From: Serhei Makarov <serhei@serhei.io>
To: irogers@google.com
Cc: acme@kernel.org, aditya.b1@linux.ibm.com,
adrian.hunter@intel.com, ak@linux.intel.com, alex@ghiti.fr,
aou@eecs.berkeley.edu, atrajeev@linux.ibm.com, ctshao@google.com,
dvyukov@google.com, guoren@kernel.org, haibo1.xu@intel.com,
howardchu95@gmail.com, james.clark@linaro.org,
john.g.garry@oracle.com, jolsa@kernel.org,
krzysztof.m.lopatowski@gmail.com, leo.yan@linux.dev,
linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
linux-riscv@lists.infradead.org, linux@treblig.org,
mark@klomp.org, mingo@redhat.com, namhyung@kernel.org,
palmer@dabbelt.com, peterz@infradead.org, pjw@kernel.org,
shimin.guo@skydio.com, slyich@gmail.com,
stephen.s.brennan@oracle.com, thomas.falcon@intel.com,
will@kernel.org
Subject: Re: [PATCH v1 22/23] perf unwind-libdw: Don't discard loaded ELF/Dwarf after every unwind
Date: Tue, 27 Jan 2026 12:42:53 -0500 [thread overview]
Message-ID: <20260127174253.396766-1-serhei@serhei.io> (raw)
In-Reply-To: <20260117052849.2205545-23-irogers@google.com>
> As removing the dwfl didn't prove possible, an alternative is to just not discard the dwfl when the unwind ends. The dwfl is valid for a process unless a dso is loaded at the same address as a previous one. So keep the dwfl with the maps, invalidate it if a map is removed (in case a new map replaces it) and recycle the dwfl in the unwinding code.
Relevant note:
I'm looking at whether elfutils libdwfl_stacktrace might further help with these issues. The libdwfl_stacktrace library is currently shipped as an experimental addon to libdwfl in elfutils 0.194, but I'm intending to stabilize the API this year. There's code for some analogous functions: translating perf->dwarf register files, and caching Dwfl and Elf data to speed up unwinding across multiple processes. (Thus, if unwinding a collection of perf_events from 16 processes that use libc, we don't need to load the CFI for libc.so 16 times.)
I think once I've stabilized the libdwfl_stacktrace API and expanded the register support to a larger set of perf-supported architectures, it makes sense for me to author a corresponding set of patches for perf. I'll see if it's worth adding more libdwflst functionality to elfutils 0.195 in anticipation of this.
-- Serhei Makarov
next prev parent reply other threads:[~2026-01-27 17:43 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-17 5:28 [PATCH v1 00/23] perf dwarf/libdw extra support, speed and clean ups Ian Rogers
2026-01-17 5:28 ` [PATCH v1 01/23] perf symbol-elf: Fix leak of ELF files with GNU debugdata Ian Rogers
2026-01-17 5:28 ` [PATCH v1 02/23] perf dso: Extra validity checks that e_machine is valid Ian Rogers
2026-01-17 5:28 ` [PATCH v1 03/23] perf record: Disable inline frames when marking build IDs Ian Rogers
2026-01-17 5:28 ` [PATCH v1 04/23] perf unwind-libdw: fix a cross-arch unwinding bug Ian Rogers
2026-01-20 16:02 ` Arnaldo Carvalho de Melo
2026-01-20 17:53 ` Ian Rogers
2026-01-17 5:28 ` [PATCH v1 05/23] perf libdw_addr2line: Fixes to srcline memory allocation Ian Rogers
2026-01-17 5:28 ` [PATCH v1 06/23] perf unwind-libdw: Correct argument to dwfl_attach_state Ian Rogers
2026-01-17 5:28 ` [PATCH v1 07/23] perf powerpc: Unify the skip-callchain-idx libdw with that for addr2line Ian Rogers
2026-01-17 5:28 ` [PATCH v1 08/23] perf perf_regs: Switch from arch string to int e_machine Ian Rogers
2026-01-20 18:49 ` Arnaldo Carvalho de Melo
2026-01-21 6:58 ` Mi, Dapeng
2026-01-21 7:10 ` Ian Rogers
2026-01-17 5:28 ` [PATCH v1 09/23] perf dwarf-regs: Add util/dwarf-regs-arch for consistency with perf-regs Ian Rogers
2026-01-17 5:28 ` [PATCH v1 10/23] perf dwarf-regs: Remove get_arch_regnum Ian Rogers
2026-01-17 5:28 ` [PATCH v1 11/23] perf dwarf-regs: Clean up x86 dwarf_regnum code Ian Rogers
2026-01-17 5:28 ` [PATCH v1 12/23] perf dwarf-regs: Add get_dwarf_regnum_for_perf_regnum and use for x86 unwinding Ian Rogers
2026-01-17 5:42 ` Ian Rogers
2026-01-17 5:28 ` [PATCH v1 13/23] perf dwarf-regs: Add basic get_dwarf_regnum for most architectures Ian Rogers
2026-01-17 5:28 ` [PATCH v1 14/23] perf dwarf-regs: Add ARM perf to dwarf register number mapping functions Ian Rogers
2026-01-17 5:28 ` [PATCH v1 15/23] perf dwarf-regs: Add csky " Ian Rogers
2026-01-17 5:28 ` [PATCH v1 16/23] perf dwarf-regs: Add loongarch " Ian Rogers
2026-01-17 5:28 ` [PATCH v1 17/23] perf dwarf-regs: Add powerpc " Ian Rogers
2026-01-17 5:28 ` [PATCH v1 18/23] perf dwarf-regs: Add RISC-V " Ian Rogers
2026-01-17 5:28 ` [PATCH v1 19/23] perf dwarf-regs: Add S390 " Ian Rogers
2026-01-17 5:28 ` [PATCH v1 20/23] perf dwarf-regs: Add MIPS " Ian Rogers
2026-01-17 5:28 ` [PATCH v1 21/23] perf build: Remove NO_LIBDW_DWARF_UNWIND option Ian Rogers
2026-01-17 5:28 ` [PATCH v1 22/23] perf unwind-libdw: Don't discard loaded ELF/Dwarf after every unwind Ian Rogers
2026-01-27 17:42 ` Serhei Makarov [this message]
2026-01-27 18:08 ` Ian Rogers
2026-01-17 5:28 ` [PATCH v1 23/23] perf machine: Add inline information to frame pointer and LBR callchains Ian Rogers
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