From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (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 8677B361668; Tue, 25 Aug 2026 06:57:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787641071; cv=none; b=OF8kbzYJukEZsIgN7uMlITohtxmg8Zab8CWrDc8YyJSK94qq+QDqgEfQofl0r82HesKfaZtwdboWpjRFxK/VU9IM5hu66IhlyhED2KSyiBFWokYsRybXK0Hhya1p7WtsS6xDd/X98XPdM0dfE4HbYOrcfsMWvbjX+zAT+NWWIfI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787641071; c=relaxed/simple; bh=l/JRAod7mcBLilL/tCxlbykTE5OwoELDGlJp6rgCQsA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=rwNDlyLiGcjP/Rz/aT5D1+PwCovtB5WqWQV7eKyJymftjBgHOKIK2Z51pEI40Qy+v02FTHVWvKWe2uYOMKCIT2y4c3yqJGSDAEJ8BKs5QxR4SGppJdCpC+YOL062Dqa/PueflRJKyUIzXcXUn7lPe2/lWHNY+BcRGZk98vuMLX4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de Received: by verein.lst.de (Postfix, from userid 2407) id 05BEF68BFE; Tue, 25 Aug 2026 08:57:46 +0200 (CEST) Date: Tue, 25 Aug 2026 08:57:45 +0200 From: Christoph Hellwig To: Kanchan Joshi Cc: Christoph Hellwig , brauner@kernel.org, djwong@kernel.org, dgc@kernel.org, jack@suse.cz, cem@kernel.org, axboe@kernel.dk, kbusch@kernel.org, ritesh.list@gmail.com, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, gost.dev@samsung.com Subject: Re: [PATCH v4 5/6] xfs: write stream based AG placement Message-ID: <20260825065745.GB24808@lst.de> References: <20260717125538.508925-1-joshi.k@samsung.com> <20260717125538.508925-6-joshi.k@samsung.com> <20260819072902.GA2332@lst.de> Precedence: bulk X-Mailing-List: linux-xfs@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: User-Agent: Mutt/1.5.17 (2007-11-01) On Fri, Aug 21, 2026 at 06:03:29PM +0530, Kanchan Joshi wrote: > On 8/19/2026 12:59 PM, Christoph Hellwig wrote: > > On Fri, Jul 17, 2026 at 06:25:37PM +0530, Kanchan Joshi wrote: > >> If AGs are fewer than write streams, write streams are distributed into > >> available AGs in round robin fashion. > > > > I think we should just limit the number of available write streams > > to the number of AG, as otherwise we'll get into a bit of a mess. > > To confirm: given above quoting, for the other two cases (i.e., Streams > <= AGs), are you open to stream-based AG-sets modulo inode hashing (that > you suggested to skip in previous patch)? Yes. Even inode hashing might be ok, but I think it mostly papers over other issues. > And is this point only for the case when Streams > AGs? Yes. > This case can happen for hw streams, but for pure software streams, we > will not hit this case because the filesystem determines the stream > count based on the AG count. Right. > > > And for the case of the hardware write streams query them in mkfs > > to align the AG geometry to that. > > If this is only for the streams > AGs case, the filesystem can just > clamp down to match, turning it into a 'streams = AGs' case. > And that means no changes in mkfs. Is that fine? Well, it is fine. But number of available write streams might be a very useful hint to mkfs as mkfs tries to guess the available concurrent, and the write streams are how the device exposes that.