[ adding Martin, given his hint infrastructure that is in the works... ] On Fri, May 13, 2016 at 5:02 PM, Jon Derrick <jonathan.derrick@xxxxxxxxx> wrote: > S_HIPRI is a hint that indicates the file (currently only block devices) > is a high priority file. This hint allows direct-io to the block device > to poll for completions if polling is available to the block device. > > The motivation for this patch comes from tiered caching solutions. A > user may wish to have low-latency block devices act as a cache for > higher-latency storage media. > > With the introduction of block polling, polling could be enabled on a > queue of a block device. The preadv2/pwritev2 sets allowed a user to > specify per-io polling, but removed the ability to poll per-queue. > > Instead of having a user modify their software to use preadv2/pwritev2, > this patch allows a user to set S_HIPRI on a block device file to request > all direct-io for this file to be polled. Setting aside whether this should be a per-task ioprio hint vs a block device inode hint, this single flag loses the granularity of whether reads or writes are polled. Low latency reads with posted writes seems a valid configuration. -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
