From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=74.125.82.71 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793142924; b=sjlDaq+t7t2TncVunUbDsPbTEB4k9y9AVuhuF5Gklf7bk6phmp7nOG181GHCU51qyWS1 wxLL6W/G3EMeRpBC2fIfh4Y3jOlNwXY5YPCk8D+uwm7zir7SMSpu4FRaRudxsWE+9fi1s 19y0Rv91A0h1QfxZEvRehFq6sqLRAEWvgmyo88bJtr0NYAFZIYlob3Yg5fgQ3QO0bALuN Ig3xLNvttkDb+zxCk8EZjejHay+wnGgwUVrDmVviJ9JZAHEJGNREQeCdPOKYqnZ/+JTEu BL4THg6FHvIdlzaeQYF2YD+cKJEfYg9og5fXk2NLae5m7AZk/y41HQazDTY2aGglI0w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793142924; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Received:Date:In-Reply-To: Mime-Version:References:X-Mailer:Message-ID:Subject:From:To:Cc: Content-Type; bh=ptu2Cc0GEGKDxeETDLH9JHqOyzOUYfVe0IfSZNyDWus=; b=gtzs+ldOCN76Vk3U2PS++wSG0shhScNdOOEkVYCMzaAI/pZPR9W/VxdFRZdnKxO2A2ti 4g5xE7fbYkkY9/HtJZ++C/DzImkuVTUZ0PzzOXUqbzOhP5UVScrBfIUzlKcU4TnQB98nP q0yHb5u8aTfmlGBsWFElGDeG4pWi2kcO4IHWknLthpkFIJQ0/0V88fnfSJlhXf8UGEgIW 23D5bGdOXh7VZvsNNVvoVfDAwXJyU4Z4lwZ7rWr288eoc+bLV0rASye1onPFZjIp/JX+y F4hRAtUwQWof4/5X7Mqt5X0XNkm9h3Y/CKPmUAC+FctfCNUC0zLKPrNikkllWhSkffQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=google.com; spf=pass smtp.mailfrom=flex--irogers.bounces.google.com; dkim=pass header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20260707 header.b=RVUwcXNs; arc=none smtp.remote-ip=74.125.82.71 Received: from mail-dl1-f71.google.com (mail-dl1-f71.google.com [74.125.82.71]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 50370606A321 for ; Tue, 27 Oct 2026 23:15:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 50370606A321 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--irogers.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20260707 header.b=RVUwcXNs Received: by mail-dl1-f71.google.com with SMTP id a92af1059eb24-1663fb7e005so430257c88.0 for ; Tue, 27 Oct 2026 16:15:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20260707; t=1793142923; x=1793747723; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=ptu2Cc0GEGKDxeETDLH9JHqOyzOUYfVe0IfSZNyDWus=; b=RVUwcXNs7H924w68dQT38SbZSO3JOPu9WBW3zdmWHaWY1IWOleF5CTEFW6OosIGgCT sCvFQ+PFTLMz+1XvXsbHzaTym8jit1IIW8fjEHXH7P445rehgiatYKM8zwUh6cvK+waw yYazaHImi09jxcCzG0KCJHF1QKc4SytVae5ANUsVUzjMFTd918W1wR91zaPC5sPfHJAJ iWF6iZntj9dxZeYDHYk2vLigq8urfn9ZYxQBQsTZUqmZxe8b4TED4c1EUDzbqsUeJ0kR zWDjxxXmPjR6CvOOtqjJ/L+fzLbDwhFaoaKv4gZKL+Y52SYwfqmVTGOEXOGIhKXOZVqB RApQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1793142923; x=1793747723; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=ptu2Cc0GEGKDxeETDLH9JHqOyzOUYfVe0IfSZNyDWus=; b=fiITbF1fXYLEeeuoWHxhXlXJOuHu5zu8eM6HeRPYWUarEgxUsU+zzbrm8qFvXa4iMy RvH7qcdgPxYzFRYJAOWtUg1P4AYJeka1yxIcODsfakW7+1M1iH90Pd4Yq3nlRtzHm0Z2 YO8ePsgK5ufS06bI6irMbeFyvIbDrtRBPbnJw38ou8MWJ2wutLR7/OWCS5ySlhIq4DQA ecGWBqCOPd9wNxpZMEjhlD7O66Rkle0dlj9Yki9WNYh9EvQQXjqYaDcR4Xppzclo1IfP jgZQOZ7WIkyD6nNazBjq2eLdzykvXK4U1XPXTnrZ1KB9uXyGs8+lQECKLsADrJAZ4FNb 3wBw== X-Forwarded-Encrypted: i=1; AKwUvByLRnWhQvoiO7qPI2HFXLtlckTSAFAYhZEX7vTPKYhP6e6YAnK7Ab8EeNYlKz13Tkk+6hhmiraijnqsbc4=@vger.kernel.org X-Gm-Message-State: AFq9FYIHHtWEeDWgIov88rZCK8PgkdRXp/a/Uni3PDRtLm/AuAzPXAE6 9bx8ISYuKNDKC1j/p3gF6e1TxD8Rda190TbOKUL/hTZaTJX86vf6pMBaALWWVwGelM/NqW/vT2j F75Np5p+bwA== X-Received: from dld12.prod.google.com ([2002:a05:7022:30c:b0:191:45cb:f8d3]) (user=irogers job=prod-delivery.src-stubby-dispatcher) by 2002:a05:7022:28c:b0:196:c1ca:3489 with SMTP id a92af1059eb24-1a6c2a861e2mr963707c88.0.1793142922918; Tue, 27 Oct 2026 16:15:22 -0700 (PDT) Date: Tue, 27 Oct 2026 16:14:56 -0700 In-Reply-To: <20261027231513.816148-1-irogers@google.