On Mon, Jan 04, 2021 at 09:44:15AM +0100, Christoph Hellwig wrote: > On Wed, Dec 30, 2020 at 08:08:15AM +0800, Ming Lei wrote: > > It is observed that __block_write_full_page() always submit bio with size > > of block size, > > which is often 512 bytes. > > > > In case of sequential IO, or >=4k BS random/seq writeback IO, most of times > > IO > > represented by all buffer_head in each page can be done in single bio. It > > is actually > > done in single request IO by block layer's plug merge too. > > > > So check if IO represented by buffer_head can be merged to single page > > IO, if yes, just submit single bio instead of submitting one bio for each > > buffer_head. > > There is some very weird formatting in here. From a very quick look > the changes look sensible, but I wonder if we should spend so much > time optimizing the legacy buffer_head I/O path, rather than switching > callers to saner helpers.
It may take long to convert fs code into iomap, and I understand fs/block_dev.c can't be converted to iomap until all FS removes buffer_head, correct me if it is wrong. Thanks, Ming
