From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932656AbeARPXS (ORCPT ); Thu, 18 Jan 2018 10:23:18 -0500 Received: from mail-it0-f49.google.com ([209.85.214.49]:41322 "EHLO mail-it0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932124AbeARPXQ (ORCPT ); Thu, 18 Jan 2018 10:23:16 -0500 X-Google-Smtp-Source: ACJfBoueiLRf0bqzPAA7wM6He6PVBsUlGyK6vL20HgnJXZ7UTRtSu+yb9acx4+K9t4xIbEBARgfGVw== Subject: Re: [PATCH BUGFIX/IMPROVEMENT 0/2] block, bfq: two pending patches To: Paolo Valente Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, ulf.hansson@linaro.org, broonie@kernel.org, linus.walleij@linaro.org, bfq-iosched@googlegroups.com, oleksandr@natalenko.name References: <20180113110518.2519-1-paolo.valente@linaro.org> From: Jens Axboe Message-ID: <55d37f66-019d-2ded-2559-16930466d644@kernel.dk> Date: Thu, 18 Jan 2018 08:23:12 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:58.0) Gecko/20100101 Thunderbird/58.0 MIME-Version: 1.0 In-Reply-To: <20180113110518.2519-1-paolo.valente@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/13/18 4:05 AM, Paolo Valente wrote: > Hi Jens, > here are again the two pending patches you asked me to resend [1]. One > of them, fixing read-starvation problems, was accompanied by a cover > letter. I'm pasting the content of that cover letter below. > > The patch addresses (serious) starvation problems caused by > request-tag exhaustion, as explained in more detail in the commit > message. I started from the solution in the function > kyber_limit_depth, but then I had to define more articulate limits, to > counter starvation also in cases not covered in kyber_limit_depth. > If this solution proves to be effective, I'm willing to port it > somehow to the other schedulers. It's something we've been doing in the old request layer for tagging for a long time (more than a decade), so a generic (and fast) solution that covers all cases for blk-mq-tag would indeed be great. For now, I have applied these for 4.16, thanks. -- Jens Axboe