On Tuesday 02 March 2010, Mel Gorman wrote: > On Tue, Mar 02, 2010 at 10:17:51PM +0000, Alan Cox wrote: > > > -#define TTY_BUFFER_PAGE ((PAGE_SIZE - 256) / 2) > > > +#define TTY_BUFFER_PAGE (((PAGE_SIZE - sizeof(struct tty_buffer)) / > > > 2) & ~0xFF) > > > > Yes agreed I missed a '-1' > > Frans, would you mind testing your NAS box with the following patch > applied please? It should apply cleanly on top of 2.6.33-rc7. Thanks Thanks Mel. I've been running with this patch for about a week now and have so far not seen any more allocation failures. I've tried doing large rsyncs a few times. It's not 100% conclusive, but I would say it improves things and I've certainly not noticed any issues with the patch. Before I got the patch I noticed that the default value for vm.min_free_kbytes was only 1442 for this machine. Isn't that on the low side? Could that have been a factor? My concern is that, although fixing bugs in GFP_ATOMIC allocations is certainly very good, I can't help wondering why the system does not keep a bit more memory in reserve instead of using everything up for relatively silly things like cache and buffers. What if during an rsync I plug in some USB device whose driver has some valid GFP_ATOMIC allocations? Shouldn't the memory manager allow for such situations? Cheers, FJP > tty: Keep the default buffering to sub-page units > > We allocate during interrupts so while our buffering is normally diced > up small anyway on some hardware at speed we can pressure the VM > excessively for page pairs. We don't really need big buffers to be > linear so don't try so hard. > > In order to make this work well we will tidy up excess callers to > request_room, which cannot itself enforce this break up. > > [mel@xxxxxxxxx: Adjust TTY_BUFFER_PAGE to take padding into account] > Signed-off-by: Alan Cox <alan@xxxxxxxxxxxxxxx> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx> Tested-by: Frans Pop <fjp@xxxxxxxxx> -- 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>