On Fri, 2016-09-09 at 14:43 +0900, Minchan Kim wrote: > Hi Huang, > > On Wed, Sep 07, 2016 at 09:45:59AM -0700, Huang, Ying wrote: > > > > From: Huang Ying <ying.huang@xxxxxxxxx> > > > > This patchset is to optimize the performance of Transparent Huge Page > > (THP) swap. > > > > Hi, Andrew, could you help me to check whether the overall design is > > reasonable? > > > > Hi, Hugh, Shaohua, Minchan and Rik, could you help me to review the > > swap part of the patchset? Especially [01/10], [04/10], [05/10], > > [06/10], [07/10], [10/10]. > > > > Hi, Andrea and Kirill, could you help me to review the THP part of the > > patchset? Especially [02/10], [03/10], [09/10] and [10/10]. > > > > Hi, Johannes, Michal and Vladimir, I am not very confident about the > > memory cgroup part, especially [02/10] and [03/10]. Could you help me > > to review it? > > > > And for all, Any comment is welcome! > > > > > > Recently, the performance of the storage devices improved so fast that > > we cannot saturate the disk bandwidth when do page swap out even on a > > high-end server machine. Because the performance of the storage > > device improved faster than that of CPU. And it seems that the trend > > will not change in the near future. On the other hand, the THP > > becomes more and more popular because of increased memory size. So it > > becomes necessary to optimize THP swap performance. > > > > The advantages of the THP swap support include: > > > > - Batch the swap operations for the THP to reduce lock > > acquiring/releasing, including allocating/freeing the swap space, > > adding/deleting to/from the swap cache, and writing/reading the swap > > space, etc. This will help improve the performance of the THP swap. > > > > - The THP swap space read/write will be 2M sequential IO. It is > > particularly helpful for the swap read, which usually are 4k random > > IO. This will improve the performance of the THP swap too. > > > > - It will help the memory fragmentation, especially when the THP is > > heavily used by the applications. The 2M continuous pages will be > > free up after THP swapping out. > I just read patchset right now and still doubt why the all changes > should be coupled with THP tightly. Many parts(e.g., you introduced > or modifying existing functions for making them THP specific) could > just take page_list and the number of pages then would handle them > without THP awareness. > > For example, if the nr_pages is larger than SWAPFILE_CLUSTER, we > can try to allocate new cluster. With that, we could allocate new > clusters to meet nr_pages requested or bail out if we fail to allocate > and fallback to 0-order page swapout. With that, swap layer could > support multiple order-0 pages by batch. > > IMO, I really want to land Tim Chen's batching swapout work first. > With Tim Chen's work, I expect we can make better refactoring > for batching swap before adding more confuse to the swap layer. > (I expect it would share several pieces of code for or would be base > for batching allocation of swapcache, swapslot) Minchan, Ying and I do plan to send out a new patch series on batching swapout and swapin plus a few other optimization on the swapping of regular sized pages. Hopefully we'll be able to do that soon after we fixed up a few things and retest. Tim -- 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>