From nobody Fri Nov 22 22:25:35 2024 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 64A561D618A for ; Fri, 15 Nov 2024 17:20:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731691248; cv=none; b=aKIknrx/bp7TB+yD5ZLjQbarsOerxVCIoBjd5SJ+RJUc0UuRTpG61eiXEAc5YvYCWuvtV2JrCIStEv8cvu11rT8luENyW6t1BUVDBN1KHI81tXGnKj3wZu+lB8E4XovIY9kV4nEz1ulPKsMpAE5YhdnCnu56S0EqleEnpMNhrzg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731691248; c=relaxed/simple; bh=DH58qurgKZ3NE3npPwHdlb4AJ1ljYjCmbxGxiwkUg2w=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iIRK4JT32z1uqG/jRG+NXNsyVJFaLDQ6MyEeCpPI3tYIYue6SiafbFDolcVGvdIYyO/lqDZ8x0GAbRWOah+XhZzMqak+ttcXbhE/eCjZd5LizQc1p4yhopU9KJ4oj3hqgO4BaukBWBXerQuhmqg1qDz/lV8XZlL2+X/2cflKmIg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=DUu2icoD; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=albHp5bJ; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="DUu2icoD"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="albHp5bJ" From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1731691243; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=UuNDl7xyS9sedFEMEU6wMQC/X2A0lAOMTqby/qP6gQU=; b=DUu2icoDMQXb1lm7Uf83Udw4o+I1YgUvz2s+EZ0Ztq5zyzrRgpzRxMoxTQ0hNMYw+EBfuH gyz7HCmwjIOyBsOUPNg28x856AxW+BsjlcXeqnQrmy7iWHKVxGceqGQ/OXZvHmTuXBPGat Iaa5E5dAD+OzeVSrPOxKwCBja/YPhf2UkrplHrWyu89UQhsojB1ISCgCVtRhEG/xgvk3tn StHVexJHG5EQvSmosAxH9Phzz0DOplCfFgsi7QR9U5swWiEc8FsbqHOliaHQAZT0TE5IOn PO/p3bCMyq6sbCnbFn0tl/dJRwAU3SYHGZ73lzoVB6ktPLXrDUGRnW3NF2XC9Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1731691243; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=UuNDl7xyS9sedFEMEU6wMQC/X2A0lAOMTqby/qP6gQU=; b=albHp5bJu0xft0J9jVLygTXTFxxh/thCXImsz4FJILcjgsZSUZSlbT0UYUEJzPr+Kqx+sP pVCILychx9bHzPCA== To: linux-kernel@vger.kernel.org Cc: =?UTF-8?q?Andr=C3=A9=20Almeida?= , Darren Hart , Davidlohr Bueso , Ingo Molnar , Juri Lelli , Peter Zijlstra , Thomas Gleixner , Valentin Schneider , Waiman Long , Sebastian Andrzej Siewior Subject: [RFC PATCH v3 4/9] futex: Hash only the address for private futexes. Date: Fri, 15 Nov 2024 17:58:45 +0100 Message-ID: <20241115172035.795842-5-bigeasy@linutronix.de> In-Reply-To: <20241115172035.795842-1-bigeasy@linutronix.de> References: <20241115172035.795842-1-bigeasy@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" futex_hash() passes the whole futex_key to jhash2. The first two member are passed as the first argument and the offset as the "initial value". For private futexes, the mm-part is always the same and it is used only within the process. By excluding the mm part from the hash, we reduce the length passed to jhash2 from 4 (16 / 4) to 2 (8 / 2). This avoids the __jhash_mix() part of jhash. The resulting code is smaller and based on testing this variant performs as good as the original or slightly better. Signed-off-by: Sebastian Andrzej Siewior --- kernel/futex/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/futex/core.c b/kernel/futex/core.c index 2f5087fde57ef..5b66b6e52aeb5 100644 --- a/kernel/futex/core.c +++ b/kernel/futex/core.c @@ -134,8 +134,8 @@ struct futex_hash_bucket *futex_hash(union futex_key *k= ey) if (fhb && futex_key_is_private(key)) { u32 hash_mask =3D current->mm->futex_hash_mask; =20 - hash =3D jhash2((u32 *)key, - offsetof(typeof(*key), both.offset) / 4, + hash =3D jhash2((void *)&key->private.address, + sizeof(key->private.address) / 4, key->both.offset); return &fhb[hash & hash_mask]; } --=20 2.45.2