From nobody Fri Dec 19 17:00:23 2025 Received: from mail-yx1-f52.google.com (mail-yx1-f52.google.com [74.125.224.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B04922C21EA for ; Mon, 13 Oct 2025 19:08:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.224.52 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760382499; cv=none; b=UrnBTUvhSk4cyNoJaGwx76Z14peAw0vvdXhWswEY7Oioi8Ih7aXSTd8g34BdIFNYwByv6W7WC5EFzl60nwdAPCUwNe6LL5gu2V3vIHzKX7EiLtzPNIhSsF6Qp9TjKY+Yt1KqKWYFL0bb+sIvwBQeplm5ul2VD6IZRg9R3KBy1B8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760382499; c=relaxed/simple; bh=bCS44l/LvBBitJnnk4ob4XEeLl5p3PQtQuAfvJHhxEs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Gp3TIV71ng90rGSjUeVjxLe7YsOH9Jefx9sn6JDAp+nuhQp+5hVtg3T+cm9FqQu6M6URUZV+2mHnbaTrYDiqiVyP0NhTTgzwgcnz85WVH1PmSvJhqiXsJ0Yit4DaJm/LUhqPncKPprvJ5IPcS5e67UsEvuGqzuzFVtAPUfqS0y0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Y5zI4YP+; arc=none smtp.client-ip=74.125.224.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Y5zI4YP+" Received: by mail-yx1-f52.google.com with SMTP id 956f58d0204a3-6361a421b67so4702260d50.2 for ; Mon, 13 Oct 2025 12:08:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1760382494; x=1760987294; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=DaKsUlhHVYzGr/qaa9OrQYufYtYEbalh3sXBUEUgogU=; b=Y5zI4YP+0m4h2ptSPJA4qAoC6Yd2p+vTLVRvOnji6K9RY8NiyxbRnAYb8i4V9DEfL2 ucI3B6/zf/R0AX4J2D77pVGZyHrn8hEfK2T9Ar2dDsEoG/g9STa1FIaEwVBYIbieBVrM +jeiqoXvRdyqoRfdhKz1Sq49t3fcL1FdDHUZ0qua4ev25vialg9afjAk72K3ahVBGFc0 5M0F+dXzWDI3UJM9SCzAykHyXdRaI10yV/vv/ZYWldXfmLaUsLxODtAp65fwUNMcWhT/ gJn9IPPV3W7/zWpgMDDcTeFiyqRXeIeaTbE2pXX+/stJ/uC86OK+RcaeftA89AHKGuFy 9iQw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1760382494; x=1760987294; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=DaKsUlhHVYzGr/qaa9OrQYufYtYEbalh3sXBUEUgogU=; b=JvMHUcJFxPbnkquTPnHT5xdLwYZSW8wVLPdzIkPZvs5xLX9pX4BCoF46oxBxvbp7G9 XaqczXFDziHpK9oG6gEk9oFCGMqvnBu+L5s1XfEEVtQiEv1fZj4/vie+lPJElzmnzA5t Dq1YV10NioY2e7fCO7vxGDIVhGJs4JPj2B6AxMFlbYEwUwDIHFjheB5980RqNpYxObb9 0ZHjJS5GIgMvVq9tifGPubX3OJrLVMwAMExp7yYwsj1jX6OSR1sztwaTN07BdG/1t2k6 SfSXEjwolhp7vojKSf4kUQdj1S28xAOhNktuWnG3QM0RGvOsKxaHKDpevN7EhtxVrc2m sPZA== X-Forwarded-Encrypted: i=1; AJvYcCXUVcXvArv0MGfpR9ePhCNDKhg/Lsv/9u+Am0HENnJDQek7880/sjlCcU85gU1/jOs+WD5AxhiZ1qi8nOw=@vger.kernel.org X-Gm-Message-State: AOJu0YzEHsX41eR1GZJYcSb05wlydmerSssjtNPAjcxPkpOUlndyZKyP dc3zrqLcrYWQOHhRvnomCEAGiNSKN/5zHn+tAM0ngvzsOsUrOY3e8ECc X-Gm-Gg: ASbGnctHky41LW1T5E5Sihg62aWcbiiDSU5VE8HU+YoxsuZdk2S/ZsvQdk8iuWgGh4i BgEujIuDm2dMzAWMF8J7V8PI34/dssRiJ+cjd+zo1i8eJrWXUs9zV02oam1+WbtNXXx6eU6D0Wn KL3QwnK3i9gaFgVFKNCUzhj9uFz4tSsc7s0kqine6Uu8ObR7h7VGMf50F5SjqCJNlzLmENYrlTA Sw1mPToxs9igW05I3luPlbgjzPi6Ibtc/mMiyMlltZR6+WSdppAJo2Qf5IBU/I9PI3wSse0Vvdw 2/SXzv6NeQmU7PMlcCotR2WlmBKOHDfPh1hEM6WXi/2/DxtMa+YVLVBGNbH7F7yvPtlbNwaajBq MxZ6KmAg93Q/91He6jAdxLH92ebXM6xLUXHJIAd9XNK3H05XlL0tTrVmzYAeFhh/CU2KPF1VrUp C9nI/mHXJslqM+Ew3tsSA= X-Google-Smtp-Source: AGHT+IHCF7ulcRqtzOcwLOSypYkVBjLtTayORGayA5ndYRP3Xnuskyn2V4s/3SPUaOLMHR0F/AXzvA== X-Received: by 2002:a05:690e:164f:b0:63c:db25:6406 with SMTP id 956f58d0204a3-63cdb2584d8mr10560890d50.42.1760382494512; Mon, 13 Oct 2025 12:08:14 -0700 (PDT) Received: from localhost ([2a03:2880:25ff:73::]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-63cd9524284sm4219891d50.10.2025.10.13.12.08.