On Sun, Apr 3, 2011 at 21:40, Eric Sandeen <sandeen@xxxxxxxxxx> wrote: > On 4/3/11 11:07 AM, Zeev Tarantov wrote: >> While testing zram I ran a script that creates a block devices, >> creates a filesystem on in and untars Qt on that filesystem. >> I was surprised to find ext4_mb_scan_aligned near the top of the profile output. >> This was evidently because the command "mke2fs -t ext4 -m 0 -I 128 -O >> ^has_journal,^ext_attr <block device>" >> created a filesystem with (output of tune2fs): >> RAID stride: 1 >> RAID stripe width: 1 > > mke2fs queries the block device for its geometry, based on what is > reported via sysfs: > > /* > * Sets the geometry of a device (stripe/stride), and returns the > * device's alignment offset, if any, or a negative error. > */ > static int get_device_geometry( ... > ... > min_io = blkid_topology_get_minimum_io_size(tp); > opt_io = blkid_topology_get_optimal_io_size(tp); > ... > > fs_param->s_raid_stride = min_io / blocksize; > fs_param->s_raid_stripe_width = opt_io / blocksize; > > What does > > # blockdev --getiomin --getioopt /dev/<yourdevice> > > say for your device? get logical block (sector) size: 4096 get physical block (sector) size: 4096 get minimum I/O size: 4096 get optimal I/O size: 4096 get alignment offset in bytes: 0 get max sectors per request: 255 get blocksize: 4096 get readahead: 256 > The device may be reporting odd values, but mke2fs probably > should be smart enough not to set block-sized stripe unit and width... If the filesystem created with the default options is slow or has higher cpu usage, it should be changed. > -Eric -Z.T. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
