Messages in this thread | | | Date | Tue, 21 Jan 2014 19:43:10 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 5/5] lockdep: pack subclass/trylock/read/check into a single argument |
| |
On 01/21, Dave Jones wrote: > > On Tue, Jan 21, 2014 at 03:10:22PM +0100, Peter Zijlstra wrote: > > > > I tried the below but filed to see my vmlinux shrink, maybe I'm just not > > building the right kernel, or otherwise GCC is stupid. > > > > -extern void lock_acquire(struct lockdep_map *lock, unsigned int subclass, > > - int trylock, int read, int check, > > - struct lockdep_map *nest_lock, unsigned long ip); > > +struct lockdep_acquire_flags { > > + unsigned long subclass : 3; > > + unsigned long trylock : 1; > > + unsigned long read : 2; > > + unsigned long check : 1; > > +}; > > As it's only 7 bits here, could we pack them into a char ?
Do you mean __attribute__((packed)) ?
Suprizingly it helps a bit. Still "size vmlinux" is worse than with bitmasks.
But I agreed that the code looks simpler with bitfields, so perhaps this patch is better.
Oleg.
| |