On Mon, Jan 29, 2018 at 1:34 AM, Chintan Pandya <cpandya@xxxxxxxxxxxxxx> wrote: > >> I was curious, so I implemented it. It ends up being similar to Rasmus's >> 1st suggestion. The difference is we don't try to store all entries, but >> rather implement a hash table that doesn't handle collisions. Relying on >> the fact that phandles are just linearly allocated from 0, we just mask >> the high bits of the phandle to get the index. > > I think this is most resourceful way. >> >> Can you try out on your setup and try different >> array sizes. > > Here are my test results. However, I simply considered overall boot time to > compare different scenarios because profiling of_find_node_by_phandle() in > early boot fails. > > Scenarios: > [1] Cache size 1024 + early cache build up [Small change in your cache > patch, > see the patch below] > [2] Hash 64 approach[my original v2 patch] > [3] Cache size 64 > [4] Cache size 128 > [5] Cache size 256 > [6] Base build > > Result (boot to shell in sec): > [1] 14.292498 14.370994 14.313537 --> 850ms avg gain > [2] 14.340981 14.395900 14.398149 --> 800ms avg gain > [3] 14.546429 14.488783 14.468694 --> 680ms avg gain > [4] 14.506007 14.497487 14.523062 --> 670ms avg gain > [5] 14.671100 14.643344 14.731853 --> 500ms avg gain It's strange that bigger sizes are slower. Based on this data, I'd pick [3]. How many phandles do you have? I thought it was hundreds, so 1024 entries would be more than enough and you should see some curve to a max gain as cache size approaches # of phandles. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
