| Message ID | 20171220113834.2578-1-paolo.valente@linaro.org |
|---|---|
| Headers | show |
| Series | remove start-up time outlier caused by wrong detection of cooperating processes | expand |
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
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. Thanks, Paolo Angelo Ruocco (2): block, bfq: check low_latency flag in bfq_bfqq_save_state() block, bfq: remove superfluous check in queue-merging setup Paolo Valente (2): block, bfq: add missing rq_pos_tree update on rq removal block, bfq: let a queue be merged only shortly after starting I/O block/bfq-iosched.c | 98 ++++++++++++++++++++++++++++++----------------------- block/bfq-iosched.h | 2 ++ block/bfq-wf2q.c | 4 +++ 3 files changed, 61 insertions(+), 43 deletions(-) -- 2.15.1