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 65EEC188A3A; Tue, 17 Jun 2025 05:10:03 +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=1750137004; cv=none; b=UolYa2ozwD0HnL/ybnKX7AGTL+FQwg79ebSsS7Pd0FTi8CW4K0e3zbhqxi0caKqu2Jx/JgvT6IveqYgKKknnVYzjM0L62TjBl20vLDBoCCwkpjL8zhX1/mFv4f8j3aMvisJN9B0//AuOVakQTHlZ1HueAXVvMWRDR2k5JVdteqE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750137004; c=relaxed/simple; bh=e6F/U8KK+JHo5QqmKZF8HChaFF0qtrKFcOPjmUPZzbw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ip0WaMNOfkku02MTydhFfkNWx82RYBXYGpom0pw4EppAw1T4I7jWKxSTVrmW3iWiUhb1AmUf9dbSBVlX0qJb9DzXsoKfEjmu3Uo7zhM554KhoIYJGyfxq+gG+mA8RK9fUwDLPQDTAZ5fZrAhglPCBN/1PEwf61NHu3Dr5nT/45I= 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=2gcINPyO; 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="2gcINPyO" 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=DGMGg4G/vCV2eg1kp9R5xDSi1djMxRdxqFweh59FJEo=; b=2gcINPyOI9wJompQfi+CsRVQLi m67uComR4aqj/PS3FfM9xGyUC1qRq5JHshJEj7ZVfLdtc9sKqyxuW8j7UKiqze8ngqHg0aCoNj+KJ QySeBUehb0E0pQqXkf6rleydbiviw3u4i7SymVr+b2XneAjweD41xw9xYoG00cJkNUGrZZJ78uR3t TTgyziKtq2xAaiwUX2Dkc+r8nQnFmElIlksdlOkcJhAPNeRUZNIyyks0VEAGUfwXgd0uqNYS0I6ki 8T4e9mDB1pUDYk3D81kA2RIea1DuI4S7RhnYfMynY+5WhlcoNkDd297VVMQwNlzBAs5FFKXYchMJQ p8c53nMQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uROaA-00000006E2Z-3tTA; Tue, 17 Jun 2025 05:10:02 +0000 Date: Mon, 16 Jun 2025 22:10:02 -0700 From: Christoph Hellwig To: "Martin K. Petersen" Cc: Damien Le Moal , Jens Axboe , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@vger.kernel.org Subject: Re: [PATCH] block: Improve read ahead size for rotational devices Message-ID: References: <20250616062856.1629897-1-dlemoal@kernel.org> Precedence: bulk X-Mailing-List: linux-block@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 Mon, Jun 16, 2025 at 05:24:43PM -0400, Martin K. Petersen wrote: > > For a SCSI disk, this defaults to 2560 KB, which significantly improve > > performance for buffered reads. > > I believe this number came from a common RAID stripe configuration at > the time. However, it's really not a great default and has caused > problems with many devices that expect a power of two. Personally, I'd > like this default to be something like 2MB or 4MB. MD, DM, and most > hardware RAID devices report their stripe width correctly so the > existing "RAID-friendly" default really shouldn't be needed. Yeah, that number always felt weird. I'm all for using a more round value here. But as you said, separate isue.