From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D1AABC55174 for ; Wed, 5 Aug 2026 06:47:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: Content-Transfer-Encoding:Content-Type:In-Reply-To:References:To:From:Subject :MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=lzxl6ov54XABkEdqGVKNEiBDIIDgS5W3+aFuZLq5XxY=; b=KFstwXfoveUHit zXa0EhgMQAFIV0petkkXPSyJMKZgye7OcC8IY8gyXXTrs7H+8QAeei2gGjX2vITVWfYPvROJFBlpX 2OnSDbXnZwceBZ9JYjjb9CLP3zeUkKG8hM+QMjgEG9oAztDVOTza13pOVvogF6U19Mdt9wyTCKX3A 4t8DUwsCVEpVeNBC1Z+DVyZgAqClQ/YVphg8avPV0EVzOpU8ft1AERx23OLczfkRAcqgWdj8j2NK9 wbmqU/rvgzgk+dNuBl/gLbud71bcrA/bk8/msucJes5GDk0mmn1lU5Ho4LWNAc327J3zfPylBOX+U TEAoSA3E/N4SFOPkM/EA==; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: vladimir.murzin@arm.com, ryan.roberts@arm.com, peterz@infradead.org, catalin.marinas@arm.com, david.laight.linux@gmail.com, stable@vger.kernel.org, ruanjinjie@huawei.com, james.morse@arm.com, yang@os.amperecomputing.com, cl@gentwo.org, maz@kernel.org, ljs@kernel.org, will@kernel.org, ardb@kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 8/5/26 08:45, David Hildenbrand (Arm) wrote: >> Atop v7.2-rc4, with GCC 15.2.0 and defconfig, this is compiled as: >> >> | : >> | paciasp >> | stp x29, x30, [sp, #-16]! >> | mrs x2, sp_el0 >> | mov x29, sp >> | ldr w3, [x2, #8] >> | add w3, w3, #0x1 >> | str w3, [x2, #8] >> | mrs x3, tpidr_el1 >> | add x0, x0, x3 >> | 1: ldxr x5, [x0] >> | add x5, x5, x1 >> | stxr w4, x5, [x0] >> | cbnz w4, 1b >> | ldr x0, [x2, #8] >> | sub x0, x0, #0x1 >> | str w0, [x2, #8] >> | cbz x0, 2f >> | ldr x0, [x2, #8] >> | cbnz x0, 3f >> | 2: bl preempt_schedule_notrace >> | 3: ldp x29, x30, [sp], #16 >> | autiasp >> | ret > > FWIW, in a recent discussion on some prototype hacking [1] we saw some overhead > in micro-benchmarks that would really hammer on a path that would now do a > preempt_disable()+preempt_enable(). > > Switching from preempt_disable() to preempt_enable_no_resched() made it turn to > noise. Of course, that has other undesirable impacts, and I am not sure if we > are in the territory of code layout changes affecting the numbers. > > Just mentioning it as some data point. > [1] https://lore.kernel.org/linux-mm/20260630174852-mutt-send-email-mst@kernel.org/ -- Cheers, David