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. >> - Reducing the number of users of mmap_sem: This semaphore is frequently >> used throughout the kernel. In order to facilitate scaling this longstanding >> bottleneck, these uses should be documented and unnecessary users should be >> fixed. > > > Large page sizes also reduce contention there. Yes. >> If you haven't already done so, please let us know if you are interested in >> attending, or have suggestions for other attendees. > > Certainly interested in attending but this overlaps supercomputing 2018 in > Dallas Texas... Sorry to know this. It appears that there are too many conferences in November... Best Regards, Huang, Ying
