From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from [195.159.176.226] ([195.159.176.226]:41618 "EHLO blaine.gmane.org" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1750859AbdDACmi (ORCPT ); Fri, 31 Mar 2017 22:42:38 -0400 Received: from list by blaine.gmane.org with local (Exim 4.84_2) (envelope-from ) id 1cu8zg-0000Vj-Rd for linux-btrfs@vger.kernel.org; Sat, 01 Apr 2017 04:42:24 +0200 To: linux-btrfs@vger.kernel.org From: Duncan <1i5t5.duncan@cox.net> Subject: Re: Shrinking a device - performance? Date: Sat, 1 Apr 2017 02:42:19 +0000 (UTC) Message-ID: References: <1CCB3887-A88C-41C1-A8EA-514146828A42@flyingcircus.io> <20170327130730.GN11714@carfax.org.uk> <3558CE2F-0B8F-437B-966C-11C1392B81F2@flyingcircus.io> <20170327194847.5c0c5545@natsu> <4E13254F-FDE8-47F7-A495-53BFED814C81@flyingcircus.io> <22746.30348.324000.636753@tree.ty.sabi.co.uk> <43e29da2-1d1b-1680-f262-1c95575645d8@gmail.com> <22749.10893.729399.275210@tree.ty.sabi.co.uk> <22750.37100.788020.938846@tree.ty.sabi.co.uk> <22750.48060.805852.28370@tree.ty.sabi.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: GWB posted on Fri, 31 Mar 2017 19:02:40 -0500 as excerpted: > It is confusing, and now that I look at it, more than a little funny. > Your use of xargs returns the size of the kernel module for each of the > filesystem types. I think I get it now: you are pointing to how large > the kernel module for btrfs is compared to other file system kernel > modules, 833 megs (piping find through xargs to sed). That does not > mean the btrfs kernel module can accommodate an upper limit of a command > line length that is 833 megs. It is just a very big loadable kernel > module. Umm... 833 K, not M, I believe. (The unit is bytes not KiB.) Because if just one kernel module is nearing a gigabyte, then the kernel must be many gigabytes either monolithic or once assembled in memory, and it just ain't so. But FWIW megs was my first-glance impression too, until my brain said "No way! Doesn't work!" and I took a second look. The kernel may indeed no longer fit on a 1.44 MB floppy, but it's still got a ways to go before it's multiple GiB! =:^) While they're XZ- compressed, I'm still fitting several monolithic-build kernels including their appended initramfs, along with grub, its config and modules, and a few other misc things, in a quarter-GB dup-mode btrfs, meaning 128 MiB capacity, including the 16 MiB system chunk so 112 MiB for data and metadata. That simply wouldn't be possible if the kernel itself were multi-GB, even uncompressed. Even XZ isn't /that/ good! -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman