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dma/pool: Avoid allocating redundant pools

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On smaller systems, e.g. embedded arm64, it is common for all memory
to end up in ZONE_DMA32 or even ZONE_DMA. In such cases it is redundant
to allocate a nominal pool for an empty higher zone that just ends up
coming from a lower zone that should already have its own pool anyway.
We already have logic to skip allocating a ZONE_DMA pool when that is
empty, so generalise that to save memory in the case of other zones too.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Vladimir Kondratiev <vladimir.kondratiev@mobileye.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/8ab8d8a620dee0109f33f5cb63d6bfeed35aac37.1768230104.git.robin.murphy@arm.com
This commit is contained in:
Robin Murphy
2026-01-12 15:46:38 +00:00
committed by Marek Szyprowski
parent 6626734dd2
commit c6ccd09880
1 changed files with 14 additions and 5 deletions
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19
kernel/dma/pool.c
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@@ -184,6 +184,12 @@ static __init struct gen_pool *__dma_atomic_pool_init(size_t pool_size,
return pool;
}
#ifdef CONFIG_ZONE_DMA32
#define has_managed_dma32 has_managed_zone(ZONE_DMA32)
#else
#define has_managed_dma32 false
#endif
static int __init dma_atomic_pool_init(void)
{
int ret = 0;
@@ -199,17 +205,20 @@ static int __init dma_atomic_pool_init(void)
}
INIT_WORK(&atomic_pool_work, atomic_pool_work_fn);
atomic_pool_kernel = __dma_atomic_pool_init(atomic_pool_size,
/* All memory might be in the DMA zone(s) to begin with */
if (has_managed_zone(ZONE_NORMAL)) {
atomic_pool_kernel = __dma_atomic_pool_init(atomic_pool_size,
GFP_KERNEL);
if (!atomic_pool_kernel)
ret = -ENOMEM;
if (!atomic_pool_kernel)
ret = -ENOMEM;
}
if (has_managed_dma()) {
atomic_pool_dma = __dma_atomic_pool_init(atomic_pool_size,
GFP_KERNEL | GFP_DMA);
if (!atomic_pool_dma)
ret = -ENOMEM;
}
if (IS_ENABLED(CONFIG_ZONE_DMA32)) {
if (has_managed_dma32) {
atomic_pool_dma32 = __dma_atomic_pool_init(atomic_pool_size,
GFP_KERNEL | GFP_DMA32);
if (!atomic_pool_dma32)
@@ -228,7 +237,7 @@ static inline struct gen_pool *dma_guess_pool(struct gen_pool *prev, gfp_t gfp)
return atomic_pool_dma ?: atomic_pool_dma32 ?: atomic_pool_kernel;
if (gfp & GFP_DMA32)
return atomic_pool_dma32 ?: atomic_pool_dma ?: atomic_pool_kernel;
return atomic_pool_kernel;
return atomic_pool_kernel ?: atomic_pool_dma32 ?: atomic_pool_dma;
}
if (prev == atomic_pool_kernel)
return atomic_pool_dma32 ? atomic_pool_dma32 : atomic_pool_dma;