Hello Robert, I think our concerns are roughly classified into two:
(1) Performance (2) Consistency And your "different concern" is rather into (2), I think. I'm also worried about it, but I have no good answer for now. I suppose mmap(flags|=MAP_SHARED) called by multiple backend processes for the same file works consistently for both PMEM and non-PMEM devices. However, I have not found any evidence such as specification documents yet. I also made a tiny program calling memcpy() and msync() on the same mmap()-ed file but mutually distinct address range in parallel, and found that there was no corrupted data. However, that result does not ensure any consistency I'm worried about. I could give it up if there *were* corrupted data... So I will go to (1) first. I will test the way Heikki told us to answer whether the cost of mmap() and munmap() per WAL segment, etc, is reasonable or not. If it really is, then I will go to (2). Best regards, Takashi -- Takashi Menjo <takashi.menjou...@hco.ntt.co.jp> NTT Software Innovation Center
