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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,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 E2458C76186 for ; Wed, 24 Jul 2019 04:01:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BCB5A20823 for ; Wed, 24 Jul 2019 04:01:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725917AbfGXEBX (ORCPT ); Wed, 24 Jul 2019 00:01:23 -0400 Received: from mail-ot1-f66.google.com ([209.85.210.66]:33747 "EHLO mail-ot1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725810AbfGXEBX (ORCPT ); Wed, 24 Jul 2019 00:01:23 -0400 Received: by mail-ot1-f66.google.com with SMTP id q20so46368150otl.0; Tue, 23 Jul 2019 21:01:22 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=bP783P8vHL5hvGQlKfl7m6itu22DJvCAUy0AE7ISvs8=; b=qPCplhanET8r4/AEG8Z1Oez4ly5YfbYj4GLsdIxHRcXyBhdG7qQv5tKVda6VGFN0wM LJaApJvBC6njyvQQ26dUfFIGfAa4vXbHJr/SUhX7M5c+FMhApEdRPvqja9R/m6LxFDm+ yKVg2f1U/YJYDx7MEYh/VGa7M5ltkg+9Di8c0Vajc17XVxihzTho2liR5JBp+FixCxbR WAeCZZtU8kBlKjfQrXum+zoAgO0yG5Qad+JbgaQKSWpcn0k6ij1L/NNuPAk6Os1CTRjl qeHQDP5fNQyzjlhO/y5TArPmVp7XeBX7a0LuwRLHNclhdyVLcv2nqixDMLS2jqsJNDq8 ZJDA== X-Gm-Message-State: APjAAAUXPEUH2/O4zOb6jE9CY/uFmx5lhEztqsAumI/++guoPL29vbhO u4T60dvV0g6vIXdk3rUTsbOi2qCteQU= X-Google-Smtp-Source: APXvYqzjQnT/DOSjKiboa1+pO2X26nHpVVkku+OAM/CDAP5PrqN95J4LDbJVoBS0zVwaEYQxeDcYCQ== X-Received: by 2002:a9d:5ed:: with SMTP id 100mr6248811otd.105.1563940881828; Tue, 23 Jul 2019 21:01:21 -0700 (PDT) Received: from sultan-box.localdomain ([192.111.140.132]) by smtp.gmail.com with ESMTPSA id v65sm15464278oig.51.2019.07.23.21.01.20 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 23 Jul 2019 21:01:21 -0700 (PDT) Date: Tue, 23 Jul 2019 22:01:18 -0600 From: Sultan Alsawaf To: Andreas Dilger Cc: Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mbcache: Speed up cache entry creation Message-ID: <20190724040118.GA31214@sultan-box.localdomain> References: <20190723053549.14465-1-sultan@kerneltoast.com> <5EDDA127-031C-4F16-9B9B-8DBC94C7E471@dilger.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5EDDA127-031C-4F16-9B9B-8DBC94C7E471@dilger.ca> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 23, 2019 at 10:56:05AM -0600, Andreas Dilger wrote: > Do you have any kind of performance metrics that show this is an actual > improvement in performance? This would be either macro-level benchmarks > (e.g. fio, but this seems unlikely to show any benefit), or micro-level > measurements (e.g. flame graph) that show a net reduction in CPU cycles, > lock contention, etc. in this part of the code. Hi Andreas, Here are some basic micro-benchmark results: Before: [ 3.162896] mb_cache_entry_create: AVG cycles: 75 [ 3.054701] mb_cache_entry_create: AVG cycles: 78 [ 3.152321] mb_cache_entry_create: AVG cycles: 77 After: [ 3.043380] mb_cache_entry_create: AVG cycles: 68 [ 3.194321] mb_cache_entry_create: AVG cycles: 71 [ 3.038100] mb_cache_entry_create: AVG cycles: 69 The performance difference is probably more drastic when free memory is low, since an unnecessary call to kmem_cache_alloc() can result in a long wait for pages to be freed. The micro-benchmark code is attached. Thanks, Sultan --- diff --git a/fs/mbcache.c b/fs/mbcache.c index 289f3664061e..e0f22ff8fab8 100644 --- a/fs/mbcache.c +++ b/fs/mbcache.c @@ -82,7 +82,7 @@ static inline struct mb_bucket *mb_cache_entry_bucket(struct mb_cache *cache, * -EBUSY if entry with the same key and value already exists in cache. * Otherwise 0 is returned. */ -int mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key, +static int __mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key, u64 value, bool reusable) { struct mb_cache_entry *entry, *dup; @@ -148,6 +148,29 @@ int mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key, return 0; } + +int mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key, + u64 value, bool reusable) +{ + static unsigned long count, sum; + static DEFINE_MUTEX(lock); + volatile cycles_t start, delta; + int ret; + + mutex_lock(&lock); + local_irq_disable(); + start = get_cycles(); + ret = __mb_cache_entry_create(cache, mask, key, value, reusable); + delta = get_cycles() - start; + local_irq_enable(); + + sum += delta; + if (++count == 1000) + printk("%s: AVG cycles: %lu\n", __func__, sum / count); + mutex_unlock(&lock); + + return ret; +} EXPORT_SYMBOL(mb_cache_entry_create); void __mb_cache_entry_free(struct mb_cache_entry *entry)