On Wed, Jan 23, 2013 at 03:05:22PM -0800, Dan Magenheimer wrote: > I would be very interested in this topic. > > > Because of high density, low power and low price, flash storage (SSD) is a good > > candidate to partially replace DRAM. A quick answer for this is using SSD as > > swap. But Linux swap is designed for slow hard disk storage. There are a lot of > > challenges to efficiently use SSD for swap: > > > > 1. Lock contentions (swap_lock, anon_vma mutex, swap address space lock) > > 2. TLB flush overhead. To reclaim one page, we need at least 2 TLB flush. This > > overhead is very high even in a normal 2-socket machine. > > 3. Better swap IO pattern. Both direct and kswapd page reclaim can do swap, > > which makes swap IO pattern is interleave. Block layer isn't always efficient > > to do request merge. Such IO pattern also makes swap prefetch hard. > > Shaohua -- > > Have you considered the possibility of subverting the block layer entirely > and accessing the SSD like slow RAM rather than a fast I/O device? E.g. > something like NVME and as in this paper? > > http://static.usenix.org/events/fast12/tech/full_papers/Yang.pdf > > If you think this could be an option, it could make a very > interesting backend to frontswap (something like ramster). We had discussion about this before, but looks this requires very low latency storage, didn't take it serious yet. Thanks, Shaohua -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>