On Sun 04-08-13 21:13:44, KOSAKI Motohiro wrote: > On Sun, Aug 4, 2013 at 4:07 AM, Michal Hocko <mhocko@xxxxxxx> wrote: > > On Sat 03-08-13 16:16:58, KOSAKI Motohiro wrote: > >> >>> You missed the "!". I'm proposing that setting the new bit 2 will > >> >>> permit people to prevent the new printk if it is causing them problems. > >> >> > >> >> No I don't. I'm sure almost all abuse users think our usage is correct. Then, > >> >> I can imagine all crazy applications start to use this flag eventually. > >> > > >> > I guess we do not care about those. If somebody wants to shoot his feet > >> > then we cannot do much about it. The primary motivation was to find out > >> > those that think this is right and they are willing to change the setup > >> > once they know this is not the right way to do things. > >> > > >> > I think that giving a way to suppress the warning is a good step. Log > >> > level might be to coarse and sysctl would be an overkill. > >> > >> When Dave Hansen reported this issue originally, he explained a lot of userland > >> developer misuse /proc/drop_caches because they don't understand what > >> drop_caches do. > >> So, if they never understand the fact, why can we trust them? I have no > >> idea. > > > > Well, most of that usage I have come across was legacy scripts which > > happened to work at a certain point in time because we sucked. > > Thinks have changed but such scripts happen to survive a long time. > > We are primarily interested in those. > > Well, if the main target is shell script, task_comm and pid don't help us > a lot. I suggest to add ppid too. I do not have any objections to add ppid. > >> Or, if you have different motivation w/ Dave, please let me know it. > > > > We have seen reports where users complained about performance drop down > > when in fact the real culprit turned out to be such a clever script > > which dropped caches on the background thinking it will help to free > > some memory. Such cases are tedious to reveal. > > Imagine such script have bit-2 and no logging output. Because > the script author think "we are doing the right thing". > Why distro guys want such suppress messages? I am not really pushing this suppressing functionality. I just understand that there might be some legitimate use for supressing and if that is a must for merging the printk, I can live with that. [...] -- Michal Hocko SUSE Labs -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>