On Wed, 8 Dec 1999, Matthew Dillon wrote:
> I would like to add a new MAP_ flag to mmap() prior to the 4.x freeze.
> The purpose of the flag is to prevent the syncer from syncing the
> file underlying the map. The VM system will still page to the file as
> needed and, of course, the data will remain consistent with the file.
>
> This will allow normal files to be used to back (for example) shared
> memory without incuring the extra overhead that sync causes every 30
> seconds. Currently it is not possible to use normal files in this
> fashion (verses using MAP_ANON, for which sharability is limited, or
> SysV shared memory which often has unexpected limitations) and still
> have an efficient system.
>
> The flag will be called MAP_NOSYNC
>
> Operationally, the syncer will not sync the file while any mmap()'s
> exist with that flag set. Once such flagged maps go away, the syncer
> will be able to sync the file (if it still exists).
>
> Comments are welcome.
I'd like to see this happen, go for it! :)
Don't forget how getnewbuf refils the buffers though, it will need to
somehow to communicate to the syncer to disregard MAP_NOSYNC during a
shortage... ? :)
-Alfred
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