2017-09-26 17:51 GMT+08:00 Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>: > On Tue, Sep 26, 2017 at 04:46:42PM +0800, Hui Zhu wrote: >> Current HighAtomic just to handle the high atomic page alloc. >> But I found that use it handle the normal unmovable continuous page >> alloc will help to against long-term fragmentation. >> > > This is not wise. High-order atomic allocations do not always have a > smooth recovery path such as network drivers with large MTUs that have no > choice but to drop the traffic and hope for a retransmit. That's why they > have the highatomic reserve. If the reserve is used for normal unmovable > allocations then allocation requests that could have waited for reclaim > may cause high-order atomic allocations to fail. Changing it may allow > improve latencies in some limited cases while causing functional failures > in others. If there is a special case where there are a large number of > other high-order allocations then I would suggest increasing min_free_kbytes > instead as a workaround. I think let 0 order unmovable page alloc and other order unmovable pages alloc use different migrate types will help against long-term fragmentation. Do you think kernel can add a special migrate type for big than 0 order unmovable pages alloc? Thanks, Hui > > -- > 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
