On 3/17/23 23:29, Christoph Hellwig wrote:
On Fri, Mar 17, 2023 at 12:59:36PM -0700, Bart Van Assche wrote:
For zoned storage it is essential that split bios are submitted in LBA order.
This patch series realizes this by modifying __bio_split_to_limits() such that
it submits the first bio fragment and returns the remainder instead of
submitting the remainder and returning the first bio fragment. Please consider
this patch series for the next merge window.
Why are you sending large writes using REQ_OP_WRITE and not
using REQ_OP_ZONE_APPEND which side steps all these issues?
Hi Christoph,
How to achieve optimal performance with REQ_OP_ZONE_APPEND for SCSI
devices? My understanding of how REQ_OP_ZONE_APPEND works for SCSI
devices is as follows:
* ATA devices cannot support this operation directly because there are
not enough bits in the ATA sense data to report where appended data
has been written.
* T10 has not yet started with standardizing a zone append operation.
* The code that emulates REQ_OP_ZONE_APPEND for SCSI devices (in
sd_zbc.c) serializes REQ_OP_ZONE_APPEND operations (QD=1).
* To achieve optimal performance, QD > 1 is required.
Thanks,
Bart.
