9:58 a.m.
On Wed, Dec 23, 2015 at 4:34 PM, Cholerae Hu <choleraehyq(a)gmail.com> wrote:
The block size is 1024.
# dumpe2fs -h /dev/pmem0 | grep "Block size"
dumpe2fs 1.42.13 (17-May-2015)
Block size: 1024
I tried it out on xfs and I succeeded. There are the prompting messages:
# mkfs.xfs -f -b size=1024 /dev/pmem0
meta-data=/dev/pmem0 isize=512 agcount=4, agsize=32768 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1
data = bsize=1024 blocks=131072, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal log bsize=1024 blocks=2571, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
# mount -o dax /dev/pmem0 /mnt/mem
The mount command doesn't return any message, and I can successfully read or
write files in /mnt/mem.
xfs will silently disable dax when the fs block size is too small,
i.e. your mmap() operations are backed by page cache in this case.
Currently the only indication of whether a mapping is DAX backed or
not is the presence of the VM_MIXEDMAP flag ("mm" in the VmFlags field
of /proc/<pid>/smaps)