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? :-) Gilad -- Gilad Ben-Yossef Chief Coffee Drinker gilad@xxxxxxxxxxxxx Israel Cell: +972-52-8260388 US Cell: +1-973-8260388 http://benyossef.com "Unfortunately, cache misses are an equal opportunity pain provider." -- Mike Galbraith, LKML -- 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