linux-kernel - [tip: objtool/core] objtool: Use sec_offset_hash() for insn

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Date:   Wed, 22 Apr 2020 22:24:31 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: objtool/core] objtool: Use sec_offset_hash() for insn_hash

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     e499ccee47c429be75dee8a94d8f289aa133e3a0
Gitweb:        https://git.kernel.org/tip/e499ccee47c429be75dee8a94d8f289aa133e3a0
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Mon, 16 Mar 2020 15:47:27 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 22 Apr 2020 23:10:07 +02:00

objtool: Use sec_offset_hash() for insn_hash

In preparation for find_insn_containing(), change insn_hash to use
sec_offset_hash().

This actually reduces runtime; probably because mixing in the section
index reduces the collisions due to text sections all starting their
instructions at offset 0.

Runtime on vmlinux.o from 3.1 to 2.5 seconds.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Miroslav Benes <mbenes@...e.cz>
Reviewed-by: Alexandre Chartre <alexandre.chartre@...cle.com>
Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
Link: https://lkml.kernel.org/r/20200416115119.227240432@infradead.org
---
 tools/objtool/check.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 39d1d4f..584f221 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -34,9 +34,10 @@ struct instruction *find_insn(struct objtool_file *file,
 {
 	struct instruction *insn;
 
-	hash_for_each_possible(file->insn_hash, insn, hash, offset)
+	hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
 		if (insn->sec == sec && insn->offset == offset)
 			return insn;
+	}
 
 	return NULL;
 }
@@ -282,7 +283,7 @@ static int decode_instructions(struct objtool_file *file)
 			if (ret)
 				goto err;
 
-			hash_add(file->insn_hash, &insn->hash, insn->offset);
+			hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
 			list_add_tail(&insn->list, &file->insn_list);
 			nr_insns++;
 		}