Bug#767756: glibc: Consider providing a libc build compiled with -fno-omit-frame-pointer to help with profiling
On Sun, Feb 16, 2020, at 14:15, Florian Weimer wrote: > Most unwinders should be able to use asynchronous unwind tables, which > only impact disk size (and the size of VM mappings). Experience with perf shows orders of magnitude of overhead of DWARF unwinding over fp based unwinding. The kernel uses ORC for this reason, which is up to 20-40x faster than DWARF, in addition to the removal of the 5-10% DWARF performance penalty caused by .text size increase. It is however not available for user-space programs. Since it uses ORC, DWARF unwinding is also unavailable in (and unlikely to be ever supported by) the kernel, including the bpf_get_stack* helpers used in eBPF. Since most interaction with the kernel is done through libc, this unfortunately makes it impossible to meaningfully inspect user-space programs in response to events, which is one of the biggest selling points of bpf tracing.
Processed: Bug#951237 marked as pending in glibc
Processing control commands: > tag -1 pending Bug #951237 [src:glibc] glibc/mips: bpo patch: mips: Fix argument passing for inlined syscalls on Linux [BZ #25523] Ignoring request to alter tags of bug #951237 to the same tags previously set -- 951237: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=951237 Debian Bug Tracking System Contact ow...@bugs.debian.org with problems
Processed: Bug#951237 marked as pending in glibc
Processing control commands: > tag -1 pending Bug #951237 [src:glibc] glibc/mips: bpo patch: mips: Fix argument passing for inlined syscalls on Linux [BZ #25523] Added tag(s) pending. -- 951237: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=951237 Debian Bug Tracking System Contact ow...@bugs.debian.org with problems
Bug#767756: glibc: Consider providing a libc build compiled with -fno-omit-frame-pointer to help with profiling
* Aurelien Jarno: >> I've been running into this myself a lot lately and wonder if >> anything has happened regarding this since 2014, after all it's >> been six years. >> I'm surprised so few people seem to be taking interest in this >> considering the amount of tools that rely on frame pointers for >> performant stack traces, which has further increased with the >> introduction of eBPF. > > I understand the need for -fno-omit-frame-pointer, however it has a > performance impact, so we do not want to do that by default. OTOH > providing an alternative libc is something tricky if we do not want it > to do it without breaking systems. Someone has to come with a patch that > is well tested. Most unwinders should be able to use asynchronous unwind tables, which only impact disk size (and the size of VM mappings).
Bug#767756: glibc: Consider providing a libc build compiled with -fno-omit-frame-pointer to help with profiling
Hi, On 2020-02-16 03:32, notafile wrote: > Hi, > > I've been running into this myself a lot lately and wonder if anything has > happened regarding this since 2014, after all it's been six years. > I'm surprised so few people seem to be taking interest in this considering > the amount of tools that rely on frame pointers for performant stack traces, > which has further increased with the introduction of eBPF. I understand the need for -fno-omit-frame-pointer, however it has a performance impact, so we do not want to do that by default. OTOH providing an alternative libc is something tricky if we do not want it to do it without breaking systems. Someone has to come with a patch that is well tested. Aurelien -- Aurelien Jarno GPG: 4096R/1DDD8C9B aurel...@aurel32.net http://www.aurel32.net
