From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH RFC - TAKE TWO - 12/12] block, bfq: boost the throughput with random I/O on NCQ-capable HDDs Date: Fri, 30 May 2014 11:51:05 -0400 Message-ID: <20140530155105.GF24871@htj.dyndns.org> References: <20140528221929.GG1419@htj.dyndns.org> <1401354343-5527-1-git-send-email-paolo.valente@unimore.it> <1401354343-5527-13-git-send-email-paolo.valente@unimore.it> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; bh=+QPdqPl+yVbc4yxIg/WMtNoZlDyiZV2I1Yj5SWiKjK4=; b=CuNVEPNVHpv4vbapBb5M3IzemgAv3GQOHXLfRK2mLUrzCZhfeKrf2AElmS5odlIyo3 cbY54ufsXivFGd1p4T4PJEOVFftB4fqqHhL4vieQeaLBNr+Ctyjmhu/wW7JxHShuRVV9 /KVDBNgXuFpG2Pyh6wxIa2tEny1VguBnRkKu1CkRFe4O+sx1n2Gi9eCvxYV6ndUAmzBK idYggVN76zpj0nRd7Hy1ZmsbM8kSAtVa2hT3tljJFe7ptYyWrRA3w2rXL0EHJ6Og97mT vDVf1O0DfUXSLFIUn+YyNld2g7TZCI/lsOKIlgYl187PbKbwiBbXt9Rk/GioTvGBMu+9 JSZw== Content-Disposition: inline In-Reply-To: <1401354343-5527-13-git-send-email-paolo.valente-rcYM44yAMweonA0d6jMUrA@public.gmane.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Paolo Valente Cc: Jens Axboe , containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Fabio Checconi , Arianna Avanzini , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Paolo Valente On Thu, May 29, 2014 at 11:05:43AM +0200, Paolo Valente wrote: > This patch is basically the counterpart of patch 13 for NCQ-capable > rotational devices. Exactly as patch 13 does on flash-based devices > and for any workload, this patch disables device idling on rotational > devices, but only for random I/O. More precisely, idling is disabled > only for constantly-seeky queues (see patch 7). In fact, only with > these queues disabling idling boosts the throughput on NCQ-capable > rotational devices. > > To not break service guarantees, idling is disabled for NCQ-enabled > rotational devices and constantly-seeky queues only when the same > symmetry conditions as in patch 13, plus an additional one, hold. The > additional condition is related to the fact that this patch disables > idling only for constantly-seeky queues. In fact, should idling be Wouldn't it make more sense to limit queue depth to one unless the workload can clearly benefit from allowing higher queue depth? And I really think it'd bring more clarity if we just concentrate on rotational devices. Thanks. -- tejun