From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 2016E38551E; Mon, 9 Mar 2026 09:53:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773049982; cv=none; b=WLdQlVpTkdjQGqx9wRR4thLjlPupiGgfG8hPZxPpopv+zuJXHI1QusQBCB1okbvJsVqWGa/QLivyMH4zgHAD+eT3IIINErx3w8pBb28n9GKU3KKv+7DTft7Inu4Qa5K34Iivz+fjRkQWcPhBlzoGi3IQCqx+hc3+Q28voJz89cs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773049982; c=relaxed/simple; bh=PMIuKPsEvPXOB7oPgsM4Nr0xqxaEsQcqjc5S8SS+m8Q=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=sQ4x08bwWNHl1jGw6iXkfgLsMtYwKXI6lSYOPHY00+BmC9WPTNXnrn08H4eoU890Yr9eri7UdIvMl8f5eVPmBRRMqYAJlV4KXFuMYoHFSzJsJbw42Prp+AugksuGXjcfC8jxw9VfVciXurBsyUvm9k6RfqrDz1TeGq5cUOm2GC8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WmiafaaU; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="WmiafaaU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 54B89C4CEF7; Mon, 9 Mar 2026 09:52:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773049981; bh=PMIuKPsEvPXOB7oPgsM4Nr0xqxaEsQcqjc5S8SS+m8Q=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=WmiafaaUd3N0urhZWm8ej60bzApAWQpt38JX2BoGr8OV3tszUuCJojKJMQmYGdJ7W V9ZbwFBsf3RvRRBvf64aM99RzGfnI6VWkyivf4ZCXOhHJrOyJT1wo6kpxeMJIK0Pmw O7H3J/IumMBFvtMEh5bfxgrIpVQ0tPc7ggQzTNSnbh3/hzml5wwraMlQ7GFkUt6CMo vPXRZ+fzEvf6PqDOraPeM+pWGxu0R/MO6kMV39rYN6HkXH3aaB5DTR8LjuqgabY7jh cP8GCa9K2RzX+qioulCI1ELzbTJD/VWY0bFe5y0mj7qmsdOijRN+Sp8gAcUgJDz4IT NWvu6F0HYsBaQ== Message-ID: Date: Mon, 9 Mar 2026 10:52:55 +0100 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/4] Introduce QPW for per-cpu operations To: Leonardo Bras , Marcelo Tosatti Cc: Michal Hocko , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Leonardo Bras , Thomas Gleixner , Waiman Long , Boqun Feng , Frederic Weisbecker References: <20260206143430.021026873@redhat.com> From: "Vlastimil Babka (SUSE)" Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/8/26 18:41, Leonardo Bras wrote: > Hi Marcelo, > > Great, hiding migrate_disable under the static branch is the best scenario. > > I wonder why we spend 2 cycles on the static branches, though, should be > close to nothing unless the branch predictor is too busy already. Well, we AFAIK static branches are runtime patched to non-conditional jumps or nops, so there's nothing left for the branch predictor to do. Or maybe I misunderstand your comment. It does however increase code footprint and thus instruction cache usage, so maybe that's an effect of that. > can always try to optimize in a different way. > > Thanks for the effort on this! > Leo