On Dec 6, 2016, at 6:13 AM, Renaud Mariana <rmariana@xxxxxxxxxx> wrote: > > Hello, > > We have noticed a HUGE slowdown when doing dpkg with ext4 over nbd (qemu-nbd as a server) > > dpkg times with default mkfs & mount options is : > > - ext4: 10 mn > - xfs : 30s. > > Disabling extents : > mkfs.ext4 -O ^extent > fixed the pb that is ext4 is as fast as xfs. > > Any ideas ? Is dpkg using fallocate() (uninitialized extents)? Could you strace the dpkg process with -fff to catch forked processes and search for fallocate() calls. fallocate() is the only thing I can think of that would make extents slower than block-mapped files. > Details : > > xnbd-client --blocksize 4096 qemu-nbd-ip 10000 /dev/nbd0 > mkfs.ext4 /dev/nbd0 > mount /dev/nbd0 /newroot > > wget https://download.elastic.co/kibana/kibana/kibana-4.6.1-amd64.deb > time dpkg -i kibana-4.6.1-amd64.deb What kernel version are you currently running? Is this problem new with this kernel (i.e. it worked fine with older kernels? > kibana installs many small files (23209 entries) under /opt/kibana How small are the files? Cheers, Andreas
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