syncing large mmaped files

[Tristan Verniquet]

I want to work with large (1-10G) files in memory but eventually sync them back out to disk. The problem is that the sync process appears to lock the file in kernel for the duration of the sync, which can run into minutes. This prevents other processes from reading from the file (unless they already have it mapped) for this whole time. Is there any way to prevent this? I think I read in a post somewhere about openbsd implementing partial-writes when it hits a file with lots of dirty pages in order to prevent this. Is there anything available for FreeBSD or is there another way around it?

Sorry if this is the wrong mailing list.