From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1C77CC433EF for ; Tue, 14 Sep 2021 13:13:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 004D0610CE for ; Tue, 14 Sep 2021 13:13:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233129AbhINNPO (ORCPT ); Tue, 14 Sep 2021 09:15:14 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:33894 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232996AbhINNPN (ORCPT ); Tue, 14 Sep 2021 09:15:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1631625236; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=leLSkIrrEsFMo2jZg6kQLxJHDrQI8srJo9wdr/QIasM=; b=R/1s+xJKhbn6RTlH/NpIKahEHsa8+S+caLiNFMwycNIO2AkfRcsaMH81xXVzhBFHGn12hd h7/chQUzG+aIN/pEqKw5sD1m+SH7WxOD1/sFi0Bczzt1/dbPAZPVVKmoADrOIIqrU4HPzG K91Z+SwMITNZ4zn1c6Ar6v5QzrfhUUQ= Received: from mail-pf1-f200.google.com (mail-pf1-f200.google.com [209.85.210.200]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-329-j2dcV7HKMXO8yvl0NpQ9zA-1; Tue, 14 Sep 2021 09:13:55 -0400 X-MC-Unique: j2dcV7HKMXO8yvl0NpQ9zA-1 Received: by mail-pf1-f200.google.com with SMTP id o130-20020a62cd88000000b004053c6c1765so8259968pfg.6 for ; Tue, 14 Sep 2021 06:13:55 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=leLSkIrrEsFMo2jZg6kQLxJHDrQI8srJo9wdr/QIasM=; b=UhpF863pawsjTb7nFbr8unkSlT17f6K/difDJK856OL6XFsy3JhnOWFiOkTl+PdTCh djormi0sgsEAM2H4Ug59cO4pErUD6VptF1m6ifTXbUsRbnli+SPwB1CeME6HqO2e1ENm QvxWet4aSfJeGu7udf0WNOo7yQGLFizYWEkjex2RZq9B+HN3xP94qjtwe+hE5eOpl86i AOLuow3xoVYijv+C5bXDX51d+ZVTg6agKH/KlrejXSUtmmD2MuXHaDFKCP6dFyw3PnTs QViaXs3sVHvRDXGtHAhvweUJ54oTFiUx1ZM5xhtwkBLSdjSw0iajLwQpBqAC4fRp/wX9 uoUQ== X-Gm-Message-State: AOAM5300GIk5FlyDguuEG8u1/8HBHuLbD8XoGcCi5lZQsh2rP7hfyCSh Zu0LNYomJi972dTGdx8fHt3gsGtu2k8A9pX+oYIqZplKVlrz5/egw2wrkZY9qLV10ha8fwEFQ2v ZF09fO28vLq5q+XGNrANu+1a/PxoyxbxrWTF7n101/okrUWIIakKTNLqBaLyCFsZ1sEJ8ccI= X-Received: by 2002:a65:44c5:: with SMTP id g5mr15513346pgs.39.1631625234084; Tue, 14 Sep 2021 06:13:54 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzYAJNVHBHah9Av7GtiWidqofHZ0DP3gR6mteLlOBOFFX9pGZIdnXXcXBQ8dN0NGal0StDjng== X-Received: by 2002:a65:44c5:: with SMTP id g5mr15513319pgs.39.1631625233663; Tue, 14 Sep 2021 06:13:53 -0700 (PDT) Received: from [10.72.12.89] ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id g16sm11078184pfj.19.2021.09.14.06.13.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 14 Sep 2021 06:13:53 -0700 (PDT) Subject: Re: [PATCH v2 2/4] ceph: track average/stdev r/w/m latency To: Venky Shankar , jlayton@redhat.com, pdonnell@redhat.com Cc: ceph-devel@vger.kernel.org References: <20210914084902.1618064-1-vshankar@redhat.com> <20210914084902.1618064-3-vshankar@redhat.com> From: Xiubo Li Message-ID: <7b7a93ad-4a45-4187-5220-709fee38b4ea@redhat.com> Date: Tue, 14 Sep 2021 21:13:48 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <20210914084902.1618064-3-vshankar@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org On 9/14/21 4:49 PM, Venky Shankar wrote: > The math involved in tracking average and standard deviation > for r/w/m latencies looks incorrect. Fix that up. Also, change > the variable name that tracks standard deviation (*_sq_sum) to > *_stdev. > > Signed-off-by: Venky Shankar > --- > fs/ceph/debugfs.c | 14 +++++----- > fs/ceph/metric.c | 70 ++++++++++++++++++++++------------------------- > fs/ceph/metric.h | 9 ++++-- > 3 files changed, 45 insertions(+), 48 deletions(-) > > diff --git a/fs/ceph/debugfs.c b/fs/ceph/debugfs.c > index 38b78b45811f..3abfa7ae8220 100644 > --- a/fs/ceph/debugfs.c > +++ b/fs/ceph/debugfs.c > @@ -152,7 +152,7 @@ static int metric_show(struct seq_file *s, void *p) > struct ceph_mds_client *mdsc = fsc->mdsc; > struct ceph_client_metric *m = &mdsc->metric; > int