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=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 30C8CC47257 for ; Thu, 7 May 2020 08:29:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0C6472080D for ; Thu, 7 May 2020 08:29:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="BEAn+G0J" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725964AbgEGI3W (ORCPT ); Thu, 7 May 2020 04:29:22 -0400 Received: from smtp-fw-9101.amazon.com ([207.171.184.25]:32731 "EHLO smtp-fw-9101.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725819AbgEGI3V (ORCPT ); Thu, 7 May 2020 04:29:21 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1588840160; x=1620376160; h=from:to:cc:subject:date:message-id:in-reply-to: mime-version; bh=kQdkQWchIS0juDhlAm9sTzb/ZBV6GvvpTp81oVs0nKE=; b=BEAn+G0JIzpEBYAEcZNgB1Q5leuF89dE011gS/M02OB4CzkROfYmkE4E vpOA1i0Nq/W7xiAkVtuQRzim9MoY33TAPk4IoviU/l4U7OPCN8NoRezoD 8N+lCgAhxGGrh24lezDB4rm729RGZEB3pvrLRq6ayurHIjtDInom10NkX Q=; IronPort-SDR: aDOPUNuQuXya77sm5jk5VJKoaxwv11GiEZNQu/vbh/VIVfIMR81jxSQod3FfgthFPlRBQvsxsb 2h6C+r1o7xHg== X-IronPort-AV: E=Sophos;i="5.73,363,1583193600"; d="scan'208";a="33513335" Received: from sea32-co-svc-lb4-vlan3.sea.corp.amazon.com (HELO email-inbound-relay-1d-37fd6b3d.us-east-1.amazon.com) ([10.47.23.38]) by smtp-border-fw-out-9101.sea19.amazon.com with ESMTP; 07 May 2020 08:29:16 +0000 Received: from EX13MTAUEA002.ant.amazon.com (iad55-ws-svc-p15-lb9-vlan2.iad.amazon.com [10.40.159.162]) by email-inbound-relay-1d-37fd6b3d.us-east-1.amazon.com (Postfix) with ESMTPS id 4DA2C283958; Thu, 7 May 2020 08:29:14 +0000 (UTC) Received: from EX13D31EUA001.ant.amazon.com (10.43.165.15) by EX13MTAUEA002.ant.amazon.com (10.43.61.77) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Thu, 7 May 2020 08:29:13 +0000 Received: from u886c93fd17d25d.ant.amazon.com (10.43.161.175) by EX13D31EUA001.ant.amazon.com (10.43.165.15) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Thu, 7 May 2020 08:28:57 +0000 From: SeongJae Park To: , SeongJae Park CC: , SeongJae Park , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v10 06/16] mm/damon: Split regions into 4 subregions if possible Date: Thu, 7 May 2020 10:28:36 +0200 Message-ID: <20200507082836.32145-1-sjpark@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200505110815.10532-7-sjpark@amazon.com> (raw) MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.43.161.175] X-ClientProxiedBy: EX13D13UWB003.ant.amazon.com (10.43.161.233) To EX13D31EUA001.ant.amazon.com (10.43.165.15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 5 May 2020 13:08:05 +0200 SeongJae Park wrote: > From: SeongJae Park > > Suppose that there are a very wide and cold region and a hot region, and > both regions are identified by DAMON. And then, the middle small region > inside the very wide and cold region becomes hot. DAMON will not be > able to identify this new region because the adaptive regions adjustment > mechanism splits each region to only two subregions. > > This commit modifies the logic to split each region to 4 subregions if > possible so that such problematic region can eventually identified. As you can check with the 'Evaluations' section in the cover letter of this patchset, the extend of the slowdown DAMON's recording feature made to the target workload has doulbed (0.55% with v9, 1.02% with this patchset). It's still just a small number, but the worst case slowdown is 5.29%. It was only 1.88% before. I suspect this patch is the reason, as this is the only one major change we made after v9. For the reason, I would like to make this patch to split each region into 3 sub regions instead of 4 subregions. It will reduce the overhead a little bit while still allow the corner case regions be eventually detected. If you have other concerns or opinions, please let me know. Thanks, SeongJae Park > > Suggested-by: James Cameron > Signed-off-by: SeongJae Park > --- > mm/damon.c | 44 +++++++++++++++++++++++++++----------------- > 1 file changed, 27 insertions(+), 17 deletions(-) > > diff --git a/mm/damon.c b/mm/damon.c > index cec946197e13..342f905927a0 100644 > --- a/mm/damon.c > +++ b/mm/damon.c > @@ -650,26 +650,32 @@ static void damon_split_region_at(struct damon_ctx *ctx, > damon_insert_region(new, r, damon_next_region(r)); > } > > -/* Split every region in the given task into two randomly-sized regions */ > -static void damon_split_regions_of(struct damon_ctx *ctx, struct damon_task *t) > +/* Split every region in the given task into 'nr_subs' regions */ > +static void damon_split_regions_of(struct damon_ctx *ctx, > + struct damon_task *t, int nr_subs) > { > struct damon_region *r, *next; > - unsigned long sz_orig_region, sz_left_region; > + unsigned long sz_region, sz_sub = 0; > + int i; > > damon_for_each_region_safe(r, next, t) { > - sz_orig_region = r->vm_end - r->vm_start; > - > - /* > - * Randomly select size of left sub-region to be at least > - * 10 percent and at most 90% of original region > - */ > - sz_left_region = ALIGN_DOWN(damon_rand(1, 10) * sz_orig_region > - / 10, MIN_REGION); > - /* Do not allow blank region */ > - if (sz_left_region == 0 || sz_left_region >= sz_orig_region) > - continue; > - > - damon_split_region_at(ctx, r, sz_left_region); > + sz_region = r->vm_end - r->vm_start; > + > + for (i = 0; i < nr_subs - 1 && > + sz_region > 2 * MIN_REGION; i++) { > + /* > + * Randomly select size of left sub-region to be at > + * least 10 percent and at most 90% of original region > + */ > + sz_sub = ALIGN_DOWN(damon_rand(1, 10) * > + sz_region / 10, MIN_REGION); > + /* Do not allow blank region */ > + if (sz_sub == 0 || sz_sub >= sz_region) > + continue; > + > + damon_split_region_at(ctx, r, sz_sub); > + sz_region = sz_sub; > + } > } > } > > @@ -687,14 +693,18 @@ static void kdamond_split_regions(struct damon_ctx *ctx) > { > struct damon_task *t; > unsigned int nr_regions = 0; > + int nr_subregions = 2; > > damon_for_each_task(ctx, t) > nr_regions += nr_damon_regions(t); > if (nr_regions > ctx->max_nr_regions / 2) > return; > > + if (nr_regions < ctx->max_nr_regions / 4) > + nr_subregions = 4; > + > damon_for_each_task(ctx, t) > - damon_split_regions_of(ctx, t); > + damon_split_regions_of(ctx, t, nr_subregions); > } > > /* > -- > 2.17.1 >