On Fri, Apr 16, 2021 at 11:57:03PM +0530, Pratik Sampat wrote: > > > On 16/04/21 10:43 pm, Roman Gushchin wrote: > > On Fri, Apr 16, 2021 at 08:58:33PM +0530, Pratik Sampat wrote: > > > Hello Dennis, > > > > > > I apologize for the clutter of logs before, I'm pasting the logs of > > > before and > > > after the percpu test in the case of the patchset being applied on > > > 5.12-rc6 and > > > the vanilla kernel 5.12-rc6. > > > > > > On 16/04/21 7:48 pm, Dennis Zhou wrote: > > > > Hello, > > > > > > > > On Fri, Apr 16, 2021 at 06:26:15PM +0530, Pratik Sampat wrote: > > > > > Hello Roman, > > > > > > > > > > I've tried the v3 patch series on a POWER9 and an x86 KVM setup. > > > > > > > > > > My results of the percpu_test are as follows: > > > > > Intel KVM 4CPU:4G > > > > > Vanilla 5.12-rc6 > > > > > # ./percpu_test.sh > > > > > Percpu: 1952 kB > > > > > Percpu: 219648 kB > > > > > Percpu: 219648 kB > > > > > > > > > > 5.12-rc6 + with patchset applied > > > > > # ./percpu_test.sh > > > > > Percpu: 2080 kB > > > > > Percpu: 219712 kB > > > > > Percpu: 72672 kB > > > > > > > > > > I'm able to see improvement comparable to that of what you're see too. > > > > > > > > > > However, on POWERPC I'm unable to reproduce these improvements with > > > > > the patchset in the same configuration > > > > > > > > > > POWER9 KVM 4CPU:4G > > > > > Vanilla 5.12-rc6 > > > > > # ./percpu_test.sh > > > > > Percpu: 5888 kB > > > > > Percpu: 118272 kB > > > > > Percpu: 118272 kB > > > > > > > > > > 5.12-rc6 + with patchset applied > > > > > # ./percpu_test.sh > > > > > Percpu: 6144 kB > > > > > Percpu: 119040 kB > > > > > Percpu: 119040 kB > > > > > > > > > > I'm wondering if there's any architectural specific code that needs > > > > > plumbing > > > > > here? > > > > > > > > > There shouldn't be. Can you send me the percpu_stats debug output before > > > > and after? > > > I'll paste the whole debug stats before and after here. > > > 5.12-rc6 + patchset > > > -----BEFORE----- > > > Percpu Memory Statistics > > > Allocation Info: > > > > Hm, this looks highly suspicious. Here is your stats in a more compact form: > > > > Vanilla > > > > nr_alloc : 9038 nr_alloc : > > 97046 > > nr_dealloc : 6992 nr_dealloc : 94237 > > nr_cur_alloc : 2046 nr_cur_alloc : 2809 > > nr_max_alloc : 2178 nr_max_alloc : 90054 > > nr_chunks : 3 nr_chunks : 11 > > nr_max_chunks : 3 nr_max_chunks : 47 > > min_alloc_size : 4 min_alloc_size : 4 > > max_alloc_size : 1072 max_alloc_size : 1072 > > empty_pop_pages : 5 empty_pop_pages : 29 > > > > > > Patched > > > > nr_alloc : 9040 nr_alloc : > > 97048 > > nr_dealloc : 6994 nr_dealloc : 95002 > > nr_cur_alloc : 2046 nr_cur_alloc : 2046 > > nr_max_alloc : 2208 nr_max_alloc : 90054 > > nr_chunks : 3 nr_chunks : 48 > > nr_max_chunks : 3 nr_max_chunks : 48 > > min_alloc_size : 4 min_alloc_size : 4 > > max_alloc_size : 1072 max_alloc_size : 1072 > > empty_pop_pages : 12 empty_pop_pages : 61 > > > > > > So it looks like the number of chunks got bigger, as well as the number of > > empty_pop_pages? This contradicts to what you wrote, so can you, please, > > make > > sure that the data is correct and we're not messing two cases? > > > > So it looks like for some reason sidelined (depopulated) chunks are not > > getting > > freed completely. But I struggle to explain why the initial empty_pop_pages > > is > > bigger with the same amount of chunks. > > > > So, can you, please, apply the following patch and provide an updated > > statistics? > > Unfortunately, I'm not completely well versed in this area, but yes the empty > pop pages number doesn't make sense to me either. > > I re-ran the numbers trying to make sure my experiment setup is sane but > results remain the same. > > Vanilla > nr_alloc : 9040 nr_alloc : 97048 > nr_dealloc : 6994 nr_dealloc : 94404 > nr_cur_alloc : 2046 nr_cur_alloc : 2644 > nr_max_alloc : 2169 nr_max_alloc : 90054 > nr_chunks : 3 nr_chunks : 10 > nr_max_chunks : 3 nr_max_chunks : 47 > min_alloc_size : 4 min_alloc_size : 4 > max_alloc_size : 1072 max_alloc_size : 1072 > empty_pop_pages : 4 empty_pop_pages : 32 > > With the patchset + debug patch the results are as follows: > Patched > > nr_alloc : 9040 nr_alloc : 97048 > nr_dealloc : 6994 nr_dealloc : 94349 > nr_cur_alloc : 2046 nr_cur_alloc : 2699 > nr_max_alloc : 2194 nr_max_alloc : 90054 > nr_chunks : 3 nr_chunks : 48 > nr_max_chunks : 3 nr_max_chunks : 48 > min_alloc_size : 4 min_alloc_size : 4 > max_alloc_size : 1072 max_alloc_size : 1072 > empty_pop_pages : 12 empty_pop_pages : 54 > > With the extra tracing I can see 39 entries of "Chunk (sidelined)" > after the test was run. I don't see any entries for "Chunk (to depopulate)" > > I've snipped the results of slidelined chunks because they went on for ~600 > lines, if you need the full logs let me know.
Yes, please! That's the most interesting part!
