On Tue, Oct 25, 2011 at 10:39:34PM +0300, Pekka Enberg wrote: > Hi Mel, > > On Tue, Oct 25, 2011 at 2:23 PM, Mel Gorman <mgorman@xxxxxxx> wrote: > > I see what you mean with GFP_NOIO but there is an important difference > > between GFP_NOIO and suspend. A GFP_NOIO low-order allocation currently > > implies __GFP_NOFAIL as commented on in should_alloc_retry(). If no progress > > is made, we call wait_iff_congested() and sleep for a bit. As the system > > is running, kswapd and other process activity will proceed and eventually > > reclaim enough pages for the GFP_NOIO allocation to succeed. In a running > > system, GFP_NOIO can stall for a period of time but your patch will cause > > the allocation to fail. While I expect callers return ENOMEM or handle > > the situation properly with a wait-and-retry loop, there will be > > operations that fail that used to succeed. This is why I'd prefer it was > > a suspend-specific fix unless we know there is a case where a machine > > livelocks due to a GFP_NOIO allocation looping forever and even then I'd > > wonder why kswapd was not helping. > > I'm not that happy about your patch because it's going to the > direction where the page allocator is special-casing for suspension. Suspend really is a special case. While I'd prefer to avoid special casing it like this, I prefer it a *lot* more than failing GFP_NOIO allocations that used to succeed. -- Mel Gorman 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>