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Optimize vmem_alloc() retry path

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For performance reasons the reworked kmem code maps vmem_alloc() to
kmalloc_node() for allocations less than spa_kmem_alloc_max.  This
allows for more concurrency in the system and less contention of
the virtual address space.  Generally, this is a good thing.

However, in the case when the kmalloc_node() fails it makes little
sense to retry it using kmalloc_node() again.  It will likely fail
in exactly the same way.  A smarter strategy is to abandon this
optimization and retry using spl_vmalloc() which is very likely
to succeed.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Closes #428
This commit is contained in:
Brian Behlendorf 2015-01-29 16:08:25 -08:00
parent 54cccfc2e3
commit c7db36a3c4
1 changed files with 11 additions and 1 deletions
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12
module/spl/spl-kmem.c
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@ -149,6 +149,7 @@ inline void *
spl_kmem_alloc_impl(size_t size, int flags, int node) spl_kmem_alloc_impl(size_t size, int flags, int node)
{ {
gfp_t lflags = kmem_flags_convert(flags); gfp_t lflags = kmem_flags_convert(flags);
int use_vmem = 0;
void *ptr; void *ptr;
/* /*
@ -182,7 +183,7 @@ spl_kmem_alloc_impl(size_t size, int flags, int node)
* impact performance so frequently manipulating the virtual * impact performance so frequently manipulating the virtual
* address space is strongly discouraged. * address space is strongly discouraged.
*/ */
if (unlikely(size > spl_kmem_alloc_max)) { if ((size > spl_kmem_alloc_max) || use_vmem) {
if (flags & KM_VMEM) { if (flags & KM_VMEM) {
ptr = spl_vmalloc(size, lflags, PAGE_KERNEL); ptr = spl_vmalloc(size, lflags, PAGE_KERNEL);
} else { } else {
@ -195,6 +196,15 @@ spl_kmem_alloc_impl(size_t size, int flags, int node)
if (likely(ptr) || (flags & KM_NOSLEEP)) if (likely(ptr) || (flags & KM_NOSLEEP))
return (ptr); return (ptr);
/*
* For vmem_alloc() and vmem_zalloc() callers retry immediately
* using spl_vmalloc() which is unlikely to fail.
*/
if ((flags & KM_VMEM) && (use_vmem == 0)) {
use_vmem = 1;
continue;
}
if (unlikely(__ratelimit(&kmem_alloc_ratelimit_state))) { if (unlikely(__ratelimit(&kmem_alloc_ratelimit_state))) {
printk(KERN_WARNING printk(KERN_WARNING
"Possible memory allocation deadlock: " "Possible memory allocation deadlock: "