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Make use of kvmalloc if available and fix vmem_alloc implementation

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This patch implements use of kvmalloc for GFP_KERNEL allocations, which
may increase performance if the allocator is able to allocate physical
memory, if kvmalloc is available as a public kernel interface (since
v4.12). Otherwise it will simply fall back to virtual memory (vmalloc).

Also fix vmem_alloc implementation which can lead to slow allocations
since the first attempt with kmalloc does not make use of the noretry
flag but tells the linux kernel to retry several times before it fails.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Matt Ahrens <matt@delphix.com>
Signed-off-by: Sebastian Gottschall <s.gottschall@dd-wrt.com>
Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>
Closes #9034
This commit is contained in:
Michael Niewöhner
2019-07-21 19:34:07 +02:00
committed by Brian Behlendorf
parent c025008df5
commit 66955885e2
5 changed files with 124 additions and 11 deletions
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module/os/linux/spl/spl-kmem-cache.c
+18 -2
View File
@@ -203,7 +203,23 @@ kv_alloc(spl_kmem_cache_t *skc, int size, int flags)
ASSERT(ISP2(size));
ptr = (void *)__get_free_pages(lflags, get_order(size));
} else {
ptr = __vmalloc(size, lflags | __GFP_HIGHMEM, PAGE_KERNEL);
/*
* GFP_KERNEL allocations can safely use kvmalloc which may
* improve performance by avoiding a) high latency caused by
* vmalloc's on-access allocation, b) performance loss due to
* MMU memory address mapping and c) vmalloc locking overhead.
* This has the side-effect that the slab statistics will
* incorrectly report this as a vmem allocation, but that is
* purely cosmetic.
*
* For non-GFP_KERNEL allocations we stick to __vmalloc.
*/
if ((lflags & GFP_KERNEL) == GFP_KERNEL) {
ptr = spl_kvmalloc(size, lflags);
} else {
ptr = __vmalloc(size, lflags | __GFP_HIGHMEM,
PAGE_KERNEL);
}
}
/* Resulting allocated memory will be page aligned */
@@ -231,7 +247,7 @@ kv_free(spl_kmem_cache_t *skc, void *ptr, int size)
ASSERT(ISP2(size));
free_pages((unsigned long)ptr, get_order(size));
} else {
vfree(ptr);
spl_kmem_free_impl(ptr, size);
}
}