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Oct 2025 12:08:14 -0700 (PDT) From: Joshua Hahn To: Andrew Morton Cc: Chris Mason , Kiryl Shutsemau , "Liam R. Howlett" , Brendan Jackman , David Hildenbrand , Johannes Weiner , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , Zi Yan , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v4 1/3] mm/page_alloc/vmstat: Simplify refresh_cpu_vm_stats change detection Date: Mon, 13 Oct 2025 12:08:09 -0700 Message-ID: <20251013190812.787205-2-joshua.hahnjy@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251013190812.787205-1-joshua.hahnjy@gmail.com> References: <20251013190812.787205-1-joshua.hahnjy@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Currently, refresh_cpu_vm_stats returns an int, indicating how many changes were made during its updates. Using this information, callers like vmstat_update can heuristically determine if more work will be done in the future. However, all of refresh_cpu_vm_stats's callers either (a) ignore the result, only caring about performing the updates, or (b) only care about whether changes were made, but not *how many* changes were made. Simplify the code by returning a bool instead to indicate if updates were made. In addition, simplify fold_diff and decay_pcp_high to return a bool for the same reason. Reviewed-by: Vlastimil Babka Reviewed-by: SeongJae Park Signed-off-by: Joshua Hahn --- include/linux/gfp.h | 2 +- mm/page_alloc.c | 8 ++++---- mm/vmstat.c | 28 +++++++++++++++------------- 3 files changed, 20 insertions(+), 18 deletions(-) diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 0ceb4e09306c..f46b066c7661 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -386,7 +386,7 @@ extern void free_pages(unsigned long addr, unsigned int= order); #define free_page(addr) free_pages((addr), 0) =20 void page_alloc_init_cpuhp(void); -int decay_pcp_high(struct zone *zone, struct per_cpu_pages *pcp); +bool decay_pcp_high(struct zone *zone, struct per_cpu_pages *pcp); void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp); void drain_all_pages(struct zone *zone); void drain_local_pages(struct zone *zone); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 600d9e981c23..bbc3282fdffc 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2557,10 +2557,10 @@ static int rmqueue_bulk(struct zone *zone, unsigned= int order, * Called from the vmstat counter updater to decay the PCP high. * Return whether there are addition works to do. */ -int decay_pcp_high(struct zone *zone, struct per_cpu_pages *pcp) +bool decay_pcp_high(struct zone *zone, struct per_cpu_pages *pcp) { int high_min, to_drain, batch; - int todo =3D 0; + bool todo =3D