linux-kernel - [PATCH 21/22] objtool: Free insns when done

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Message-Id: <4d4bca1a0f869de020dac80d91f9acbf6df77eab.1685464332.git.jpoimboe@kernel.org>
Date:   Tue, 30 May 2023 10:21:13 -0700
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Miroslav Benes <mbenes@...e.cz>
Subject: [PATCH 21/22] objtool: Free insns when done

Free the decoded instructions as they're no longer needed after this
point.  This frees up a big chunk of heap, which will come handy when
skipping the reading of DWARF section data.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 tools/objtool/check.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 65c59b0b1e96..80d3a97e442b 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4587,6 +4587,34 @@ static int disas_warned_funcs(struct objtool_file *file)
 	return 0;
 }
 
+struct insn_chunk {
+	void *addr;
+	struct insn_chunk *next;
+};
+
+/*
+ * Reduce peak RSS usage by freeing insns memory before writing the ELF file,
+ * which can trigger more allocations for .debug_* sections whose data hasn't
+ * been read yet.
+ */
+static void free_insns(struct objtool_file *file)
+{
+	struct instruction *insn;
+	struct insn_chunk *chunks = NULL, *chunk;
+
+	for_each_insn(file, insn) {
+		if (!insn->idx) {
+			chunk = malloc(sizeof(*chunk));
+			chunk->addr = insn;
+			chunk->next = chunks;
+			chunks = chunk;
+		}
+	}
+
+	for (chunk = chunks; chunk; chunk = chunk->next)
+		free(chunk->addr);
+}
+
 int check(struct objtool_file *file)
 {
 	int ret, warnings = 0;
@@ -4731,6 +4759,8 @@ int check(struct objtool_file *file)
 		warnings += ret;
 	}
 
+	free_insns(file);
+
 	if (opts.verbose)
 		disas_warned_funcs(file);
 
-- 
2.40.1