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 85DA21B0437; Tue, 12 Aug 2025 08:22:49 +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=1754986969; cv=none; b=YN9h2LGVJzDUY9DJ1hhm+DcziNwkQ89nBDqdODTRhxfQyQc1RCA5MdgDYbZLcNTqhoFtmg9Dgsn8hklngHNKxFTvoc5MMfko8aPIpcmUdaNLtrDC2Vsn8Q5sAQ3EDvOfv0p8wGEyra9mUj8GmJrI9a+Spm2504H4hSrWZFxdOxU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754986969; c=relaxed/simple; bh=SOEUCvkrPLt2cHYTej/oN0PrHTSMKACUoX3UK91QOnc=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=kuCIpx0No9hITnMQwsi7lGAvi70TTDCnW1mY5kuFC/qVLGFkjLHmW3r+upERxR6UmsdEBKLKdNCV2b/bNCHardTuQzCj89DsHsVWpsh9bZyJtcJ6QVxndSRSSfIYXFUB5LvCtWm7KBf1+ky+IiJo2bEVCmaPSFkGfXyezURud0Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DmuKztNS; 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="DmuKztNS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 61B7BC4CEF0; Tue, 12 Aug 2025 08:22:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754986969; bh=SOEUCvkrPLt2cHYTej/oN0PrHTSMKACUoX3UK91QOnc=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=DmuKztNSYXOf9162p+KgvmQJqJ7Lo2pii4ZU6f4YPV/QG3AgElpCsFbknaVQXDrgi jBXA/1r1k2vKNTTYj4RyHwDBMLN/FV68Xzr5p13a7pZtXFhvnJeYMhrSNPKJE3Vzyv DoxyxCPRfXoOIvpwrsjrHdytr2EFvVz07mqFe+K6FwvIadT5wxHkSnaPs9u4Cuc2GE 6mOcqTi4++iVqHu/KeNhZN3hOjqDdHIlle/vy8d+dbGc0+2YMpYGbJOVcECjAhFGg+ +P0C6dNHxCaP7gQu4C8VNM8Z2Z3U6pwurWGjnZUKTwguhA6pimV0t3vPVfrd17CzAj 5i2xWUqPfA1Eg== Message-ID: <16753b65-326d-48ba-90d2-476380455199@kernel.org> Date: Tue, 12 Aug 2025 16:22:45 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: chao@kernel.org, jaegeuk@kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org Subject: Re: [PATCH v3] f2fs: introduce flush_policy sysfs entry To: Christoph Hellwig References: <20250807034838.3829794-1-chao@kernel.org> Content-Language: en-US From: Chao Yu In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/12/25 15:59, Christoph Hellwig wrote: > On Tue, Aug 12, 2025 at 03:53:54PM +0800, Chao Yu wrote: >>> What did you use before? At least for older qemu the default was >>> buffered I/O, which can lead to very expensive fua or flush calls. >> >> Previously, I didn't use any cache= option, as manual described, it >> should equal to cache=wrteback. > > Modern qemu actually split the cache option. You absolute want > cache.direct=on. If you don't do simulated power fail testing by Yes, > killing qemu (or run real workloads for the matter, but who does that > :)) it might make sense to just ignore the flushes with cache.no-flush=on Yes, I don't care whether data can be persisted to host devices or not, nor killing qemu for test, so cache.no-flush=on looks good to me as well. > as well, which is what I do for my test VMs on the laptop. Thanks for sharing this, it helps. :) Thanks,