Hi,

I am encountering problems when continuously writing larger amounts of
data to a USB flash drive. My configuration is

x86-64 kernel
USB stick with 10MB/s write, 30MB/s read speed,
HDD with ~60-80MB/s read/write
8 GiB RAM

When copying 4GB or more in one go from HDD to Flash, during the
copying, fork() and probably other syscalls involving VM start
blocking (I first observed the problem in Chrome, which refused to
display content in new tabs). When one lets the copying finish, the
system returns to a usable state.

During the limbo, khugepaged is in D state (uninterruptible sleep).

Syslog doesn't seem to contain anything of interest.

After

echo never > /sys/kernel/mm/transparent_hugepage/enabled

copying works ok.

Regards,
-- 
Jindrich Makovicka