Messages in this thread | | | Date | Fri, 10 Feb 2006 15:52:15 +1100 | From | Nick Piggin <> | Subject | Re: msync() behaviour broken for MS_ASYNC, revert patch? |
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Andrew Morton wrote: > Nick Piggin <nickpiggin@yahoo.com.au> wrote: > >>>Secondly, consider the behaviour of the above application if it is modifying >> >> > the same page relatively frequently (quite likely). If MS_ASYNC starts I/O >> > immediately, that page will get written 10, 100 or 1000 times per second. >> > If MS_ASYNC leaves it to pdflush, that page gets written once per 30 >> > seconds, so we do far much less I/O. >> > >> > We just don't know. It's better to leave it up to the application designer >> > rather than lumping too many operations into the one syscall. >> >> Well it remains the same conceptual operation (asynchronously "schedule" >> dirty pages for writeout). However it simply becomes more useful to start >> the writeout immediately, given that's the (pretty explicit) hint that is >> given to us. > > > If you want to start the I/O now, fine, start the I/O now. > > If you don't want to start I/O now, fine, don't start I/O now. > > If msync() were to unconditionally start I/O, you don't get that option. >
Huh? Sure you do.
If you want to start the IO *now* without waiting on it, call msync(MS_ASYNC) If you don't want to start the IO now, that's really easy, do nothing. If you want to start the IO now and also wait for it to finish, call msync(MS_SYNC)
Presently, the first option is unavailable.
> It's pretty simple, isn't it? >
Yes.
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