From nobody Fri Jul 24 22:51:46 2026 Received: from mail-pg1-f197.google.com (mail-pg1-f197.google.com [209.85.215.197]) (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 B60764399D2 for ; Wed, 22 Jul 2026 19:29:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.197 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784748594; cv=none; b=mpIKC0L6TGPBX5tBL73Gvd9kgTu9daEAIT1YRzFBUiOQTNB/rownsa3qpR3pNl7a+SNp2s57xa8mEmqaVYTeLRqlm7ROdM7XU8Ba9pkx4M2SeqJnxRkENcMpJK9zHp69H7z8cnUUC6IuNXoBRmVRr+yvls8cox0qtHo1C+BJUNI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784748594; c=relaxed/simple; bh=1Z2OfdCM1TMmz2cj6/tHDgbU0DqBU7MhOVEqR+0X/U4=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=hRMgyZQW0BLp8MRDGYcHwxmQ8UtScE37/ngmIEeP+wM7S/SaSpISs8Tyg+QLJHAh3uBzRpHjPCiIXiZk6E2XZD/0L3yZlgCAD3WQrp5TwiHBYks7m4GqqYamhSfD8lsVHC/D0HxHUeY36iLZcX0PPSm36tZPFf693PsgtJFFPMY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--pratmal.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=m4fX0acy; arc=none smtp.client-ip=209.85.215.197 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--pratmal.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="m4fX0acy" Received: by mail-pg1-f197.google.com with SMTP id 41be03b00d2f7-cb7d6ba548eso5038094a12.1 for ; Wed, 22 Jul 2026 12:29:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1784748582; x=1785353382; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:mime-version:date:from :to:cc:subject:date:message-id:reply-to:content-type; bh=KLXoX1ivD/mB2jEq+v6b3gqtvL3+A1iZJXkH/v2MOCg=; b=m4fX0acyJ9vC5lkieYNBTzz8nyWMd4sRdx3okaYcmd5qlHiQw4M+XTffMbGRBPgKxA x2j6TQJfXyAVwNFJuSAKgh2q7ZIie3x0eCOC21zW5d57xf26jAMUAx11aIDFx0fGUVDD S0w0opFBzpAL7tFRUWLo/yE26KQ5chhQ3QoEn05ZJCnKPOhi4sp+yjoxhd9GGckhCSEk AURcBguNkkR/deaJfLXr22xtxMwwPBFXpKwd7uIUVxz4PjZKP5SxIeEt738Uv921Zepb Q/wov+pAP0yGGJbHeQOd6ITeYNomXnfdo+417O5qnIUt0nygxwhmtq+PE9pjly3Pa4st gSPg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1784748582; x=1785353382; h=content-type:cc:to:from:subject:message-id:mime-version:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=KLXoX1ivD/mB2jEq+v6b3gqtvL3+A1iZJXkH/v2MOCg=; b=o7Vu/YjsnAAtiPBgauLdTzGc43Snw1UxV5NrRL4Xbl2GKLdIu+JS+k3wgfJjK6ys61 TBi2TTQhgPcxFavayqbdL7888+fJ/A/9dJnRZAJayLFDtAobhgstRDMsdN7brbaeNwLf zUCkEPI4D9Aa8O7VtMU/Ox2n/OOtwBRndHv5OluGszPJTPVP0Z9xzZCRtUAx87cQRd9k Nm+vCRemo4/bjlDzeBwHtA2QohTlrpRI+Dl1nMILkkt1z9u+Fh+KPB0+4+TwU9nVGqfL zBUuLS+lvyuY5OMqYSCtWl8c6S1CZDy2b+DdhOzr7ao0GGWj9MpZO0gWKHTUGDsZTEGL Ws0g== X-Forwarded-Encrypted: i=1; AHgh+RovGgcjNeCZs0vWe9aaNmho6SE3sPOvZXNEIPazLmbZWEk23OEpRwLKJKdpGL7DH5hs3AEmnw9+jvSWmUY=@vger.kernel.org X-Gm-Message-State: AOJu0Ywrcy8x+luymZRo0FxIxtCGKXcqK0l1+zQNNGzejCsWuCj1LpbE kmYO7jgCu+y/C6SLYDkIjOe9wpI62nL2z8ssNuLe9PD7ceMI9vHxtlk8mgr4I6RDicyplcg1TKi cSIugvx169w== X-Received: from dybsi15.prod.google.com ([2002:a05:7301:488f:b0:314:77c5:40b]) (user=pratmal job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:60c4:b0:3c0:9c1a:8936 with SMTP id adf61e73a8af0-3c3ad9ec55fmr27111478637.62.1784748582166; Wed, 22 Jul 2026 12:29:42 -0700 (PDT) Date: Wed, 22 Jul 2026 19:29:35 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.55.0.229.g6434b31f56-goog Message-ID: <20260722192935.1646848-1-pratmal@google.com> Subject: [PATCH v1] mm/page_reporting: Add page_reporting_delay_ms sysctl From: pratmal@google.com To: Anshuman Khandual , David Hildenbrand , Andrew Morton , Vlastimil Babka Cc: Greg Thelen , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Pratyush Mallick Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Pratyush Mallick Currently, the free page