From nobody Sat Oct 4 19:15:54 2025 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1E4002FE583; Wed, 13 Aug 2025 14:57:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755097081; cv=none; b=X2SJh83KFt3yBu8uKs72iDb1MZzmSJUcosCv8ilJkIbrXQOR3+SLL1R1SJzkcQxlk05Y+aDCEcfCQYWQ145ndTvJnCq7ygUpIaNeTNcvKv03m3mVHt5o8eo4q3kO6BH7/XwvUMDILz+B6xSzfMgtAROuHeQ3sfKXrIdGw8RW1fw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755097081; c=relaxed/simple; bh=I2IWMtoFl5keplxHSLJtItCr7nzwxIzEBEtLkTKoLhc=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=k3+e1CZGAVyTv13iG1aEhHSGGlzuskxEq0oP/gQw4smr2B8iZInxLFSw9GEwUmOdBpalRd5Cuz2MrN79mOL5EAQyShnXkRo1f/V3duuoN63zDWDxmb7fKG+QR5nNJMWoVOIyzOn4TAQ+jVauvuEET5tfwqKjUMpMqSsBGrhtPyI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=I3u5d4XV; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=BPoRvRPO; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="I3u5d4XV"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="BPoRvRPO" From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1755097076; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type; bh=LK0fse9piQMDsNEawnHa17CJtTGb1+S7lgjGFKtF0tc=; b=I3u5d4XVCbp9sJAiqzUxxnN8jogvVz330rmXlvPc4EIs9kOtcf3Mj8uSjIxg1fRTrbwecl TMhr5g/y26FthJ72gtEwrU4u6dRhFhPmFvZEuofvCR2S34BZx0XaO71/N7GdY3Si7KdKQH rRll7+2m0QLENvmItC7EZWe2cT/j1aiQ6gFxiMmD1YFmNrWvCltHacGpPwgXO0KxHf97IA wynDG8BsBzIwHDNhNCP7ES+PQV4KCfRw73ymS0am7NjJRjrB20+Ua//P3TMmK8Xia9SQNY /xlAJETgVH3RXlHC8LNh3uYz9R0F8OR6g5b5Bwckh4QWwwVqXxslL1lpiee33Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1755097076; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type; bh=LK0fse9piQMDsNEawnHa17CJtTGb1+S7lgjGFKtF0tc=; b=BPoRvRPOD4TmXUa3bcE7pvCwZh4VhvmvEvaz/Zod57Zu5kVP4MdtmFgc2nUPCdQq1DcUDv jEKTQlAF2z04ZwDw== To: linux-mm@kvack.org Cc: LKML , Peter Zijlstra , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , cgroups@vger.kernel.org, Andrew Morton Subject: [PATCH] memcg: Optimize exit to user space Date: Wed, 13 Aug 2025 16:57:55 +0200 Message-ID: <87tt2b6zgs.ffs@tglx> 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" memcg uses TIF_NOTIFY_RESUME to handle reclaiming on exit to user space. TIF_NOTIFY_RESUME is a multiplexing TIF bit, which is utilized by other entities as well. This results in a unconditional mem_cgroup_handle_over_high() call for every invocation of resume_user_mode_work(), which is a pointless exercise as most of the time there is no reclaim work to do. Especially since RSEQ is used by glibc, TIF_NOTIFY_RESUME is raised quite frequently and the empty calls show up in exit path profiling. Optimize this by doing a quick check of the reclaim condition before invoking it. Signed-off-by: Thomas Gleixner Cc: Johannes Weiner Cc: Michal Hocko Cc: Roman Gushchin Cc: Shakeel Butt Cc: Muchun Song Cc: Andrew Morton Acked-by: Johannes Weiner Acked-by: Shakeel Butt Reviewed-by: Roman Gushchin --- include/linux/memcontrol.h | 8 +++++++- mm/memcontrol.c | 4 ++-- 2 files changed, 9 insertions(+), 3 deletions(-) --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -900,7 +900,13 @@ unsigned long mem_cgroup_get_zone_lru_si return READ_ONCE(mz->lru_zone_size[zone_idx][lru]); } =20 -void mem_cgroup_handle_over_high(gfp_t gfp_mask); +void __mem_cgroup_handle_over_high(gfp_t gfp_mask); + +static inline void mem_cgroup_handle_over_high(gfp_t gfp_mask) +{ + if (unlikely(current->memcg_nr_pages_over_high)) + __mem_cgroup_handle_over_high(gfp_mask); +} =20 unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg); =20 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2203,7 +2203,7 @@ static unsigned long calculate_high_dela * try_charge() (context permitting), as well as from the userland * return path where reclaim is always able to block. */ -void mem_cgroup_handle_over_high(gfp_t gfp_mask) +void __mem_cgroup_handle_over_high(gfp_t gfp_mask) { unsigned long penalty_jiffies; unsigned long pflags; @@ -2486,7 +2486,7 @@ static int try_charge_memcg(struct mem_c if (current->memcg_nr_pages_over_high > MEMCG_CHARGE_BATCH && !(current->flags & PF_MEMALLOC) && gfpflags_allow_blocking(gfp_mask)) - mem_cgroup_handle_over_high(gfp_mask); + __mem_cgroup_handle_over_high(gfp_mask); return 0; }