On Thu, Jul 16, 2015 at 12:04:59PM -0700, Andres Lagar-Cavilla wrote: > On Thu, Jul 16, 2015 at 2:28 AM, Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> > wrote: > > > On Wed, Jul 15, 2015 at 12:03:18PM -0700, Andres Lagar-Cavilla wrote: > > > For both /proc/kpage* interfaces you add (and more critically for the > > > rmap-causing one, kpageidle): > > > > > > It's a good idea to do cond_sched(). Whether after each pfn, each Nth > > > pfn, each put_user, I leave to you, but a reasonable cadence is > > > needed, because user-space can call this on the entire physical > > > address space, and that's a lot of work to do without re-scheduling. > > > > I really don't think it's necessary. These files can only be > > read/written by the root, who has plenty ways to kill the system anyway. > > The program that is allowed to read/write these files must be conscious > > and do it in batches of reasonable size. AFAICS the same reasoning > > already lays behind /proc/kpagecount and /proc/kpageflag, which also do > > not thrust the "right" batch size on their readers. > > > > Beg to disagree. You're conflating intended use with system health. A > cond_sched() is a one-liner. I would still prefer not to clutter the code with cond_resched's, but I don't think it's a matter worth arguing upon, so I'll prepare a patch that makes all /proc/kapge* files issue cond_resched periodically and leave it up to Andrew to decide if it should be applied or not. Thanks, Vladimir -- 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>