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From: Baoquan He <bhe@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, akpm@linux-foundation.org, corbet@lwn.net,
	hch@lst.de, cl@linux.com, bhe@redhat.com
Subject: [PATCH 2/2] dma-pool: allow user to disable atomic pool
Date: Fri, 17 Dec 2021 17:08:27 +0800	[thread overview]
Message-ID: <20211217090827.101938-3-bhe@redhat.com> (raw)
In-Reply-To: <20211217090827.101938-1-bhe@redhat.com>

In the current code, three atomic memory pools are always created,
atomic_pool_kernel|dma|dma32, even though 'coherent_pool=0' is
specified in kernel command line. In fact, atomic pool is only
necessary when CONFIG_DMA_DIRECT_REMAP=y or mem_encrypt_active=y
which are needed on few ARCHes.

So change code to allow user to disable atomic pool by specifying
'coherent_pool=0'.

Meanwhile, update the relevant document in kernel-parameter.txt.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 3 ++-
 kernel/dma/pool.c                               | 7 +++++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index ec4d25e854a8..d7015309614b 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -664,7 +664,8 @@
 
 	coherent_pool=nn[KMG]	[ARM,KNL]
 			Sets the size of memory pool for coherent, atomic dma
-			allocations. Otherwise the default size will be scaled
+			allocations. A value of 0 disables the three atomic
+			memory pool. Otherwise the default size will be scaled
 			with memory capacity, while clamped between 128K and
 			1 << (PAGE_SHIFT + MAX_ORDER-1).
 
diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index 5f84e6cdb78e..5a85804b5beb 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -21,7 +21,7 @@ static struct gen_pool *atomic_pool_kernel __ro_after_init;
 static unsigned long pool_size_kernel;
 
 /* Size can be defined by the coherent_pool command line */
-static size_t atomic_pool_size;
+static unsigned long atomic_pool_size = -1;
 
 /* Dynamic background expansion when the atomic pool is near capacity */
 static struct work_struct atomic_pool_work;
@@ -188,11 +188,14 @@ static int __init dma_atomic_pool_init(void)
 {
 	int ret = 0;
 
+	if (!atomic_pool_size)
+		return 0;
+
 	/*
 	 * If coherent_pool was not used on the command line, default the pool
 	 * sizes to 128KB per 1GB of memory, min 128KB, max MAX_ORDER-1.
 	 */
-	if (!atomic_pool_size) {
+	if (atomic_pool_size == -1) {
 		unsigned long pages = totalram_pages() / (SZ_1G / SZ_128K);
 		pages = min_t(unsigned long, pages, MAX_ORDER_NR_PAGES);
 		atomic_pool_size = max_t(size_t, pages << PAGE_SHIFT, SZ_128K);
-- 
2.26.0


  parent reply	other threads:[~2021-12-17  9:08 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-17  9:08 [PATCH 0/2] Clean up document and small improvement of " Baoquan He
2021-12-17  9:08 ` [PATCH 1/2] docs: kernel-parameters: Update to reflect the current default size " Baoquan He
2021-12-21  8:50   ` Christoph Hellwig
2021-12-17  9:08 ` Baoquan He [this message]
2021-12-21  8:52   ` [PATCH 2/2] dma-pool: allow user to disable " Christoph Hellwig
  -- strict thread matches above, loose matches on Subject: below --
2021-06-24  5:20 [PATCH RFC 0/2] " Baoquan He
2021-06-24  5:20 ` [PATCH 2/2] " Baoquan He

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