From nobody Fri Feb 13 12:30:07 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AF9FAE8181D for ; Tue, 26 Sep 2023 06:09:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233754AbjIZGJy (ORCPT ); Tue, 26 Sep 2023 02:09:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45118 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233760AbjIZGJq (ORCPT ); Tue, 26 Sep 2023 02:09:46 -0400 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 02DA5FF for ; Mon, 25 Sep 2023 23:09:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1695708578; x=1727244578; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=DeMClJs3Mthv/xHdoFt3z4ewOtGnsu4v3P02NwqV+vA=; b=VOBmpBkdzmmxLP1p7/AsfxqbnDSe427lVvh7D3GTe6lBuSZs+wlZ5tt1 opVjduS2p950Kr/MPJgOj12Muy2YH+AdliJuI3zUtyFzF5xyIlQw3Tvu9 7SVwm2sw5MF69YxZlhmoUSFt0uXZbbDFFgcXO2wFl9jfxmHt85GK6hVHt k/9Cx18eIAPa0SlDH/7byTozJJ0nTA4vOrPetiAMbaOozN3ihWTK4IA7C Nrd2qjK4i5S1Uz00vXkuVtvy1oosSOGqDMUKhR+1Bx2OVNjKpq2FyvrTb 5aOA6fazUjo/o6dQixIZYM2j336UOzaDvY7A74Ym93gRbj6pKNjW+28BJ A==; X-IronPort-AV: E=McAfee;i="6600,9927,10843"; a="447991309" X-IronPort-AV: E=Sophos;i="6.03,177,1694761200"; d="scan'208";a="447991309" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Sep 2023 23:09:38 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10843"; a="892075877" X-IronPort-AV: E=Sophos;i="6.03,177,1694761200"; d="scan'208";a="892075877" Received: from aozhu-mobl.ccr.corp.intel.com (HELO yhuang6-mobl2.ccr.corp.intel.com) ([10.255.31.94]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Sep 2023 23:08:30 -0700 From: Huang Ying To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Arjan Van De Ven , Huang Ying , Mel Gorman , Vlastimil Babka , David Hildenbrand , Johannes Weiner , Dave Hansen , Michal Hocko , Pavel Tatashin , Matthew Wilcox , Christoph Lameter Subject: [PATCH -V2 03/10] mm, pcp: reduce lock contention for draining high-order pages Date: Tue, 26 Sep 2023 14:09:04 +0800 Message-Id: <20230926060911.266511-4-ying.huang@intel.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230926060911.266511-1-ying.huang@intel.com> References: <20230926060911.266511-1-ying.huang@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" In commit f26b3fa04611 ("mm/page_alloc: limit number of high-order pages on PCP during bulk free"), the PCP (Per-CPU Pageset) will be drained when PCP is mostly used for high-order pages freeing to improve the cache-hot pages reusing between page allocating and freeing CPUs. On system with small per-CPU data cache, pages shouldn't be cached before draining to guarantee cache-hot. But on a system with large per-CPU data cache, more pages can be cached before draining to reduce zone lock contention. So, in this patch, instead of draining without any caching, "batch" pages will be cached in PCP before draining if the per-CPU data cache size is more than "4 * batch". On a 2-socket Intel server with 128 logical CPU, with the patch, the network bandwidth of the UNIX (AF_UNIX) test case of lmbench test suite with 16-pair processes increase 72.2%. The cycles% of the spinlock contention (mostly for zone lock) decreases from 45.8% to 21.2%. The number of PCP draining for high order pages freeing (free_high) decreases 89.8%. The cache miss rate keeps 0.3%. Signed-off-by: "Huang, Ying" Cc: Andrew Morton Cc: Mel Gorman Cc: Vlastimil Babka Cc: David Hildenbrand Cc: Johannes Weiner Cc: Dave Hansen Cc: Michal Hocko Cc: