From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?B?QmFydMWCb21pZWogxZp3acSZY2tp?= Subject: Re: Proposition - latency histogram Date: Mon, 9 Jan 2017 12:27:01 +0100 Message-ID: References: <69bf4eec-3959-f021-ad8f-d1b6d3e2ceaf@corp.ovh.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Return-path: Received: from 4.mo302.mail-out.ovh.net ([137.74.110.77]:57774 "EHLO 4.mo302.mail-out.ovh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935020AbdAIL1H (ORCPT ); Mon, 9 Jan 2017 06:27:07 -0500 Received: from EX4.OVH.local (gw1.corp.ovh.com [51.255.55.226]) by mo302.mail-out.ovh.net (Postfix) with ESMTPS id C72C8923 for ; Mon, 9 Jan 2017 12:27:04 +0100 (CET) In-Reply-To: <69bf4eec-3959-f021-ad8f-d1b6d3e2ceaf@corp.ovh.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Ceph Development Hi, I've made a simple implementation of performance histograms. Implementation is not very sophisticated but I think it could be a good start for more detailed discussion. Here's the PR: https://github.com/ceph/ceph/pull/12829 Regards, Bartek On 11/28/2016 05:22 PM, Bartłomiej Święcki wrote: > Hi, > > > Currently we can query OSD for op latency but it's given as an > average. Average may not give > the bets information in this case - i.e. spikes can easily get hidden > there. > > Instead of an average we could easily do a simple histogram - quantize > the latency into > predefined set of time intervals, for each of them have a simple > performance counter, > at each op increase one of them. Since those are per OSD, we could > have pretty high resolution > with fractional memory usage, performance impact should be negligible > since only one (two if split > into read and write) of those counters would be incremented per one > osd op. > > In addition we could also do this in 2D - each counter matching given > latency range and op size range. > having such 2D table would show both latency histogram, request size > histogram and combinations of those > (i.e. latency histogram of ~4k ops only). > > What do you think about this idea? I can prepare some code - a simple > proof of concept looks really > straightforward to implement. > > > Bartek > > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html