On Tue, Sep 30, 2014 at 10:53:47AM -0400, Valdis.Kletnieks@xxxxxx wrote: > On Tue, 30 Sep 2014 10:48:54 -0400, Matthew Wilcox said: > > > No, it doesn't try to do that. Wouldn't you be better served with an > > LD_PRELOAD that forces O_DIRECT on? > > Not when you don't want it on every file, and users are creating and > deleting files once in a while. A chattr-like command is easier and > more scalable than rebuilding the LD_PRELOAD every time the list of > files gets changed.... The more I think about this, the more I think this is a bad idea. When you have a file open with O_DIRECT, your I/O has to be done in 512-byte multiples, and it has to be aligned to 512-byte boundaries in memory. If an unsuspecting application has O_DIRECT forced on it, it isn't going to know to do that, and so all its I/Os will fail. It'll also be horribly inefficient if a program has the file mmaped. What problem are you really trying to solve? Some big files hogging the page cache? -- 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>