From mboxrd@z Thu Jan 1 00:00:00 1970 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.subspace.kernel.org (Postfix) with ESMTPS id 638761D86F2; Wed, 12 Mar 2025 06:24:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741760649; cv=none; b=OK0H1OkXU7f81OpbfvYem7oMXEnrX1ZRtRnxpdQApzjikBX1alOSzntuNZ9IsnW1T87lgVBDPNABpJKyC0ONHYWRf26DOHJ59se2zOqqhM0hB1C5WLCrinJrSVuaF8iCvzD1MfCaS7pA5HXVo/P6tQ/cnLai6f6udPwuf24NQgI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741760649; c=relaxed/simple; bh=v0gdL/3I1B1zmaBLpSypGmJbmVvLAJ0k7+jEv5AuK60=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=FyeKYLRDCIUVFkAVtRWeWEYst5lB4RUe0+IgIE3dKpNUXhoghFcWRw3DEIcdyHn3+kZlT//YG42khu1jXSuzJ8L/yGzFGIqwwlDqQuFvZfFAUMZVdUiLFNopp8QWcSPYnLVhCoG5fiRehvkJC0wfpsJlyIgzgnaOEknuQQTvdLw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=OPTnXOxt; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="OPTnXOxt" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=0AMBUI0pkHIlozu33qNSwEjssVugwAFn0k7gmS65+Tk=; b=OPTnXOxttEqQHGWdfiMgFAY85n IRX7WnBXAE/qlCH81CoW4+g7FDPqsU210mPTFYyOY+ZLyosen4fBL0ilYF5wwH1hdJrrR7W+kcmHP YmLPyS69h/2PoXfbzgQcYu7mhum1G/VbJ36GgBMebOpMk84ygJSnNauWXRFCiX7ucqg4iB3jPkYtA 5f4tyNmSeUIv5fiFUlg9SSxiLTIXX7CFaocl025VUTcyVnV+LGrSoArbd1j9zwM0adlqfdaGxqNUl tzgR+Zr1dzfXJN8/YbFjC3iBY34RpjZJbiL4dEq6vEUFflQJ1C+cMVLE70HtPW4Ag3b9fCF9qDVTh +KQiZI0w==; Received: from hch by bombadil.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tsFVe-00000007aIv-2N0P; Wed, 12 Mar 2025 06:24:06 +0000 Date: Tue, 11 Mar 2025 23:24:06 -0700 From: Christoph Hellwig To: Dave Chinner Cc: Ming Lei , Mikulas Patocka , Christoph Hellwig , Jens Axboe , Jooyung Han , Alasdair Kergon , Mike Snitzer , Heinz Mauelshagen , zkabelac@redhat.com, dm-devel@lists.linux.dev, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org Subject: Re: [PATCH] the dm-loop target Message-ID: References: <8adb8df2-0c75-592d-bc3e-5609bb8de8d8@redhat.com> <1fde6ab6-bfba-3dc4-d7fb-67074036deb0@redhat.com> <81b037c8-8fea-2d4c-0baf-d9aa18835063@redhat.com> Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Wed, Mar 12, 2025 at 01:34:02PM +1100, Dave Chinner wrote: > Wrong. > > Speculative non-blocking IO like NOWAIT is the wrong optimisation to > make for workloads that are very likely to block in the IO path. It > just adds overhead without adding any improvement in performance. Note that I suspect that most or at least many loop workloads are read-heavy. And at least for reads NOWAIT makes perfect sense. > Getting rid of the serialised IO submission problems that the loop > device current has will benefit *all* workloads that use the loop > device, not just those that are fully allocated. Yes, it won't quite > show the same performance as NOWAIT in that case, but it still > should give 90-95% of native performance for the static file case. > And it should also improve all the other cases, too, because now > they will only serialise when the backing file needs IO operations to > serialise (i.e. during allocation). And I agree that this should be a first step. > *cough* The whole ublk-zoned is a bit of a bullshit thing where Ming wrote up something that barely works to block inclusion of the zloop driver we really need for zoned xfs testing. Please don't take it serious.