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 911E12116FB for ; Wed, 22 Jan 2025 14:11:57 +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=1737555119; cv=none; b=qaezrTPjnqD7oH4mV+k4B08WZi3G5vTUJ0d4nAtZDake5bG3G0Lco86foisBWHZaqqT4KQA+MO44Z8peCM7RPzual+Zc4gE7OSvC5ZwylAvnmTQdB7XBz0Ju9ZCMk5sJ1aeKMCRUT7W+TRUNyR4hfmHmpA1jiRL0AMc/Wm8P4KE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737555119; c=relaxed/simple; bh=DFrXRjKIj3f3mhPNILm4u9uZq33Aky+99DxS3xnzbB4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=EWsekPK4ORHKt25JUBDzmKj+Sy3CTeuBov6L+321SSILtJfSI8f84DRB/Bdrwi0W3rEDV/+TJmZgAyAd94/9vskLluIIkFSuZyNKT4heKol1J68B38u/dN9rP5k5dFUpbleuCMumGm2HVLmVwOfhq1JSBngdWwTC6EZanam/0Nk= 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=jrHCE2CA; 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="jrHCE2CA" 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=DFrXRjKIj3f3mhPNILm4u9uZq33Aky+99DxS3xnzbB4=; b=jrHCE2CAdRQBtTYWVCCb5ZX2N6 hDA2rvwuk7gfTA+RpZkj/DAOBA2zYD3xkPwpUcNFAtd/JkjqIRrnBfbyGidyJ2rylC1HomFkINPi+ Pt5xVw+YbumdNv7ie80cHPwYWzyjdOtaxvOWIBaxNBqX/SLhBfoIAENZsOJUoOyusuYntjrLa8MJO fCJ7kRLXR9eCjiCEyHs1pw2DemlbvrBGObIBXOEdbi9xmALGlPQtxnf+iVKo4LKzyAj4XAWYNnU9c MySLIIYZCyAzcYc2essBszwihjRKEtYXvL04JYQGeQccjutpprXXE549stWV5By7usQzda8M/RZPt alU7G4+Q==; Received: from hch by bombadil.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tabSV-0000000AO1e-3SjZ; Wed, 22 Jan 2025 14:11:55 +0000 Date: Wed, 22 Jan 2025 06:11:55 -0800 From: Christoph Hellwig To: Theodore Ts'o Cc: Christoph Hellwig , Gerhard Wiesinger , linux-ext4@vger.kernel.org Subject: Re: Transparent compression with ext4 - especially with zstd Message-ID: References: <8cb4d855-6bd8-427f-ac8f-8cf7b91547fb@wiesinger.com> <20250121040125.GC3761769@mit.edu> <213343dc-3911-45de-8195-469da9dd1a91@wiesinger.com> <20250121193351.GA3820043@mit.edu> <20250122131912.GA3844227@mit.edu> Precedence: bulk X-Mailing-List: linux-ext4@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: <20250122131912.GA3844227@mit.edu> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Wed, Jan 22, 2025 at 08:19:12AM -0500, Theodore Ts'o wrote: > ... but out of place writes means that every single fdatasync() called > by the database now requires a file system level transaction commits. Yes. > So now every single fdatasync(2) results in the data blocks getting > written out to a new location on disk (this is what out of place > writes mean), followed by a CACHE FLUSH, followed by the metadata > updates to point at the new location on the disk, first written to the > file system tranaction log, followed by the fs commit block, followed > by a *second* CACHE FLUSH command. Or you put the compressed data in the log and have a single FUA write.