Hi.
While doing some performance tests I've found that LZ4 compression in
ZFS on FreeBSD each time allocates hash memory directly from VM, that on
multi-core system under significant load may consume more CPU time then
the compression itself. On 64-bit illumos that memory is allocated on
stack, but FreeBSD's kernel stack is smaller and has no sufficient space
(16K). I've made quite simple patch to reduce the allocation overhead by
creating allocation cache, same as it is done for ZIO. While for 64bit
illumos this patch is a nop, smaller architectures may still benefit
from it, same as FreeBSD does.
Any comments about it: http://people.freebsd.org/~mav/lz4_alloc.patch ?
--
Alexander Motin
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