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 References: <20260928075237.3055101-1-irogers@google.com> <20261027231513.816148-1-irogers@google.com> X-Mailer: git-send-email 2.56.0.313.g2479322e68-goog Message-ID: <20261027231513.816148-3-irogers@google.com> Subject: [PATCH v2 02/18] perf demangle: Add fast-path prefix checks for Rust and Java demanglers From: Ian Rogers To: irogers@google.com, acme@kernel.org, namhyung@kernel.org Cc: adrian.hunter@intel.com, haghdoost@uber.com, james.clark@linaro.org, jolsa@kernel.org, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, mingo@redhat.com, peterz@infradead.org Content-Type: text/plain; charset="UTF-8" During DSO symbol loading in dso__load_sym_internal(), dso__demangle_sym() is called for every ELF symbol. Both rust_demangle_demangle() and java_demangle_sym() previously performed string searches or buffer allocations before checking whether the symbol name could possibly be a mangled Rust or Java symbol, adding unnecessary overhead on plain C symbols. Add fast-path prefix checks in dso__demangle_sym() before calling rust_demangle_demangle() (using strstarts() for '_ZN', 'ZN', '__ZN', '_R', 'R', or '__R', keeping demangle-rust-v0.c unmodified relative to upstream rustc-demangle) and in java_demangle_sym() (requiring 'L', ';', '(', and ')') to reject non-Rust and non-Java symbol names immediately. Using 'perf bench internals symbols': Before (perf binary): Average DSO load + sort: 7.348 msec (+- 0.069 msec) After (perf binary, -4.2%): Average DSO load + sort: 7.041 msec (+- 0.051 msec) Before (libLLVM.so.21.1): Average DSO load + sort: 81.196 msec (+- 0.780 msec) After (libLLVM.so.21.1, -3.2%): Average DSO load + sort: 78.599 msec (+- 0.857 msec) Signed-off-by: Ian Rogers --- tools/perf/util/demangle-java.c | 23 +++++++++++++++++++++-- tools/perf/util/symbol.c | 15 ++++++++++++++- 2 files changed, 35 insertions(+), 3 deletions(-) diff --git a/tools/perf/util/demangle-java.c b/tools/perf/util/demangle-java.c index c3cb327ed562..5625c4de39eb 100644 --- a/tools/perf/util/demangle-java.c +++ b/tools/perf/util/demangle-java.c @@ -158,14 +158,33 @@ char * java_demangle_sym(const char *str, int flags) { char *buf, *ptr; - const char *p; + const char *l, *semi, *open, *p; size_t len, l1 = 0; if (!str) return NULL; + /* + * OpenJDK JIT symbols have the form: + * [prefix]L;() + * where the return type (such as 'I' for int or 'V' for void) is at the + * end after ')'. In __demangle_java_sym(), the parser starts in + * MODE_PREFIX and only reaches MODE_TYPE (required when ')' is reached) + * via 'L' (MODE_CLASS) -> ';' (MODE_FUNC) -> '(' (MODE_TYPE). Verify + * those delimiters appear in order before allocating the output buffer. + */ + l = strchr(str, 'L'); + if (!l) + return NULL; + semi = strchr(l + 1, ';'); + if (!semi) + return NULL; + open = strchr(semi + 1, '('); + if (!open) + return NULL; + /* find start of return type */ - p = strrchr(str, ')'); + p = strrchr(open + 1, ')'); if (!p) return NULL; diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c index b61a574ce9a3..dc70bbe8514f 100644 --- a/tools/perf/util/symbol.c +++ b/tools/perf/util/symbol.c @@ -2738,7 +2738,20 @@ char *dso__demangle_sym(struct dso *dso, int kmodule, const char *elf_name) if (!want_demangle((dso && dso__kernel(dso)) || kmodule)) return demangled; - rust_demangle_demangle(elf_name, &rust_demangle); + /* + * Rust mangled symbols start with one of the prefixes checked by + * rust_demangle_legacy_demangle() ("_ZN", Windows dbghelp "ZN", or + * macOS "__ZN") or rust_demangle_v0_demangle() ("_R", Windows dbghelp + * "R", or macOS "__R") in demangle-rust-v0.c. Check the prefix here so + * we avoid calling rust_demangle_demangle() (which scans the entire + * symbol name with strstr() and strlen() for ThinLTO ".llvm." suffixes) + * on non-Rust symbols, while keeping demangle-rust-v0.c unmodified + * relative to upstream rustc-demangle. + */ + if (strstarts(elf_name, "_ZN") || strstarts(elf_name, "ZN") || + strstarts(elf_name, "__ZN") || strstarts(elf_name, "_R") || + strstarts(elf_name, "R") || strstarts(elf_name, "__R")) + rust_demangle_demangle(elf_name, &rust_demangle); if (rust_demangle_is_known(&rust_demangle)) { /* A rust mangled name. */ if (rust_demangle.mangled_len == 0) -- 2.56.0.313.g2479322e68-goog