On 2/2/24 12:37 AM, Damien Le Moal wrote: > On 2/2/24 16:30, Damien Le Moal wrote: >> The patch series introduces zone write plugging (ZWP) as the new >> mechanism to control the ordering of writes to zoned block devices. >> ZWP replaces zone write locking (ZWL) which is implemented only by >> mq-deadline today. ZWP also allows emulating zone append operations >> using regular writes for zoned devices that do not natively support this >> operation (e.g. SMR HDDs). This patch series removes the scsi disk >> driver and device mapper zone append emulation to use ZWP emulation. >> >> Unlike ZWL which operates on requests, ZWP operates on BIOs. A zone >> write plug is simply a BIO list that is atomically manipulated using a >> spinlock and a kblockd submission work. A write BIO to a zone is >> "plugged" to delay its execution if a write BIO for the same zone was >> already issued, that is, if a write request for the same zone is being >> executed. The next plugged BIO is unplugged and issued once the write >> request completes. >> >> This mechanism allows to: >> - Untangle zone write ordering from the block IO schedulers. This >> allows removing the restriction on using only mq-deadline for zoned >> block devices. Any block IO scheduler, including "none" can be used. >> - Zone write plugging operates on BIOs instead of requests. Plugged >> BIOs waiting for execution thus do not hold scheduling tags and thus >> do not prevent other BIOs from being submitted to the device (reads >> or writes to other zones). Depending on the workload, this can >> significantly improve the device use and the performance. >> - Both blk-mq (request) based zoned devices and BIO-based devices (e.g. >> device mapper) can use ZWP. It is mandatory for the >> former but optional for the latter: BIO-based driver can use zone >> write plugging to implement write ordering guarantees, or the drivers >> can implement their own if needed. >> - The code is less invasive in the block layer and in device drivers. >> ZWP implementation is mostly limited to blk-zoned.c, with some small >> changes in blk-mq.c, blk-merge.c and bio.c. >> >> Performance evaluation results are shown below. >> >> The series is organized as follows: > > I forgot to mention that the patches are against Jens block/for-next > branch with the addition of Christoph's "clean up blk_mq_submit_bio" > patches [1] and my patch "null_blk: Always split BIOs to respect queue > limits" [2]. I figured that was the case, I'll get both of these properly setup in a for-6.9/block branch, just wanted -rc3 to get cut first. JFYI that they are coming tomorrow. -- Jens Axboe
