On Thu, Mar 20, 2025 at 02:29:56PM +0100, Daniel Gomez wrote: > On Thu, Mar 20, 2025 at 12:11:47PM +0100, Matthew Wilcox wrote: > > On Thu, Mar 20, 2025 at 04:41:11AM -0700, Luis Chamberlain wrote: > > > We've been constrained to a max single 512 KiB IO for a while now on x86_64. > > ... > > > It does beg a few questions: > > > > > > - How are we computing the new max single IO anyway? Are we really > > > bounded only by what devices support? > > > - Do we believe this is the step in the right direction? > > > - Is 2 MiB a sensible max block sector size limit for the next few years? > > > - What other considerations should we have? > > > - Do we want something more deterministic for large folios for direct IO? > > > > Is the 512KiB limit one that real programs actually hit? Would we > > see any benefit from increasing it? A high end NVMe device has a > > bandwidth limit around 10GB/s, so that's reached around 20k IOPS, > > which is almost laughably low. > > Current devices do more than that. A quick search gives me 14GB/s and 2.5M IOPS > for gen5 devices: > > https://semiconductor.samsung.com/ssd/enterprise-ssd/pm1743/ > > An gen6 goes even further. That kind of misses my point. You don't need to exceed 512KiB I/Os to be bandwidth limited. So what's the ROI of all this work? Who benefits?
