On Tue, 10 Aug 2010 12:12:06 +0900 (JST) KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> wrote: > > Subject: writeback: explicit low bound for vm.dirty_ratio > > From: Wu Fengguang <fengguang.wu@xxxxxxxxx> > > Date: Thu Jul 15 10:28:57 CST 2010 > > > > Force a user visible low bound of 5% for the vm.dirty_ratio interface. > > > > This is an interface change. When doing > > > > echo N > /proc/sys/vm/dirty_ratio > > > > where N < 5, the old behavior is pretend to accept the value, while > > the new behavior is to reject it explicitly with -EINVAL. This will > > possibly break user space if they checks the return value. > > Umm.. I dislike this change. Is there any good reason to refuse explicit > admin's will? Why 1-4% is so bad? Internal clipping can be changed later > but explicit error behavior is hard to change later. As a data-point, I had a situation a while back where I needed a value below 1 to get desired behaviour. The system had lots of RAM and fairly slow write-back (over NFS) so a 'sync' could take minutes. So I would much prefer allowing not only 1-4, but also fraction values!!! I can see no justification at all for setting a lower bound of 5. Even zero can be useful - for testing purposes mostly. NeilBrown > personally I prefer to > - accept all value, or > - clipping value in dirty_ratio_handler > > Both don't have explicit ABI change. > > Thanks. > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>