On 2/3/2025 1:46 PM, Qu Wenruo wrote: >> ell for the WAF part, it'll save us 32 Bytes per FS sector (typically >> 4k) in the btrfs case, that's ~0.8% of the space. > > You forgot the csum tree COW part. > > Updating csum tree is pretty COW heavy and that's going to cause quite > some wearing. > > Thus although I do not think the RFC patch makes much sense compared to > just existing NODATASUM mount option, I'm interesting in the hardware > csum handling. But, patches do exactly that i.e., hardware cusm support. And posted numbers [*] are also when hardware is checksumming the data blocks. NODATASUM forgoes the data cums at Btrfs level, but its scope of control/influence ends there, as it knows nothing about what happens underneath. Proposed option (DATASUM_OFFLOAD) ensures that the [only] hardware checksums the data blocks. [*] https://lore.kernel.org/linux-block/20250129140207.22718-1-joshi.k@xxxxxxxxxxx/
