On Thu, Jul 25, 2019 at 10:15:29AM -0700, Mike Kravetz wrote: > On 7/25/19 1:13 AM, Mel Gorman wrote: > > On Wed, Jul 24, 2019 at 10:50:14AM -0700, Mike Kravetz wrote: > >> When allocating hugetlbfs pool pages via /proc/sys/vm/nr_hugepages, > >> the pages will be interleaved between all nodes of the system. If > >> nodes are not equal, it is quite possible for one node to fill up > >> before the others. When this happens, the code still attempts to > >> allocate pages from the full node. This results in calls to direct > >> reclaim and compaction which slow things down considerably. > >> > >> When allocating pool pages, note the state of the previous allocation > >> for each node. If previous allocation failed, do not use the > >> aggressive retry algorithm on successive attempts. The allocation > >> will still succeed if there is memory available, but it will not try > >> as hard to free up memory. > >> > >> Signed-off-by: Mike Kravetz <mike.krav...@oracle.com> > > > > set_max_huge_pages can fail the NODEMASK_ALLOC() alloc which you handle > > *but* in the event of an allocation failure this bug can silently recur. > > An informational message might be justified in that case in case the > > stall should recur with no hint as to why. > > Right. > Perhaps a NODEMASK_ALLOC() failure should just result in a quick exit/error. > If we can't allocate a node mask, it is unlikely we will be able to allocate > a/any huge pages. And, the system must be extremely low on memory and there > are likely other bigger issues. >
That might be better overall, you make a valid point that a failed kmalloc is not a good sign for hugetlbfs allocations. > There have been discussions elsewhere about discontinuing the use of > NODEMASK_ALLOC() and just putting the mask on the stack. That may be > acceptable here as well. > They can be big and while this particular path would be relatively safe, I think the fact that there will not be much functional difference between allocating on the stack and a failed kmalloc in terms of hugetlbfs allocation success rates. > > Technically passing NULL into > > NODEMASK_FREE is also safe as kfree (if used for that kernel config) can > > handle freeing of a NULL pointer. However, that is cosmetic more than > > anything. Whether you decide to change either or not; > > Yes. > I will clean up with an updated series after more feedback. > Thanks. -- Mel Gorman SUSE Labs
