On 01/02/2012 01:59 PM, Gilad Ben-Yossef wrote: > On Sun, Jan 1, 2012 at 6:50 PM, Avi Kivity <avi@xxxxxxxxxx> wrote: > > On 01/01/2012 06:12 PM, Gilad Ben-Yossef wrote: > >> > > >> > Since this seems to be a common pattern, how about: > >> > > >> > zalloc_cpumask_var_or_all_online_cpus(&cpus, GFTP_ATOMIC); > >> > ... > >> > free_cpumask_var(cpus); > >> > > >> > The long-named function at the top of the block either returns a newly > >> > allocated zeroed cpumask, or a static cpumask with all online cpus set. > >> > The code in the middle is only allowed to set bits in the cpumask > >> > (should be the common usage). free_cpumask_var() needs to check whether > >> > the freed object is the static variable. > >> > >> Thanks for the feedback and advice! I totally agree the repeating > >> pattern needs abstracting. > >> > >> I ended up chosing to try a different abstraction though - basically a wrapper > >> on_each_cpu_cond that gets a predicate function to run per CPU to > >> build the mask > >> to send the IPI to. It seems cleaner to me not having to mess with > >> free_cpumask_var > >> and it abstracts more of the general pattern. > >> > > > > This converts the algorithm to O(NR_CPUS) from a potentially lower > > complexity algorithm. Also, the existing algorithm may not like to be > > driven by cpu number. Both are true for kvm. > > > > Right, I was only thinking on my own uses, which are O(NR_CPUS) by nature. > > I wonder if it would be better to create a safe_cpumask_var type with > its own alloc function > free and and sset_cpu function but no clear_cpu function so that the > compiler will catch > cases of trying to clear bits off of such a cpumask? > > It seems safer and also makes handling the free function easier. > > Does that makes sense or am I over engineering it? :-) It makes sense. Depends on the number of call sites, really. If there are several, consolidation helps, also makes it easier to further refactor. -- error compiling committee.c: too many arguments to function -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>