Deprecating the PCOMMIT Instruction
software.intel.com
Deprecating the PCOMMIT Instruction
1–10 of 26 posts
Re: Deprecating the PCOMMIT Instruction
#2This is a nice improvement. Now instead of having sfence/pcommit/sfence to flush writes to nvram, you would use just an sfence to ensure ordering with subsequent stores (e.g. a store that publishes the written data.)
Its analogous to fysnc() to ensure data reaches the disk in a way that survives power failure. This is like just treating all writes as fsynced and not needing to worry about fsync at all, like with O_DIRECT writes.
Re: Deprecating the PCOMMIT Instruction
#3Basically they've expanded the persistence domain from just the DIMMS, to the DIMMS and memory controller, obviating PCOMMIT.
Re: Deprecating the PCOMMIT Instruction
#4For a gentler introduction/motivation, consider http://danluu.com/clwb-pcommit/.
("Deprecating pcommit" means that persistent memory is simpler to use; persistent memory itself is not deprecated.)
Re: Deprecating the PCOMMIT Instruction
#5Okay HN, this is ELI5 time: is this instruction for interacting with SSDs that fit into DIMM slots?
Re: Deprecating the PCOMMIT Instruction
#6Okay HN, this is ELI5 time: is this instruction for interacting with SSDs that fit into DIMM slots?
It was the instruction for interacting with XPoint DIMMs (I wouldn't call them SSDs but whatever), but now you just use CLWB instead.
Re: Deprecating the PCOMMIT Instruction
#7Okay HN, this is ELI5 time: is this instruction for interacting with SSDs that fit into DIMM slots?
It was the instruction for interacting with XPoint DIMMs (I wouldn't call them SSDs but whatever), but now you just use CLWB instead.
Previously you would use CLWB, SFENCE, then PCOMMIT. Now you use CLWB, then SFENCE.
Re: Deprecating the PCOMMIT Instruction
#8They've either just averted or triggered a temporal paradox, I'm not sure which
Re: Deprecating the PCOMMIT Instruction
#9Does GCC use PCOMMIT?
Re: Deprecating the PCOMMIT Instruction
#10Does GCC use PCOMMIT?
No. "all known operating systems supporting persistent memory ... have already been updated to remove all uses of PCOMMIT."