From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH V7 4/6] blk-mq: introduce .get_budget and .put_budget in blk_mq_ops To: Hannes Reinecke , Ming Lei Cc: "linux-kernel@vger.kernel.org" , "linux-block@vger.kernel.org" , "hch@infradead.org" , "tom81094@gmail.com" , "himanshu.madhani@cavium.com" , "paolo.valente@linaro.org" , "axboe@kernel.dk" , "linux-scsi@vger.kernel.org" , "oleksandr@natalenko.name" , "john.garry@huawei.com" , "osandov@fb.com" , "loberman@redhat.com" , "james.smart@broadcom.com" References: <20171012183704.22326-5-ming.lei@redhat.com> <9a741c03-90a3-e583-ddde-0ed71c8570a2@kernel.dk> <20171013001919.GA24715@ming.t460p> <6efdb459-8746-562d-06dc-5b3e172076e1@kernel.dk> <20171013160731.GA30899@ming.t460p> <1507912260.13345.0.camel@wdc.com> <20171013164519.GF30899@ming.t460p> <1507914527.13345.17.camel@wdc.com> <20171013172950.GA32319@ming.t460p> <515ca83f-5629-31e2-ef70-1869ae1b75ef@suse.de> <20171017012922.GD15996@ming.t460p> <6e8162a0-6ff3-2691-af79-13548a8834c6@suse.de> From: Bart Van Assche Message-ID: <782e3b9b-2aae-e013-bedc-3c35cb0f7edd@wdc.com> Date: Tue, 17 Oct 2017 11:09:15 -0700 MIME-Version: 1.0 In-Reply-To: <6e8162a0-6ff3-2691-af79-13548a8834c6@suse.de> Content-Type: text/plain; charset=utf-8; format=flowed List-ID: On 10/16/17 23:38, Hannes Reinecke wrote: > Again, these are just some pre-defined values to avoid I/O starvation > when having several LUNs. _if_ we can guarantee I/O fairness between > several (hundreds!) devices all sharing the same tagspace we wouldn't > need these variables. I think we already have two mechanisms for guaranteeing I/O fairness: * Scsi_Host.starved_list for both the legacy SCSI core and scsi-mq. * For scsi-mq, the active_queues counter in the blk-mq core. See also hctx_may_queue(). Bart.