Re: [PATCH v2 3/3] perf unwind: Don't look up symbols when the caller doesn't want them

[sashiko-bot@kernel.org]

> Commit 02b2705017d2 ("perf callchain: Allow symbols to be optional when
> resolving a callchain") let callers that only need maps, such as
> build-id marking in 'perf record' and 'perf inject', resolve callchains
> without loading symbols. The DWARF unwinders were left out:
> thread__resolve_callchain_unwind() just notes that "Not resolving
> symbols with an unwinder isn't currently supported", and both libdw and
> libunwind look up the symbol of every frame they visit. The first lookup
> in a DSO loads its whole symbol table and demangles every name in it.
> 
> On arm64 this happens even for frame pointer callchains, because
> get_leaf_frame_caller_aarch64() runs a two frame DWARF unwind for every
> sample to recover the leaf function's caller. Since commit 29be60c93d2d
> ("perf build-id: Mark DSO in sample callchains"), process_buildids()
> does that for every sample at the end of 'perf record', so with -a it
> loads and demangles the symbol tables of every user binary sampled on
> [ ... ]
> and 15.5MB, with the same build-ids injected.
> 
> Fixes: 02b2705017d2 ("perf callchain: Allow symbols to be optional when resolving a callchain")
> Fixes: 29be60c93d2d ("perf build-id: Mark DSO in sample callchains")
> Signed-off-by: Matthew Wood <thepacketgeek@gmail.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261017000158.1178269-1-thepacketgeek@gmail.com?part=3