Messages in this thread Patch in this message | | | From | Andrey Ryabinin <> | Subject | [PATCH v2 1/2] kernel: irq: use kmem_cache for allocating struct irq_desc | Date | Fri, 21 Nov 2014 19:08:18 +0300 |
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After enabling alignment checks in UBSan I've noticed a lot of reports like this:
UBSan: Undefined behaviour in ../kernel/irq/chip.c:195:14 member access within misaligned address ffff88003e80d6f8 for type 'struct irq_desc' which requires 64 byte alignment
struct irq_desc declared with ____cacheline_internodealigned_in_smp attribute. However in some cases it allocated dynamically via kmalloc(). In general case kmalloc() guaranties only sizeof(void *) alignment. We should use a separate slab cache to make struct irq_desc properly aligned on SMP configuration.
This also could slightly reduce memory usage on some configurations. E.g. in my setup sizeof(struct irq_desc) == 320. Which means that kmalloc-512 will be used for allocating irg_desc via kmalloc(). In that case using separate slab cache will save us 192 bytes per each irq_desc.
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com> Acked-by: David Rientjes <rientjes@google.com> ---
Changes since v1: - Drop kmem_cache_zalloc_node() and use kmem_cache_alloc_node with __GFP_ZERO flag.
kernel/irq/irqdesc.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c index a1782f8..c7a812c 100644 --- a/kernel/irq/irqdesc.c +++ b/kernel/irq/irqdesc.c @@ -23,6 +23,8 @@ */ static struct lock_class_key irq_desc_lock_class; +static struct kmem_cache *irq_desc_cachep; + #if defined(CONFIG_SMP) static void __init init_irq_default_affinity(void) { @@ -137,7 +139,7 @@ static struct irq_desc *alloc_desc(int irq, int node, struct module *owner) struct irq_desc *desc; gfp_t gfp = GFP_KERNEL; - desc = kzalloc_node(sizeof(*desc), gfp, node); + desc = kmem_cache_alloc_node(irq_desc_cachep, gfp | __GFP_ZERO, node); if (!desc) return NULL; /* allocate based on nr_cpu_ids */ @@ -158,7 +160,7 @@ static struct irq_desc *alloc_desc(int irq, int node, struct module *owner) err_kstat: free_percpu(desc->kstat_irqs); err_desc: - kfree(desc); + kmem_cache_free(irq_desc_cachep, desc); return NULL; } @@ -174,7 +176,7 @@ static void free_desc(unsigned int irq) free_masks(desc); free_percpu(desc->kstat_irqs); - kfree(desc); + kmem_cache_free(irq_desc_cachep, desc); } static int alloc_descs(unsigned int start, unsigned int cnt, int node, @@ -218,6 +220,8 @@ int __init early_irq_init(void) init_irq_default_affinity(); + irq_desc_cachep = KMEM_CACHE(irq_desc, SLAB_PANIC); + /* Let arch update nr_irqs and return the nr of preallocated irqs */ initcnt = arch_probe_nr_irqs(); printk(KERN_INFO "NR_IRQS:%d nr_irqs:%d %d\n", NR_IRQS, nr_irqs, initcnt); -- 2.1.3
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