On Tue, 30 Apr 2024 15:16:24 -0600, Uday Shankar wrote:
> ublk_drv currently creates block devices with the default max_segments
> and max_segment_size limits of BLK_MAX_SEGMENTS (128) and
> BLK_MAX_SEGMENT_SIZE (65536) respectively. These defaults can
> artificially constrain the I/O size seen by the ublk server - for
> example, suppose that the ublk server has configured itself to accept
> I/Os up to 1M and the application is also issuing 1M sized I/Os. If the
> I/O buffer used by the application is backed by 4K pages, the buffer
> could consist of up to 1M / 4K = 256 physically discontiguous segments
> (even if the buffer is virtually contiguous). As such, the I/O could
> exceed the default max_segments limit and get split. This can cause
> unnecessary performance issues if the ublk server is optimized to handle
> 1M I/Os. The block layer's segment count/size limits exist to model
> hardware constraints which don't exist in ublk_drv's case, so just
> remove those limits for the block devices created by ublk_drv.
>
> [...]
Applied, thanks!
[1/1] ublk: remove segment count and size limits
commit: eaf4a9b19b9961f8ca294c39c5f8984a4cf42212
Best regards,
--
Jens Axboe
