchain(struct >> perf_evsel *evsel, >> if (!function) { >> perf_evsel__set_sample_bit(evsel, REGS_USER); >> perf_evsel__set_sample_bit(evsel, STACK_USER); >> - attr->sample_regs_user |= PERF_REGS_MASK; >> + if (opts->sample_user_regs) >> + attr->sample_regs_user |= DWARF_REGS_MASK; >> + else >> + attr->sample_regs_user |= PERF_REGS_MASK; >> attr->sample_stack_user = param->dump_size; >> attr->exclude_callchain_user = 1; >> } else { >> -- >> 2.20.1 >
