On 12/20/17 4:38 AM, Paolo Valente wrote: > Hi, > the main patch in this series ("block, bfq: let a queue be merged only > shortly after starting I/O") eliminates an outlier in the application > start-up time guaranteed by BFQ. This outlier occurs more or less > frequently, as a function of the characteristics of the system, and is > caused by a wrong detection of so-called cooperating processes > (details in the commit message). This main patch is preceded by two > patches that fix two bugs found while working on this problem. The > patch is then followed by a further, optimization patch, that removes > an operation made superfluous by the main patch. > > Jens, I've not forgotten our decision to make a patch that enables > blkio stats (related to proportional-share policy) to not be enabled > at boot, or when CFQ or BFQ modules are loaded. Just, we have already > prepared the present patches, plus a few other patches for improving > BFQ and fixing bugs, and I'd like to clear this backlog first. > > In this respect, after a patch for boosting throughput more reliably > with cooperating processes, I'll send out a patch to solve an > important read starvation problem. If I'm not making a blunder, this > problem affects every I/O scheduler in blk-mq. As a first step, I'll > propose a fix for BFQ. If the fix is ok, I'm willing to port it to the > other schedulers.
Added for 4.16, thanks. -- Jens Axboe