From nobody Thu Oct 2 15:33:22 2025 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (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 3D77C28727E for ; Mon, 15 Sep 2025 19:52:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757965949; cv=none; b=IG4wvhg0NkxFwdQgcH/fElotdImCIyukc0kNlmIdIV78Pf+597CJ8g/B+4OOias2P3E4KHJE1wna+S/vTUfnA/NKGg05M7H4EtBw2TfBPSPKIzoLt6Oa2UB8n8LjGUnSjDnvuoaKfir8wSTCmxMrIJxpiL7WZKQPOkmUCns/Uj0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757965949; c=relaxed/simple; bh=2cRPoohQ0MmOLZTf1mIp9HVeBlRdoTXyPcT7a1QwRos=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=NDWqic7mmWJD8AEAPReiE4hC8scafItqrhk6pvu0MA8pgS9jqkTkhN+5uo9CGj1QTYL/GOb/hFpwZC55nBet6RHmVQAuo/NWuugXL3BQYZruiR5MFlYAw3x1ycZyqOhmgZihSXjb+C96cBA/kl2TiGuEZ66avyOy086D29uvG5E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--fvdl.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=aoHn/lci; arc=none smtp.client-ip=209.85.210.201 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--fvdl.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="aoHn/lci" Received: by mail-pf1-f201.google.com with SMTP id d2e1a72fcca58-76e2eb787f2so4210206b3a.3 for ; Mon, 15 Sep 2025 12:52:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1757965947; x=1758570747; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=P8sdVCwgpzgSZpEZdIa2RxiH6JcLxFU2dfzzWpV7l6M=; b=aoHn/lciK1E0IpL6HkpUhkZXpQSn4JIJZgCuLGh8neIDD29SJpEScJf0Fqb5DYNsgP TFcVKH8WZsMLScRK8XyGvfSWPeuLRlJBQPE+heGSeii9xPF4RW4VqTxzoCGOFYWQuYbK gy0sXt2fNuXeHdXfDDTu3/gBiTALu+MGPrt43KABtPbhojYdhZRXLd727lv2mhi5xTno t2QzYTPJwWCmgxU3mDBnbZ4aNaF22KjojLjOcIZS5Lph28pA8MUIU4oIECnv3NA6jfu6 4J4cYX9dieIz8Df0kz1zGxTVpmt+1JeaRVQrtw4o/gerL9AnuHs8fVkJQGxU29E9jVpw y4vw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1757965947; x=1758570747; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=P8sdVCwgpzgSZpEZdIa2RxiH6JcLxFU2dfzzWpV7l6M=; b=LnSl0z1ZZfqSjQNceYoddu+5THb4W8TNw4jOQwOTjf4xEQznMDyZsEJYDZ4goiuiPF CSlmiOtmIkzJ7xEMKX6dAlZe9hLhH0SGbnLXSmhY0lDws3rCoOCdkbgCrIFvCN31Os0R F/I43ZKWkJ94hG6rW57EEoYADVz7KyLzC2V1aTrdYcZabLujYIPC5qa4SpM+k7UaR+Km M6GxukPgMPVl8+H0bWNSAKGDCOv/TjZ3L534USqxrISKF+hD/fWF4q6uFb1UjcIOkc56 sVyYvIq/JGAwS/j6aknW7JMVCk5hmYZsPZ31JMo2zUbs4oiIH4q57VslH0B1ETU4kFCM DO2g== X-Forwarded-Encrypted: i=1; AJvYcCU0J7ekzMM1Mdct/BXS10GMa493MgOuh8zEbZU+KpHQw80+56pDVSFeTOGcdNNBANIRURXJm0tFD7ka8bs=@vger.kernel.org X-Gm-Message-State: AOJu0YyCs4cVOWgW87TDvj+OexyZGOimPYbb+u2vYhLVBfmWmaYZpTa/ wHHpopzmqcJSZXBZhV0DoXKfFP52sH2zYMT8YHIJw9gLmhfC8dZHIXxtQQ58120utnW7Kxnj+A= = X-Google-Smtp-Source: AGHT+IHSrj8b6/0anPmsTtmAtpPpKBamD1vvncwaV7EMPgRBfcfV+2TtFZIJ4M8kZJb/oeTBgqjLyGgI X-Received: from pfaq4.prod.google.com ([2002:a05:6a00:a884:b0:772:32b1:58f9]) (user=fvdl job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:17a1:b0:772:8694:1d71 with SMTP id d2e1a72fcca58-77611f99ea8mr14148444b3a.0.1757965947238; Mon, 15 Sep 2025 12:52:27 -0700 (PDT) Date: Mon, 15 Sep 2025 19:51:47 +0000 In-Reply-To: <20250915195153.462039-1-fvdl@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250915195153.462039-1-fvdl@google.com> X-Mailer: git-send-email 2.51.0.384.g4c02a37b29-goog Message-ID: <20250915195153.462039-7-fvdl@google.com> Subject: [RFC PATCH 06/12] mm/cma: define and act on CMA_BALANCE flag From: Frank van der Linden To: akpm@linux-foundation.org, muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: hannes@cmpxchg.org, david@redhat.com, roman.gushchin@linux.dev, Frank van der Linden Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" When the CMA_BALANCE flag is set for a CMA area, it means that it opts in to CMA balancing. This means two things: 1) It allows movable allocations to be migrated in to it in the case of a CMA inbalance (too much free memory in CMA pageblocks as compared to other pageblocks). 