From nobody Sat Feb 7 11:31:33 2026 Received: from out-178.mta0.migadu.com (out-178.mta0.migadu.com [91.218.175.178]) (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 6AA975A4D5; Fri, 9 Aug 2024 17:26:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.178 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723224402; cv=none; b=l/AFNUauSzb/TPy16brxJQpu4aBuKfnC3Gw/jqnz6UZsoJFxnfFLjxl7O8ZoR1isqn1Us5cc3mrTx0wWlfU0Yli1Juky/TFLV0jOOBLZ9z+v/oY7jgB5CQNxRAiHXuOUp2j4KtzqxAypYrTDeGT1AvMmH05g+ON/umwjSXhWUvw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723224402; c=relaxed/simple; bh=Y9AqZWGd8ifzezhtCypSmtKu6I9N0YJ4qBpfG6DjUMw=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=WCHidY4Nrbngn3IC2+tlLHbid1aYCJZ1bNkDmRwyauW+KcIAXhyCEbFkHQvmM88XqHCWUykgWbXyQMkXXn5UBOze9E8rKPgj2JvqKLb/L+a3gx4NnBaARr5eDFpWEUV5eZo7EuwXWQInrjaA3QviMHK4uGwBMZi6zt9mLK7XH/A= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=G20TQ2+p; arc=none smtp.client-ip=91.218.175.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="G20TQ2+p" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1723224396; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=4iM0sefc3D7BN1ZfyJuESRluKUUBy69Kzbm9ZY4Fy3M=; b=G20TQ2+pPsPGtYkq8R7r38M9mMpyGGn6n276jn3JI1ZBVxvkOU5QGK9WvKp0ioHSZ+boXo Sv7Gu5thZjvb35Jh4i2klPZasx1mouiXlypVYRheOY9kUwUC/vGw7qs1xTDlKYswOxyHLT zTFBdkng29rTwZaGOhIMbkqBm5ZR5UE= From: Shakeel Butt To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Meta kernel team , cgroups@vger.kernel.org, Matthew Wilcox Subject: [PATCH] memcg: replace memcg ID idr with xarray Date: Fri, 9 Aug 2024 10:26:18 -0700 Message-ID: <20240809172618.2946790-1-shakeel.butt@linux.dev> 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 X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" At the moment memcg IDs are managed through IDR which requires external synchronization mechanisms and makes the allocation code a bit awkward. Let's switch to xarray and make the code simpler. Suggested-by: Matthew Wilcox Signed-off-by: Shakeel Butt Acked-by: Johannes Weiner Acked-by: Michal Hocko Reviewed-by: Matthew Wilcox (Oracle) Reviewed-by: Muchun Song Reviewed-by: Roman Gushchin --- mm/memcontrol.c | 34 +++++++--------------------------- 1 file changed, 7 insertions(+), 27 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e1ffd2950393..b8e6b98485c6 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3363,29 +3363,12 @@ static void memcg_wb_domain_size_changed(struct mem= _cgroup *memcg) */ =20 #define MEM_CGROUP_ID_MAX ((1UL << MEM_CGROUP_ID_SHIFT) - 1) -static DEFINE_IDR(mem_cgroup_idr); -static DEFINE_SPINLOCK(memcg_idr_lock); - -static int mem_cgroup_alloc_id(void) -{ - int ret; - - idr_preload(GFP_KERNEL); - spin_lock(&memcg_idr_lock); - ret =3D idr_alloc(&mem_cgroup_idr, NULL, 1, MEM_CGROUP_ID_MAX + 1, - GFP_NOWAIT); - spin_unlock(&memcg_idr_lock); - idr_preload_end(); - return ret; -} +static DEFINE_XARRAY_ALLOC1(mem_cgroup_ids); =20 static void mem_cgroup_id_remove(struct mem_cgroup *memcg) { if (memcg->id.id > 0) { - spin_lock(&memcg_idr_lock); - idr_remove(&mem_cgroup_idr, memcg->id.id); - spin_unlock(&memcg_idr_lock); - + xa_erase(&mem_cgroup_ids, memcg->id.id); memcg->id.id =3D 0; } } @@ -3420,7 +3403,7 @@ static inline void mem_cgroup_id_put(struct mem_cgrou= p *memcg) struct mem_cgroup *mem_cgroup_from_id(unsigned short id) { WARN_ON_ONCE(!rcu_read_lock_held()); - return idr_find(&mem_cgroup_idr, id); + return xa_load(&mem_cgroup_ids, id); } =20 #ifdef CONFIG_SHRINKER_DEBUG @@ -3519,11 +3502,10 @@ static struct mem_cgroup *mem_cgroup_alloc(struct m= em_cgroup *parent) if (!memcg) return ERR_PTR(error); =20 - memcg->id.id =3D mem_cgroup_alloc_id(); - if (memcg->id.id < 0) { - error =3D memcg->id.id; + error =3D xa_alloc(&mem_cgroup_ids, &memcg->id.id, NULL, + XA_LIMIT(1, MEM_CGROUP_ID_MAX), GFP_KERNEL); + if (error) goto fail; - } =20 memcg->vmstats =3D kzalloc(sizeof(struct memcg_vmstats), GFP_KERNEL_ACCOUNT); @@ -3664,9 +3646,7 @@ static int mem_cgroup_css_online(struct cgroup_subsys= _state *css) * publish it here at the end of onlining. This matches the * regular ID destruction during offlining. */ - spin_lock(&memcg_idr_lock); - idr_replace(&mem_cgroup_idr, memcg, memcg->id.id); - spin_unlock(&memcg_idr_lock); + xa_store(&mem_cgroup_ids, memcg->id.id, memcg, GFP_KERNEL); =20 return 0; offline_kmem: --=20 2.43.5