Pavel Tatashin Cc: Matthew Wilcox Cc: Christoph Lameter --- drivers/base/cacheinfo.c | 2 ++ include/linux/gfp.h | 1 + include/linux/mmzone.h | 1 + mm/page_alloc.c | 37 ++++++++++++++++++++++++++++++++++++- 4 files changed, 40 insertions(+), 1 deletion(-) diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c index 3e8951a3fbab..a55b2f83958b 100644 --- a/drivers/base/cacheinfo.c +++ b/drivers/base/cacheinfo.c @@ -943,6 +943,7 @@ static int cacheinfo_cpu_online(unsigned int cpu) if (rc) goto err; update_data_cache_size(true, cpu); + setup_pcp_cacheinfo(); return 0; err: free_cache_attributes(cpu); @@ -956,6 +957,7 @@ static int cacheinfo_cpu_pre_down(unsigned int cpu) =20 free_cache_attributes(cpu); update_data_cache_size(false, cpu); + setup_pcp_cacheinfo(); return 0; } =20 diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 665f06675c83..665edc11fb9f 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -325,6 +325,7 @@ void drain_all_pages(struct zone *zone); void drain_local_pages(struct zone *zone); =20 void page_alloc_init_late(void); +void setup_pcp_cacheinfo(void); =20 /* * gfp_allowed_mask is set to GFP_BOOT_MASK during early boot to restrict = what diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 64d5ed2bb724..4132e7490b49 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -677,6 +677,7 @@ enum zone_watermarks { #define wmark_pages(z, i) (z->_watermark[i] + z->watermark_boost) =20 #define PCPF_PREV_FREE_HIGH_ORDER 0x01 +#define PCPF_FREE_HIGH_BATCH 0x02 =20 struct per_cpu_pages { spinlock_t lock; /* Protects lists field */ diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 295e61f0c49d..e97814985710 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -52,6 +52,7 @@ #include #include #include +#include #include #include "internal.h" #include "shuffle.h" @@ -2385,7 +2386,9 @@ static void free_unref_page_commit(struct zone *zone,= struct per_cpu_pages *pcp, */ if (order && order <=3D PAGE_ALLOC_COSTLY_ORDER) { free_high =3D (pcp->free_factor && - (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER)); + (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) && + (!(pcp->flags & PCPF_FREE_HIGH_BATCH) || + pcp->count >=3D READ_ONCE(pcp->batch))); pcp->flags |=3D PCPF_PREV_FREE_HIGH_ORDER; } else if (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) { pcp->flags &=3D ~PCPF_PREV_FREE_HIGH_ORDER; @@ -5418,6 +5421,38 @@ static void zone_pcp_update(struct zone *zone, int c= pu_online) mutex_unlock(&pcp_batch_high_lock); } =20 +static void zone_pcp_update_cacheinfo(struct zone *zone) +{ + int cpu; + struct per_cpu_pages *pcp; + struct cpu_cacheinfo *cci; + + for_each_online_cpu(cpu) { + pcp =3D per_cpu_ptr(zone->per_cpu_pageset, cpu); + cci =3D get_cpu_cacheinfo(cpu); + /* + * If per-CPU data cache is large enough, up to + * "batch" high-order pages can be cached in PCP for + * consecutive freeing. This can reduce zone lock + * contention without hurting cache-hot pages sharing. + */ + spin_lock(&pcp->lock); + if ((cci->size_data >> PAGE_SHIFT) > 4 * pcp->batch) + pcp->flags |=3D PCPF_FREE_HIGH_BATCH; + else + pcp->flags &=3D ~PCPF_FREE_HIGH_BATCH; + spin_unlock(&pcp->lock); + } +} + +void setup_pcp_cacheinfo(void) +{ + struct zone *zone; + + for_each_populated_zone(zone) + zone_pcp_update_cacheinfo(zone); +} + /* * Allocate per cpu pagesets and initialize them. * Before this call only boot pagesets were available. --=20 2.39.2