2) It is allocated top-down, so that compaction will end up migrating pages in to it. Doing this will make sure that compaction doesn't aggrevate a CMA imbalance, and that it won't fight with CMA balance migration from non-CMA to CMA. Signed-off-by: Frank van der Linden --- include/linux/cma.h | 4 +++- mm/cma.c | 33 ++++++++++++++++++++++++++------- 2 files changed, 29 insertions(+), 8 deletions(-) diff --git a/include/linux/cma.h b/include/linux/cma.h index 0504580d61d0..6e98a516b336 100644 --- a/include/linux/cma.h +++ b/include/linux/cma.h @@ -26,6 +26,7 @@ enum cma_flags { __CMA_ZONES_INVALID, __CMA_ACTIVATED, __CMA_FIXED, + __CMA_BALANCE, }; =20 #define CMA_RESERVE_PAGES_ON_ERROR BIT(__CMA_RESERVE_PAGES_ON_ERROR) @@ -33,8 +34,9 @@ enum cma_flags { #define CMA_ZONES_INVALID BIT(__CMA_ZONES_INVALID) #define CMA_ACTIVATED BIT(__CMA_ACTIVATED) #define CMA_FIXED BIT(__CMA_FIXED) +#define CMA_BALANCE BIT(__CMA_BALANCE) =20 -#define CMA_INIT_FLAGS (CMA_FIXED|CMA_RESERVE_PAGES_ON_ERROR) +#define CMA_INIT_FLAGS (CMA_FIXED|CMA_RESERVE_PAGES_ON_ERROR|CMA_BALANCE) =20 struct cma; struct zone; diff --git a/mm/cma.c b/mm/cma.c index 53cb1833407b..6050d57f3c2e 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -272,6 +272,9 @@ static bool cma_next_free_range(struct cma_memrange *cm= r, static inline bool cma_should_balance_range(struct zone *zone, struct cma_memrange *cmr) { + if (!(cmr->cma->flags & CMA_BALANCE)) + return false; + if (page_zone(pfn_to_page(cmr->base_pfn)) !=3D zone) return false; =20 @@ -527,6 +530,12 @@ static bool __init basecmp(struct cma_init_memrange *m= lp, return mlp->base < mrp->base; } =20 +static bool __init revbasecmp(struct cma_init_memrange *mlp, + struct cma_init_memrange *mrp) +{ + return mlp->base > mrp->base; +} + /* * Helper function to create sorted lists. */ @@ -575,7 +584,8 @@ static int __init cma_fixed_reserve(phys_addr_t base, p= hys_addr_t size) } =20 static phys_addr_t __init cma_alloc_mem(phys_addr_t base, phys_addr_t size, - phys_addr_t align, phys_addr_t limit, int nid) + phys_addr_t align, phys_addr_t limit, int nid, + unsigned long flags) { phys_addr_t addr =3D 0; =20 @@ -588,7 +598,8 @@ static phys_addr_t __init cma_alloc_mem(phys_addr_t bas= e, phys_addr_t size, * like DMA/DMA32. */ #ifdef CONFIG_PHYS_ADDR_T_64BIT - if (!memblock_bottom_up() && limit >=3D SZ_4G + size) { + if (!(flags & CMA_BALANCE) && !memblock_bottom_up() + && limit >=3D SZ_4G + size) { memblock_set_bottom_up(true); addr =3D memblock_alloc_range_nid(size, align, SZ_4G, limit, nid, true); @@ -695,7 +706,7 @@ static int __init __cma_declare_contiguous_nid(phys_add= r_t *basep, if (ret) return ret; } else { - base =3D cma_alloc_mem(base, size, alignment, limit, nid); + base =3D cma_alloc_mem(base, size, alignment, limit, nid, flags); if (!base) return -ENOMEM; =20 @@ -851,7 +862,10 @@ int __init cma_declare_contiguous_multi(phys_addr_t to= tal_size, list_for_each_safe(mp, next, &ranges) { mlp =3D list_entry(mp, struct cma_init_memrange, list); list_del(mp); - list_insert_sorted(&final_ranges, mlp, basecmp); + if (flags & CMA_BALANCE) + list_insert_sorted(&final_ranges, mlp, revbasecmp); + else + list_insert_sorted(&final_ranges, mlp, basecmp); sizesum +=3D mlp->size; if (sizesum >=3D total_size) break; @@ -866,7 +880,12 @@ int __init cma_declare_contiguous_multi(phys_addr_t to= tal_size, list_for_each(mp, &final_ranges) { mlp =3D list_entry(mp, struct cma_init_memrange, list); size =3D min(sizeleft, mlp->size); - if (memblock_reserve(mlp->base, size)) { + if (flags & CMA_BALANCE) + start =3D (mlp->base + mlp->size - size); + else + start =3D mlp->base; + + if (memblock_reserve(start, size)) { /* * Unexpected error. Could go on to * the next one, but just abort to @@ -877,9 +896,9 @@ int __init cma_declare_contiguous_multi(phys_addr_t tot= al_size, } =20 pr_debug("created region %d: %016llx - %016llx\n", - nr, (u64)mlp->base, (u64)mlp->base + size); + nr, (u64)start, (u64)start + size); cmrp =3D &cma->ranges[nr++]; - cmrp->base_pfn =3D PHYS_PFN(mlp->base); + cmrp->base_pfn =3D PHYS_PFN(start); cmrp->early_pfn =3D cmrp->base_pfn; cmrp->count =3D size >> PAGE_SHIFT; cmrp->cma =3D cma; --=20 2.51.0.384.g4c02a37b29-goog