Commit 71cdec4f authored Jun 21, 2020 by David Rientjes Committed by Christoph Hellwig Jun 29, 2020

dma-mapping: warn when coherent pool is depleted



When a DMA coherent pool is depleted, allocation failures may or may not
get reported in the kernel log depending on the allocator.

The admin does have a workaround, however, by using coherent_pool= on the
kernel command line.

Provide some guidance on the failure and a recommended minimum size for
the pools (double the size).

Signed-off-by: David Rientjes <rientjes@google.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Christoph Hellwig <hch@lst.de>

parent 9ebcfadb

kernel/dma/pool.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -239,12 +239,16 @@ void dma_alloc_from_pool(struct device dev, size_t size,
		}

		val = gen_pool_alloc(pool, size);
		if (val) {
		if (likely(val)) {
		phys_addr_t phys = gen_pool_virt_to_phys(pool, val);

		*ret_page = pfn_to_page(__phys_to_pfn(phys));
		ptr = (void *)val;
		memset(ptr, 0, size);
		} else {
		WARN_ONCE(1, "DMA coherent pool depleted, increase size "
		"(recommended min coherent_pool=%zuK)\n",
		gen_pool_size(pool) >> 9);
		}
		if (gen_pool_avail(pool) < atomic_pool_size)
		schedule_work(&atomic_pool_work);

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