false; =20 high_min =3D READ_ONCE(pcp->high_min); batch =3D READ_ONCE(pcp->batch); @@ -2573,7 +2573,7 @@ int decay_pcp_high(struct zone *zone, struct per_cpu_= pages *pcp) pcp->high =3D max3(pcp->count - (batch << CONFIG_PCP_BATCH_SCALE_MAX), pcp->high - (pcp->high >> 3), high_min); if (pcp->high > high_min) - todo++; + todo =3D true; } =20 to_drain =3D pcp->count - pcp->high; @@ -2581,7 +2581,7 @@ int decay_pcp_high(struct zone *zone, struct per_cpu_= pages *pcp) spin_lock(&pcp->lock); free_pcppages_bulk(zone, to_drain, pcp, 0); spin_unlock(&pcp->lock); - todo++; + todo =3D true; } =20 return todo; diff --git a/mm/vmstat.c b/mm/vmstat.c index bb09c032eecf..98855f31294d 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -771,25 +771,25 @@ EXPORT_SYMBOL(dec_node_page_state); =20 /* * Fold a differential into the global counters. - * Returns the number of counters updated. + * Returns whether counters were updated. */ static int fold_diff(int *zone_diff, int *node_diff) { int i; - int changes =3D 0; + bool changed =3D false; =20 for (i =3D 0; i < NR_VM_ZONE_STAT_ITEMS; i++) if (zone_diff[i]) { atomic_long_add(zone_diff[i], &vm_zone_stat[i]); - changes++; + changed =3D true; } =20 for (i =3D 0; i < NR_VM_NODE_STAT_ITEMS; i++) if (node_diff[i]) { atomic_long_add(node_diff[i], &vm_node_stat[i]); - changes++; + changed =3D true; } - return changes; + return changed; } =20 /* @@ -806,16 +806,16 @@ static int fold_diff(int *zone_diff, int *node_diff) * with the global counters. These could cause remote node cache line * bouncing and will have to be only done when necessary. * - * The function returns the number of global counters updated. + * The function returns whether global counters were updated. */ -static int refresh_cpu_vm_stats(bool do_pagesets) +static bool refresh_cpu_vm_stats(bool do_pagesets) { struct pglist_data *pgdat; struct zone *zone; int i; int global_zone_diff[NR_VM_ZONE_STAT_ITEMS] =3D { 0, }; int global_node_diff[NR_VM_NODE_STAT_ITEMS] =3D { 0, }; - int changes =3D 0; + bool changed =3D false; =20 for_each_populated_zone(zone) { struct per_cpu_zonestat __percpu *pzstats =3D zone->per_cpu_zonestats; @@ -839,7 +839,8 @@ static int refresh_cpu_vm_stats(bool do_pagesets) if (do_pagesets) { cond_resched(); =20 - changes +=3D decay_pcp_high(zone, this_cpu_ptr(pcp)); + if (decay_pcp_high(zone, this_cpu_ptr(pcp))) + changed =3D true; #ifdef CONFIG_NUMA /* * Deal with draining the remote pageset of this @@ -861,13 +862,13 @@ static int refresh_cpu_vm_stats(bool do_pagesets) } =20 if (__this_cpu_dec_return(pcp->expire)) { - changes++; + changed =3D true; continue; } =20 if (__this_cpu_read(pcp->count)) { drain_zone_pages(zone, this_cpu_ptr(pcp)); - changes++; + changed =3D true; } #endif } @@ -887,8 +888,9 @@ static int refresh_cpu_vm_stats(bool do_pagesets) } } =20 - changes +=3D fold_diff(global_zone_diff, global_node_diff); - return changes; + if (fold_diff(global_zone_diff, global_node_diff)) + changed =3D true; + return changed; } =20 /* --=20 2.47.3