* extent-status tree for DAX ?
@ 2017-02-20 6:25 Sanketh Nalli
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From: Sanketh Nalli @ 2017-02-20 6:25 UTC (permalink / raw)
To: linux-nvdimm
Hi,
I was wondering if we need the extent-status tree
for DAX-like devices ? Says here that it can get consume a lot of memory
and offer poor performance if the on-DAX file is fragmented. Without the status tree, one could simple walk the on-DAX extent tree to get to the file data pages and this is possible with DAX-like devices.
http://lxr.free-electrons.com/source/fs/ext4/extents_status.c#L117
A few simple experiments with filebench's random read workload clearly
bring out the difference in performance with a fragmented and contiguous
file on-DAX. A lot of time is spent in walking the status tree, which can be
avoided, I guess. Please let me know what you think.
--
S. Nalli
Graduate Student, Computer Sciences
University of Wisconsin-Madison, USA
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