reporting daemon uses a hardcoded delay of (2 HZ) between reporting intervals. While this is a reasonable default, it lacks the flexibility to adapt to varying guest workloads. A low delay allows aggressive memory reclamation, returning unused pages to the hypervisor as quickly as possible. However, during spiky allocation/free churn, this immediate reporting can lead to a severe performance penalty (nested page faults) as the guest re-allocates memory that the hypervisor has just unmapped. In these scenarios, there is benefit from increasing the delay to batch free pages over a longer window, absorbing the churn without hypercall and re-fault overhead. This patch refactors the delay into a dynamically tunable sysctl, /proc/sys/vm/page_reporting_delay_ms, measured in milliseconds. The value defaults to 2000ms to precisely match the original (2 HZ) behavior. Signed-off-by: Pratyush Mallick --- v1: Fixed feedback from RFC. - Added lower and upper cap to sysctl value. - Reverted the reordering on page_reporting_delay_ms. - Droped the mod_delayed_work() change.=20 - https://lore.kernel.org/linux-mm/20260714171456.2350037-1-pratmal@googl= e.com/T/#u mm/page_reporting.c | 29 ++++++++++++++++++++++++++--- 1 file changed, 26 insertions(+), 3 deletions(-) diff --git a/mm/page_reporting.c b/mm/page_reporting.c index 942e84b6908a..4ca15afd06da 100644 --- a/mm/page_reporting.c +++ b/mm/page_reporting.c @@ -6,6 +6,7 @@ #include #include #include +#include #include =20 #include "page_reporting.h" @@ -47,7 +48,10 @@ MODULE_PARM_DESC(page_reporting_order, "Set page reporti= ng order"); */ EXPORT_SYMBOL_GPL(page_reporting_order); =20 -#define PAGE_REPORTING_DELAY (2 * HZ) +#define PAGE_REPORTING_DELAY_MS_MAX (10 * MSEC_PER_SEC) + +static unsigned int page_reporting_delay_ms =3D 2 * MSEC_PER_SEC; +static unsigned int page_reporting_delay_ms_max =3D PAGE_REPORTING_DELAY_M= S_MAX; static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly; =20 enum { @@ -56,6 +60,18 @@ enum { PAGE_REPORTING_ACTIVE }; =20 +static struct ctl_table page_reporting_sysctls[] =3D { + { + .procname =3D "page_reporting_delay_ms", + .data =3D &page_reporting_delay_ms, + .maxlen =3D sizeof(unsigned int), + .mode =3D 0644, + .proc_handler =3D proc_douintvec_minmax, + .extra1 =3D SYSCTL_ZERO, + .extra2 =3D &page_reporting_delay_ms_max, + }, +}; + /* request page reporting */ static void __page_reporting_request(struct page_reporting_dev_info *prdev) @@ -80,7 +96,7 @@ __page_reporting_request(struct page_reporting_dev_info *= prdev) * now we are limiting this to running no more than once every * couple of seconds. */ - schedule_delayed_work(&prdev->work, PAGE_REPORTING_DELAY); + schedule_delayed_work(&prdev->work, msecs_to_jiffies(page_reporting_delay= _ms)); } =20 /* notify prdev of free page reporting request */ @@ -340,7 +356,7 @@ static void page_reporting_process(struct work_struct *= work) */ state =3D atomic_cmpxchg(&prdev->state, state, PAGE_REPORTING_IDLE); if (state =3D=3D PAGE_REPORTING_REQUESTED) - schedule_delayed_work(&prdev->work, PAGE_REPORTING_DELAY); + schedule_delayed_work(&prdev->work, msecs_to_jiffies(page_reporting_dela= y_ms)); } =20 static DEFINE_MUTEX(page_reporting_mutex); @@ -416,3 +432,10 @@ void page_reporting_unregister(struct page_reporting_d= ev_info *prdev) mutex_unlock(&page_reporting_mutex); } EXPORT_SYMBOL_GPL(page_reporting_unregister); + +static int __init page_reporting_sysctl_init(void) +{ + register_sysctl_init("vm", page_reporting_sysctls); + return 0; +} +late_initcall(page_reporting_sysctl_init); --=20 2.55.0.229.g6434b31f56-goog