nr_caps = 0; > - s64 total, sum, avg, min, max, sq; > + s64 total, sum, avg, min, max, stdev; > u64 sum_sz, avg_sz, min_sz, max_sz; > > sum = percpu_counter_sum(&m->total_inodes); > @@ -175,9 +175,9 @@ static int metric_show(struct seq_file *s, void *p) > avg = total > 0 ? DIV64_U64_ROUND_CLOSEST(sum, total) : 0; > min = m->read_latency_min; > max = m->read_latency_max; > - sq = m->read_latency_sq_sum; > + stdev = m->read_latency_stdev; > spin_unlock(&m->read_metric_lock); > - CEPH_LAT_METRIC_SHOW("read", total, avg, min, max, sq); > + CEPH_LAT_METRIC_SHOW("read", total, avg, min, max, stdev); > > spin_lock(&m->write_metric_lock); > total = m->total_writes; > @@ -185,9 +185,9 @@ static int metric_show(struct seq_file *s, void *p) > avg = total > 0 ? DIV64_U64_ROUND_CLOSEST(sum, total) : 0; > min = m->write_latency_min; > max = m->write_latency_max; > - sq = m->write_latency_sq_sum; > + stdev = m->write_latency_stdev; > spin_unlock(&m->write_metric_lock); > - CEPH_LAT_METRIC_SHOW("write", total, avg, min, max, sq); > + CEPH_LAT_METRIC_SHOW("write", total, avg, min, max, stdev); > > spin_lock(&m->metadata_metric_lock); > total = m->total_metadatas; > @@ -195,9 +195,9 @@ static int metric_show(struct seq_file *s, void *p) > avg = total > 0 ? DIV64_U64_ROUND_CLOSEST(sum, total) : 0; > min = m->metadata_latency_min; > max = m->metadata_latency_max; > - sq = m->metadata_latency_sq_sum; > + stdev = m->metadata_latency_stdev; > spin_unlock(&m->metadata_metric_lock); > - CEPH_LAT_METRIC_SHOW("metadata", total, avg, min, max, sq); > + CEPH_LAT_METRIC_SHOW("metadata", total, avg, min, max, stdev); > > seq_printf(s, "\n"); > seq_printf(s, "item total avg_sz(bytes) min_sz(bytes) max_sz(bytes) total_sz(bytes)\n"); > diff --git a/fs/ceph/metric.c b/fs/ceph/metric.c > index 226dc38e2909..6b774b1a88ce 100644 > --- a/fs/ceph/metric.c > +++ b/fs/ceph/metric.c > @@ -244,7 +244,8 @@ int ceph_metric_init(struct ceph_client_metric *m) > goto err_i_caps_mis; > > spin_lock_init(&m->read_metric_lock); > - m->read_latency_sq_sum = 0; > + m->read_latency_stdev = 0; > + m->avg_read_latency = 0; > m->read_latency_min = KTIME_MAX; > m->read_latency_max = 0; > m->total_reads = 0; > @@ -254,7 +255,8 @@ int ceph_metric_init(struct ceph_client_metric *m) > m->read_size_sum = 0; > > spin_lock_init(&m->write_metric_lock); > - m->write_latency_sq_sum = 0; > + m->write_latency_stdev = 0; > + m->avg_write_latency = 0; > m->write_latency_min = KTIME_MAX; > m->write_latency_max = 0; > m->total_writes = 0; > @@ -264,7 +266,8 @@ int ceph_metric_init(struct ceph_client_metric *m) > m->write_size_sum = 0; > > spin_lock_init(&m->metadata_metric_lock); > - m->metadata_latency_sq_sum = 0; > + m->metadata_latency_stdev = 0; > + m->avg_metadata_latency = 0; > m->metadata_latency_min = KTIME_MAX; > m->metadata_latency_max = 0; > m->total_metadatas = 0; > @@ -322,20 +325,26 @@ void ceph_metric_destroy(struct ceph_client_metric *m) > max = new; \ > } > > -static inline void __update_stdev(ktime_t total, ktime_t lsum, > - ktime_t *sq_sump, ktime_t lat) > +static inline void __update_latency(ktime_t *ctotal, ktime_t *lsum, > + ktime_t *lavg, ktime_t *min, ktime_t *max, > + ktime_t *lstdev, ktime_t lat) > { > - ktime_t avg, sq; > + ktime_t total, avg, stdev; > > - if (unlikely(total == 1)) > - return; > + total = ++(*ctotal); > + *lsum += lat; > + > + METRIC_UPDATE_MIN_MAX(*min, *max, lat); > > - /* the sq is (lat - old_avg) * (lat - new_avg) */ > - avg = DIV64_U64_ROUND_CLOSEST((lsum - lat), (total - 1)); > - sq = lat - avg; > - avg = DIV64_U64_ROUND_CLOSEST(lsum, total); > - sq = sq * (lat - avg); > - *sq_sump += sq; > + if (unlikely(total == 1)) { > + *lavg = lat; > + *lstdev = 