Messages in this thread | | | Subject | Re: [PATCH v5] perf record: collect user registers set jointly with dwarf stacks | From | Alexey Budankov <> | Date | Fri, 31 May 2019 09:27:38 +0300 |
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On 30.05.2019 22:41, Arnaldo Carvalho de Melo wrote: > Em Thu, May 30, 2019 at 10:03:36PM +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 >> captured on a sample: >> >> $ perf record -g --call-graph dwarf,1024 --user-regs=IP,SP,BP -- stack_test2.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. IP and SP registers (DWARF_MINIMAL_REGS) >> are collected anyways regardless of the --user-regs value provided from >> the command line: > > Applied, changed the subject and description to: > > perf record: Allow mixing --user-regs with --call-graph=dwarf > > When DWARF stacks were requested and at the same time that the user > specifies a register set using the --user-regs option the full register > context was being captured on samples: > > $ perf record -g --call-graph dwarf,1024 --user-regs=IP,SP,BP -- stack_test2.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 > > I.e. the --user-regs=IP,SP,BP was being ignored, being overridden by the > needs of --call-graph=dwarf. > > After applying the change in this patch the sample data contains the > user specified register, but making sure that at least the minimal set > of register needed for DWARF unwinding (DWARF_MINIMAL_REGS) is > requested. > > The user is warned that DWARF unwinding may not work if extra registers > end up being needed. > > -g call-graph dwarf,K full_regs > --user-regs=user_regs user_regs > -g call-graph dwarf,K --user-regs=user_regs user_regs + DWARF_MINIMAL_REGS > <REST remains the same> >
Sounds better. Thanks!
~Alexey
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