On 09/21/2017 03:03 AM, Paolo Valente wrote: > Hi, > the first patch in this series fixes a bug that causes bfq to fail to > guarantee a high responsiveness on some drives, if there is heavy > random read+write I/O in the background. More precisely, such a > failure allowed this bug to be found [1], but the bug may well cause > other yet unreported anomalies. > > This fix uncovered other bugs that were concealed by the fixed bug, > for rather subtle reasons. These further bugs caused similar > responsiveness failures, but with sequential reaad+write workloads in > the background. The remaining three patches fix these further bugs. > > The sum of these fixes makes responsiveness much stabler with BFQ. In > the presence of write hogs, it is however still impossible for an I/O > scheduler to guarantee perfect responsiveness in any circustance, > because of throttling issues in the virtual-memory management > subsystem, and in other higher-level components. Added for 4.15, thanks. -- Jens Axboe
