On 2015/8/1 7:24, Dave Hansen wrote: > On 07/31/2015 02:30 AM, Xishi Qiu wrote: >> __free_one_page() will judge whether the the next-highest order is free, >> then add the block to the tail or not. So when we split large order block, >> add the small block to the tail, it will reduce fragment. > > It's an interesting idea, but what does it do in practice? Can you > measure a decrease in fragmentation? > > Further, the comment above the function says: > * The order of subdivision here is critical for the IO subsystem. > * Please do not alter this order without good reasons and regression > * testing. > > Has there been regression testing? > > Also, this might not do very much good in practice. If you are > splitting a high-order page, you are doing the split because the > lower-order lists are empty. So won't that list_add() be to an empty
Hi Dave, I made a mistake, you are right, all the lower-order lists are empty, so it is no sense to add to the tail. Thanks, Xishi Qiu > list most of the time? Or does the __rmqueue_fallback() > largest->smallest logic dominate? > > . > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
