> > Hello, Rulinhuang! > > > Hi Uladzislau and Andrew, we have rebased it(Patch v4) on branch > > mm-unstable and remeasured it. Could you kindly help confirm if this > > is the right base to work on? > > Compared to the previous result at kernel v6.7 with a 5% performance > > gain on intel icelake(160 vcpu), we only had a 0.6% with this commit > > base. But we think our modification still has some significance. On > > the one hand, this does reduce a critical section. On the other hand, > > we have a 4% performance gain on intel sapphire rapids(224 vcpu), > > which suggests more performance improvement would likely be achieved > > when the core count of processors increases to hundreds or even > > thousands. > > Thank you again for your comments. > > > According to the patch that was a correct rebase. Right a small delta on your > 160 CPUs is because of removing a contention. As for bigger systems it is > bigger impact, like you point here on your 224 vcpu results where you see %4 > perf improvement. > > So we should fix it. But the way how it is fixed is not optimal from my point of > view, because the patch that is in question spreads the internals from > alloc_vmap_area(), like inserting busy area, across many parts now. > > -- > Uladzislau Rezki Our modifications in patch 5 not only achieve the original effect, but also cancel the split of alloc_vmap_area()and setup_vmalloc_vm() is placed without lock and lengthen the critical section. Without splitting alloc_vmap_area(), putting setup_vmalloc_vm() directly into it is all we can think of. Regarding Baoquan’s changes, we think that: We prefer put setup_vmalloc_vm() function not placed inside the critical section and it is no need to lengthen the critical section. We prefer use judging (vm_data) rather than ((!(va_flags & VMAP_RAM) && vm), and it is enough to deetermine the conditions for assignment. The change seem to be wandering about the judgment of va_flags. Hi Uladzislau, could you please let us know if you have any better suggestions on the modification scheme? Thank you for your advice!
