Disposal of a misleading M_TRYWAIT
Jeff Roberson
jroberson at chesapeake.net
Sun Mar 23 01:36:17 UTC 2008
On Sat, 22 Mar 2008, Matthew Dillon wrote:
>
> :> Since the advent of MBUMA in FreeBSD (whatever), M_TRYWAIT has meant
> :> M_WAITOK. (The reason for M_TRYWAIT itself was that an original mbuf's
> :> M_WAIT could return NULL.)
> :>
> :..
> :
> :This seems reasonable to me for exactly the reasons you stte. We might
> :simultaneously want to complete the M_DONTWAIT -> M_NOWAIT conversion. And
> :you can then remove the XXX comment in mbuf.h about phasing out M_TRYWAIT and
> :M_DONTWAIT. :-)
> :
> :Robert N M Watson
>
> The real issue is the fact that both the kernel malloc and the mbuf
> allocation APIs are using the same M_ prefix for their flags.
>
> We converted our mbuf allocator flags (aka M_DONTWAIT, M_TRYWAIT, M_WAIT)
> from M_ to MB_ and the code became a whole lot easier to read.
>
> I would not recommend converting the mbuf allocator to actually *USE*
> kernel malloc flags. The problem there is that you then have no clear
> delineation between M_ flags supported by malloc and M_ flags supported
> by the mbuf allocator.
They have been the same allocator for some time now. It makes more sense
for them to use the same flags.
Jeff
>
> -Matt
>
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