> From: Loke, Chetan [mailto:Chetan.Loke@xxxxxxxxxxxx] > > From: Dan Magenheimer [mailto:dan.magenheimer@xxxxxxxxxx] > > Subject: RE: [RFC] non-preemptible kernel socket for RAMster > > > > > From: Loke, Chetan [mailto:Chetan.Loke@xxxxxxxxxxxx] > > > Sent: Tuesday, July 05, 2011 10:37 AM > > > To: Dan Magenheimer; netdev@xxxxxxxxxxxxxxx > > > Cc: Konrad Wilk; linux-mm > > > Subject: RE: [RFC] non-preemptible kernel socket for RAMster > > > > > > > In working on a kernel project called RAMster* (where RAM on a > > > > remote system may be used for clean page cache pages and for swap > > > > pages), I found I have need for a kernel socket to be used when > > > > > > How is RAMster+swap different than NBD's (pending etc?)support for > > > SWAP over NBD? > > > > I may be ignorant of details about NBD, but did some quick > > research using google. If I understand correctly, swap over > > NBD is still writing to a configured swap disk on the remote > > Hi - I thought NBD-server needs a backing store(a file). > Now the file itself could reside on a RAM-drive or disk-drive etc. > And so a remote NBD(disk or RAM) can be mounted locally as a swap > device. > The local client should still see it as a block device. > > I haven't used the RAM-drive feature myself but you may want to check if > it > works or even borrow that logic in your code. Actually, RAMster is using a much more flexible type of RAM-drive; it is built on top of Transcendent Memory and on top of zcache (and thus on top of cleancache and frontswap). A RAM-drive is fixed size so is not very suitable for the flexibility required for RAMster. For example, suppose you have two machines A and B. At one point in time A is overcommitted and needs to swap and B is relatively idle. Then later, B is overcommitted and needs to swap and A is relatively idle. RAMster can handle this entirely dynamically, a RAM-drive cannot. > > machine. RAMster is swapping to *RAM* on the remote machine. > > The idea is that most machines are very overprovisioned in > > RAM, and are rarely using all of their RAM, especially when > > a machine is (mostly) idle. In other words, the "max of > > the sums" of RAM usage on a group of machines is much lower > > than the "sum of the max" of RAM usage. > > > > So if the network is sufficiently faster than disk for > > moving a page of data, RAMster provides a significant > > performance improvement. OR RAMster may allow a significant > > reduction in the total amount of RAM across a data center. > > > > The version of RAMster I am working on now is really > > a proof-of-concept that works over sockets, using the > > ocfs2 cluster layer. One can easily envision a future > > "exo-fabric" which allows one machine to write to the > > RAM of another machine... for this future hardware, > > RAMster becomes much more interesting. > > Or you can also try scst-in-RAM mode(if you want to experiment with > different fabrics). Thanks. Could you provide a pointer for this? I found the SCST sourceforge page but no obvious references to scst-in-ram-mode. (But also, since it appears to be SCSI-related, I wonder if it also assumes a fixed size target device, RAM or disk or ??) Dan -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href