On 09/05/2018 06:58 PM, Huang, Ying wrote: > Hi, Christopher, > > Christopher Lameter <cl@xxxxxxxxx> writes: > >> On Tue, 4 Sep 2018, Daniel Jordan wrote: >> >>> - Promoting huge page usage: With memory sizes becoming ever larger, huge >>> pages are becoming more and more important to reduce TLB misses and the >>> overhead of memory management itself--that is, to make the system scalable >>> with the memory size. But there are still some remaining gaps that prevent >>> huge pages from being deployed in some situations, such as huge page >>> allocation latency and memory fragmentation. >> >> You forgot the major issue that huge pages in the page cache are not >> supported and thus we have performance issues with fast NVME drives that >> are now able to do 3Gbytes per sec that are only possible to reach with >> directio and huge pages. > > Yes. That is an important gap for huge page. Although we have huge > page cache support for tmpfs, we lacks that for normal file systems. > >> IMHO the huge page issue is just the reflection of a certain hardware >> manufacturer inflicting pain for over a decade on its poor users by not >> supporting larger base page sizes than 4k. No such workarounds needed on >> platforms that support large sizes. Things just zoom along without >> contortions necessary to deal with huge pages etc. >> >> Can we come up with a 2M base page VM or something? We have possible >> memory sizes of a couple TB now. That should give us a million or so 2M >> pages to work with. > > That sounds a good idea. Don't know whether someone has tried this. IIRC, Hugh Dickins and some others at Google tried going down this path. There was a brief discussion at LSF/MM. It is something I too would like to explore in my spare time. -- Mike Kravetz
