On Fri, May 30 2014 at 10:26am -0400, Richard W.M. Jones <rjones@redhat.com> wrote: > On Fri, May 30, 2014 at 03:54:49PM +0200, Heinz Mauelshagen wrote: > > On 05/30/2014 03:46 PM, Richard W.M. Jones wrote: > > >I have now set both read_promote_adjustment == > > >write_promote_adjustment == 0 and used drop_caches between runs. > > > > Did you adjust "sequential_threshold 0" as well? > > > > dm-cache tries to avoid promoting large sequential files to the cache, > > because spindles have good bandwidth. > > > > This is again because of the hot spot caching nature of dm-cache. > > Setting this had no effect. > > I starting to wonder if my settings are having any effect at all. > > Here are the device-mapper tables: > > $ sudo dmsetup table > vg_guests-lv_cache_cdata: 0 419430400 linear 8:33 2099200 > vg_guests-lv_cache_cmeta: 0 2097152 linear 8:33 2048 > vg_guests-home: 0 209715200 linear 9:127 2048 > vg_guests-libvirt--images: 0 1677721600 cache 253:1 253:0 253:2 128 0 default 0 > vg_guests-libvirt--images_corig: 0 1677721600 linear 9:127 2055211008 > > And here is the command I used to set sequential_threshold to 0 > (there was no error and no other output): > > $ sudo dmsetup message vg_guests-libvirt--images 0 sequential_threshold 0 sequential_threshold is only going to help the md5sum's IO get promoted (assuming you're having it read a large file). > Is there a way to print the current settings? > > Could writethrough be enabled? (I'm supposed to be using writeback). > How do I find out? dmsetup status vg_guests-libvirt--images But I'm really wondering if your IO is misaligned (like my earlier email brought up). It _could_ be promoting 2 64K blocks from the origin for every 64K IO. _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
