On Tue, Nov 12, 2013 at 05:38:43PM +0200, Alexander Motin wrote: > 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 ?
Isn't compression done using dedicated ZFS-only ZIO threads? Why can't we just increase stack size for those threads? -- Pawel Jakub Dawidek http://www.wheelsystems.com FreeBSD committer http://www.FreeBSD.org Am I Evil? Yes, I Am! http://mobter.com
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