0; > + } else { > + avg = *lavg + div64_s64(lat - *lavg, total); > + stdev = *lstdev + (lat - *lavg)*(lat - avg); > + *lstdev = int_sqrt(div64_u64(stdev, total - 1)); In kernel space, won't it a little heavy to run the in_sqrt() every time when updating the latency ? @Jeff, any idea ? > + *lavg = avg; > + } > } > > void ceph_update_read_metrics(struct ceph_client_metric *m, > @@ -343,23 +352,18 @@ void ceph_update_read_metrics(struct ceph_client_metric *m, > unsigned int size, int rc) > { > ktime_t lat = ktime_sub(r_end, r_start); > - ktime_t total; > > if (unlikely(rc < 0 && rc != -ENOENT && rc != -ETIMEDOUT)) > return; > > spin_lock(&m->read_metric_lock); > - total = ++m->total_reads; > m->read_size_sum += size; > - m->read_latency_sum += lat; > METRIC_UPDATE_MIN_MAX(m->read_size_min, > m->read_size_max, > size); > - METRIC_UPDATE_MIN_MAX(m->read_latency_min, > - m->read_latency_max, > - lat); > - __update_stdev(total, m->read_latency_sum, > - &m->read_latency_sq_sum, lat); > + __update_latency(&m->total_reads, &m->read_latency_sum, > + &m->avg_read_latency, &m->read_latency_min, > + &m->read_latency_max, &m->read_latency_stdev, lat); > spin_unlock(&m->read_metric_lock); > } > > @@ -368,23 +372,18 @@ void ceph_update_write_metrics(struct ceph_client_metric *m, > unsigned int size, int rc) > { > ktime_t lat = ktime_sub(r_end, r_start); > - ktime_t total; > > if (unlikely(rc && rc != -ETIMEDOUT)) > return; > > spin_lock(&m->write_metric_lock); > - total = ++m->total_writes; > m->write_size_sum += size; > - m->write_latency_sum += lat; > METRIC_UPDATE_MIN_MAX(m->write_size_min, > m->write_size_max, > size); > - METRIC_UPDATE_MIN_MAX(m->write_latency_min, > - m->write_latency_max, > - lat); > - __update_stdev(total, m->write_latency_sum, > - &m->write_latency_sq_sum, lat); > + __update_latency(&m->total_writes, &m->write_latency_sum, > + &m->avg_write_latency, &m->write_latency_min, > + &m->write_latency_max, &m->write_latency_stdev, lat); > spin_unlock(&m->write_metric_lock); > } > > @@ -393,18 +392,13 @@ void ceph_update_metadata_metrics(struct ceph_client_metric *m, > int rc) > { > ktime_t lat = ktime_sub(r_end, r_start); > - ktime_t total; > > if (unlikely(rc && rc != -ENOENT)) > return; > > spin_lock(&m->metadata_metric_lock); > - total = ++m->total_metadatas; > - m->metadata_latency_sum += lat; > - METRIC_UPDATE_MIN_MAX(m->metadata_latency_min, > - m->metadata_latency_max, > - lat); > - __update_stdev(total, m->metadata_latency_sum, > - &m->metadata_latency_sq_sum, lat); > + __update_latency(&m->total_metadatas, &m->metadata_latency_sum, > + &m->avg_metadata_latency, &m->metadata_latency_min, > + &m->metadata_latency_max, &m->metadata_latency_stdev, lat); > spin_unlock(&m->metadata_metric_lock); > } > diff --git a/fs/ceph/metric.h b/fs/ceph/metric.h > index 103ed736f9d2..a5da21b8f8ed 100644 > --- a/fs/ceph/metric.h > +++ b/fs/ceph/metric.h > @@ -138,7 +138,8 @@ struct ceph_client_metric { > u64 read_size_min; > u64 read_size_max; > ktime_t read_latency_sum; > - ktime_t read_latency_sq_sum; > + ktime_t avg_read_latency; > + ktime_t read_latency_stdev; > ktime_t read_latency_min; > ktime_t read_latency_max; > > @@ -148,14 +149,16 @@ struct ceph_client_metric { > u64 write_size_min; > u64 write_size_max; > ktime_t write_latency_sum; > - ktime_t write_latency_sq_sum; > + ktime_t avg_write_latency; > + ktime_t write_latency_stdev; > ktime_t write_latency_min; > ktime_t write_latency_max; > > spinlock_t metadata_metric_lock; > u64 total_metadatas; > ktime_t metadata_latency_sum; > - ktime_t metadata_latency_sq_sum; > + ktime_t avg_metadata_latency; > + ktime_t metadata_latency_stdev; > ktime_t metadata_latency_min; > ktime_t metadata_latency_max; >