Development Continues For Supporting EXT4 On NVDIMMs
Written by Michael Larabel in Free Software on 23 July 2014 at 04:51 AM EDT. 6 Comments
The large set of 22 patches for supporting the EXT4 file-system on non-volatile DIMM memory is now up to its eighth revision.

Matthew Wilcox and others have been working on allowing the EXT4 file-system to optimally use NVDIMM DRAM when it's treated as a block device. Currently the usage of EXT4 on NVDIMMs is sub-optimal, as explained by Wilcox, "One of the primary uses for NV-DIMMs is to expose them as a block device and use a filesystem to store files on the NV-DIMM. While that works, it currently wastes memory and CPU time buffering the files in the page cache. We have support in ext2 for bypassing the page cache, but it has some races which are unfixable in the current design. This series of patches rewrite the underlying support, and add support for direct access to ext4."

This direct access support for EXT4 and ported from the EXT2 implementation should significantly help out the popular Linux file-system when using NVDIMMs; the direct access (DAX) mode basically avoids double-buffering data before copying it to the device. While these patches are up to revision eight, they haven't yet been pulled into the EXT4 tree for merging into the mainline kernel, but for now can be found via the Linux kernel mailing list.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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