Re: [PATCH v3 17/20] perf symbol: Add memory shrinking for symbols, DSOs, and machines

[sashiko-bot@kernel.org]

> When profiling large workloads or systems with thousands of processes and
> shared libraries, perf can accumulate significant memory in loaded DSO
> symbol tables, secondary name-sorted symbol indices, cached DSO file data,
> and DWARF/addr2line state.
> 
> Because the lifetime of struct symbol is controlled by its owning
> struct dso, symbols in a referenced DSO (refcnt > 1) must remain valid for
> the lifetime of the DSO reference. However, auxiliary per-DSO allocations
> and unreferenced DSOs can still be reclaimed under memory pressure:
> 
> 1. symbols__shrink(): Reclaims the secondary name-sorted index
>    (symbols_by_name, which is rebuilt on demand by dso__sort_by_name())
>    and trims unused over-allocated tail capacity in the symbols array,
>    using down_write_trylock() so shrinking never deadlocks if invoked
>    while a symbol table lock is already held on the current stack.
> [ ... ]
>    shrink DSOs and evict unreferenced user DSOs (refcnt == 1, not kernel,
>    not vDSO, not hit, and not carrying header build-ids), followed by
>    malloc_trim(0) on glibc to return freed heap pages to the OS.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261110220803.2503416-1-irogers@google.com?part=17