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 4087D1C5D5E
	for <linux-kernel@vger.kernel.org>; Thu, 29 Jan 2026 23:53:15 +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=1769730796; cv=none; b=KJAaZhy5vNsqr2JZw+Lh/yl/Uzw26wpemSGU0WfE8+Gs9tdhYpNfvaEVGMFgVxsABp6ug60q1DqhmzS4WLzAsUrv6zfzMJ+O4EOsjGNHjmsYANaGWE+J86aAExVEDU4nf3D03RuC/gBOQ6BvkLag8XID1mOxXITs71xpDxLEak4=
ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org;
	s=arc-20240116; t=1769730796; c=relaxed/simple;
	bh=0TKcMYGC45Pj1NeFS56tIOTMpJjenlLeDK6o7cBLWN4=;
	h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References:
	 Mime-Version:Content-Type; b=iu6h4RhNeXb8cu0L8zObmysphlhy+JR3dFhzjSE68p+2Wf5gt5VCaiiUtWGuRWLQvyaF1lOE1sPRVFWKyvuKKa5zLNtXSOHQqqMc+b1E3WWdthLVco9w8WKb7T9wE9PS22BGiie4H+K1xHGUUUx5zt/bsXiVYPr8nqMcZlZtfPA=
ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=sHgzK8Jy; arc=none smtp.client-ip=10.30.226.201
Authentication-Results: smtp.subspace.kernel.org;
	dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="sHgzK8Jy"
Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9D340C4CEF7;
	Thu, 29 Jan 2026 23:53:15 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org;
	s=korg; t=1769730795;
	bh=0TKcMYGC45Pj1NeFS56tIOTMpJjenlLeDK6o7cBLWN4=;
	h=Date:From:To:Cc:Subject:In-Reply-To:References:From;
	b=sHgzK8Jy5P/vp1xZG17+OtWZvp6VWWQQYglM0ALWanRFtHAXV8vMd0XUa+Q7uJFak
	 WXZZDa9j1P9WfkQfP5YW0LrX3EH+VMEvtzTQoCIkfrt9ZdZrCJeMGQMp46rA9U96jT
	 66KKWAyQMWtPi4qK+glS8ClBLQHYKTqm4B70jTgA=
Date: Thu, 29 Jan 2026 15:53:15 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Matteo Croce <technoboy85@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KUnit: memcpy: add benchmark
Message-Id: <20260129155315.5897a90efedbc6988ebb3708@linux-foundation.org>
In-Reply-To: <CAFnufp3Ce-ssx4143_+zc4HWPMx4Rn9kAsVwoK=tqBfSXG0-qQ@mail.gmail.com>
References: <20260129004328.102770-1-teknoraver@meta.com>
	<20260129152035.1fbdddb214c75875b67ba5b9@linux-foundation.org>
	<CAFnufp3Ce-ssx4143_+zc4HWPMx4Rn9kAsVwoK=tqBfSXG0-qQ@mail.gmail.com>
X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu)
Precedence: bulk
X-Mailing-List: linux-kernel@vger.kernel.org
List-Id: <linux-kernel.vger.kernel.org>
List-Subscribe: <mailto:linux-kernel+subscribe@vger.kernel.org>
List-Unsubscribe: <mailto:linux-kernel+unsubscribe@vger.kernel.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit

On Fri, 30 Jan 2026 00:36:30 +0100 Matteo Croce <technoboy85@gmail.com> wrote:

> > Is cond_resched() inside preempt_disable() actually legal?
> >
> > Might be, but it doesn't make a lot of sense, does it?
> >
> > > +     }
> > > +     preempt_enable();
> > > +
> >
> 
> Right. In a previous version I was doing
> preempt_disable()/preempt_enable() around the two ktime_get_ns(), but
> then I thought that enabling and disabling preemption 100 time was too
> much.
> I'll restore the preempt macros around the actual copy and remove
> cond_resched().

OK.

local_irq_save() would be more accurate.  

Does it really need to copy 4MB?  Smaller would make
local_irq_disable() more viable.

kmalloc(4MB) does seem to be pushing our luck.  I'm spotting

	./arch/arm/configs/pxa_defconfig:CONFIG_ARCH_FORCE_MAX_ORDER=8

which is 1MB?