On Tue, Aug 21, 2007 at 05:34:38PM +0200, Roch - PAE wrote: > > adrian cockcroft writes: > > Why can't you adapt ZFS for swap? It does the transactional clustering of > > random writes into sequential related blocks, aggressive prefetch on read, > > and would also guard against corrupt blocks in swap. Anon-ZFS? > > Adrian > > Good point. And It works already, swap to a zvol > > http://blogs.sun.com/scottdickson/entry/fun_with_zvols_-_swap > ZFS admin guide (currently down): > http://docs.sun.com/app/docs/doc/819-5461/6n7ht6qsl?a=view > > For output ZFS will get streaming perf out of the disks and > as you say will order pages from a given object (an anon segment?) > > For swapin, I don't think we'll trigger read ahead (zfetch > code) but the low level vdev prefetch could be activated. The > heuristic was recently adjusted so that it won't trigger on > data blocks. We might need to revisit this for zvol/swap case. > > -r > > PS. I would set up the zvol to use volblocksize == pagesize.
The swap to zpool idea is very interesting. But this brings up another question in the puzzle for us... What is this mythical creature, a page size, in the Solaris VM, when it comes to tuning? You have variable pages in solaris, but in practice you can only get a single large page on x86 (sparc seems to be better) which indicates a horrendous amount of fragmentation in the VM, never myind how that is reflected in swap, enough that you just can't get large page performance. In any case, are you optimizing for 2k or 2M pages? Does it make a difference? I suspect it skews some of the considerations, but I'm not sure exactly how. -Peter -- The 5 year plan: In five years we'll make up another plan. Or just re-use this one. _______________________________________________ perf-discuss mailing list perf-discuss@opensolaris.org
