On Wed, Apr 11, 2012 at 11:38:33AM -0500, Chester wrote: > On Mon, Apr 9, 2012 at 10:53 AM, Calvin Walton <calvin.walton@xxxxxxxxxx> wrote: > > > > Hi, > > > > I have a system that's using a dracut-generated initramfs to mount a > > btrfs root. After upgrading to kernel 3.4.0-rc2 to test it out, I've > > noticed that the process of mounting the root filesystem takes much > > longer with 3.4.0-rc2 than it did with 3.3.1 - nearly 30 seconds slower! > > > > Does anyone have any ideas? I'm going to try bisecting the issue to see > > if I can narrow down the cause. I've included excerpts from dmesg of the > > bad and good kernels here, and attached the complete dmesg from the bad > > kernel, in case it has anything interesting that I've trimmed out here. > > > > slow: > > [ 0.000000] Linux version 3.4.0-rc2 (cwalton@ayu) (gcc version 4.6.3 > > (Exherbo gcc-4.6.3) ) #57 SMP PREEMPT Mon Apr 9 11:19:43 EDT 2012 > > [ 0.000000] Command line: > > root=UUID=43969cd0-4aca-4297-bfbe-952a692f7d55 > > rootflags=subvolid=262,compress=lzo,autodefrag,space_cache,inode_cache,noatime > > mtrr_chunk_size=512M quiet > > <snip> > > [ 1.058257] udevd[701]: starting version 182 > > [ 1.389606] device label Linux data devid 1 transid 611923 /dev/sda4 > > [ 1.498659] dracut: Checking, if btrfs device complete > > [ 1.644808] device label Linux data devid 1 transid 611923 /dev/sda4 > > [ 1.647993] btrfs: disk space caching is enabled > > [ 2.180836] device label Linux data devid 1 transid 611923 /dev/sda4 > > [ 2.181663] btrfs: use lzo compression > > [ 2.181667] btrfs: enabling auto defrag > > [ 2.181670] btrfs: enabling inode map caching > > [ 2.181672] btrfs: disk space caching is enabled > > [ 2.697845] dracut: Checking btrfs: > > /dev/disk/by-uuid/43969cd0-4aca-4297-bfbe-952a692f7d55 > > [ 2.699999] dracut: trying to mount > > /dev/disk/by-uuid/43969cd0-4aca-4297-bfbe-952a692f7d55 > > [ 2.702637] device label Linux data devid 1 transid 611923 /dev/sda4 > > [ 2.704376] btrfs: disk space caching is enabled > > [ 3.081720] dracut: btrfs: > > /dev/disk/by-uuid/43969cd0-4aca-4297-bfbe-952a692f7d55 is clean > > [ 29.934639] dracut: Remounting > > /dev/disk/by-uuid/43969cd0-4aca-4297-bfbe-952a692f7d55 with -o > > subvolid=262,compress=lzo,autodefrag,space_cache,inode_cache,noatime,ro > > [ 29.936810] device label Linux data devid 1 transid 611926 /dev/sda4 > > [ 29.937720] btrfs: use lzo compression > > [ 29.937726] btrfs: enabling auto defrag > > [ 29.937733] btrfs: enabling inode map caching > > [ 29.937735] btrfs: disk space caching is enabled > > [ 30.388066] dracut: Mounted root filesystem /dev/sda4 > > [ 30.461884] dracut: Switching root > > [ 31.241729] udevd[1322]: starting version 182 > > [ 31.422905] btrfs: use lzo compression > > [ 31.422909] btrfs: enabling auto defrag > > [ 31.422913] btrfs: enabling inode map caching > > [ 31.422915] btrfs: disk space caching is enabled > > > > vs fast: > > [ 0.000000] Linux version 3.3.1 (cwalton@ayu) (gcc version 4.6.3 > > (Exherbo gcc-4.6.3) ) #53 SMP PREEMPT Wed Apr 4 01:20:47 EDT 2012 > > [ 0.000000] Command line: > > root=UUID=43969cd0-4aca-4297-bfbe-952a692f7d55 > > rootflags=subvolid=262,compress=lzo,autodefrag,space_cache,inode_cache,noatime > > Calvin, I noticed that you have the space_cache mount option set. I > remember josef saying that it is a one-time option where it's a > permanent change after mounting for the first time, therefore each > subsequent mount will not require the option. In fact, if the option > is specified again, the space_cache is reset. > > Is this still up-to-date info? > No you can leave space_cache set, there's another option for resetting the space cache, clear_cache iirc. Thanks, Josef -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
