On Mon, Apr 9, 2012 at 10:53 AM, Calvin Walton <calvin.wal...@kepstin.ca> 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? > mtrr_chunk_size=512M quiet > <snip> > [ 1.060117] udevd[695]: starting version 182 > [ 1.344328] device label Linux data devid 1 transid 611917 /dev/sda4 > [ 1.384888] dracut: Checking, if btrfs device complete > [ 1.405121] device label Linux data devid 1 transid 611917 /dev/sda4 > [ 1.405905] btrfs: disk space caching is enabled > [ 1.971953] device label Linux data devid 1 transid 611917 /dev/sda4 > [ 1.972519] btrfs: use lzo compression > [ 1.972523] btrfs: enabling auto defrag > [ 1.972526] btrfs: enabling inode map caching > [ 1.972528] btrfs: disk space caching is enabled > [ 2.528540] dracut: Checking btrfs: > /dev/disk/by-uuid/43969cd0-4aca-4297-bfbe-952a692f7d55 > [ 2.530725] dracut: trying to mount > /dev/disk/by-uuid/43969cd0-4aca-4297-bfbe-952a692f7d55 > [ 2.558285] device label Linux data devid 1 transid 611917 /dev/sda4 > [ 2.559087] btrfs: disk space caching is enabled > [ 3.013103] dracut: btrfs: > /dev/disk/by-uuid/43969cd0-4aca-4297-bfbe-952a692f7d55 is clean > [ 3.518807] dracut: Remounting > /dev/disk/by-uuid/43969cd0-4aca-4297-bfbe-952a692f7d55 with -o > subvolid=262,compress=lzo,autodefrag,space_cache,inode_cache,noatime,ro > [ 3.520031] device label Linux data devid 1 transid 611920 /dev/sda4 > [ 3.520680] btrfs: use lzo compression > [ 3.520684] btrfs: enabling auto defrag > [ 3.520688] btrfs: enabling inode map caching > [ 3.520689] btrfs: disk space caching is enabled > [ 4.066285] dracut: Mounted root filesystem /dev/sda4 > [ 4.120861] dracut: Switching root > [ 4.995934] btrfs: use lzo compression > [ 4.995938] btrfs: enabling auto defrag > [ 4.995942] btrfs: enabling inode map caching > [ 4.995943] btrfs: disk space caching is enabled > [ 5.010473] udevd[1330]: starting version 182 > > -- > Calvin Walton <calvin.wal...@kepstin.ca> -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
