On Tue, Jun 3, 2025 at 6:54 PM Christoph Hellwig <h...@lst.de> wrote: > > On Tue, Jun 03, 2025 at 02:46:20PM +0530, Anuj Gupta/Anuj Gupta wrote: > > On 6/2/2025 7:49 PM, Christoph Hellwig wrote: > > > On Thu, May 29, 2025 at 04:44:51PM +0530, Kundan Kumar wrote: > > > Well, the proper thing would be to figure out a good default and not > > > just keep things as-is, no? > > > > We observed that some filesystems, such as Btrfs, don't benefit from > > this infra due to their distinct writeback architecture. To preserve > > current behavior and avoid unintended changes for such filesystems, > > we have kept nr_wb_ctx=1 as the default. Filesystems that can take > > advantage of parallel writeback (xfs, ext4) can opt-in via a mount > > option. Also we wanted to reduce risk during initial integration and > > hence kept it as opt-in. > > A mount option is about the worst possible interface for behavior > that depends on file system implementation and possibly hardware > chacteristics. This needs to be set by the file systems, possibly > using generic helpers using hardware information.
Right, that makes sense. Instead of using a mount option, we can introduce generic helpers to initialize multiple writeback contexts based on underlying hardware characteristics — e.g., number of CPUs or NUMA topology. Filesystems like XFS and EXT4 can then call these helpers during mount to opt into parallel writeback in a controlled way. > > > Used PMEM of 6G > > battery/capacitor backed DRAM, or optane? We emulated PMEM using DRAM by following the steps here: https://www.intel.com/content/www/us/en/developer/articles/training/how-to-emulate-persistent-memory-on-an-intel-architecture-server.html > > > > > and NVMe SSD of 3.84 TB > > Consumer drive, enterprise drive? It's an enterprise-grade drive — Samsung PM1733 > > > For xfs used this command: > > xfs_io -c "stat" /mnt/testfile > > And for ext4 used this: > > filefrag /mnt/testfile > > filefrag merges contiguous extents, and only counts up for discontiguous > mappings, while fsxattr.nextents counts all extent even if they are > contiguous. So you probably want to use filefrag for both cases. Got it — thanks for the clarification. We'll switch to using filefrag and will share updated extent count numbers accordingly. _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
