> On April 20, 2017, 9:35 a.m., Michael Park wrote: > > src/master/allocator/sorter/drf/sorter.hpp > > Line 263 (original), 380 (patched) > > <https://reviews.apache.org/r/57254/diff/19/?file=1693589#file1693589line482> > > > > `s/DRFComparator/compare/`? > > > > We typically name the parameters `left` and `right`
Personally I like `DRFComparator` more: it makes it clear that the function is comparing the two nodes according to DRF. I renamed the parameters. > On April 20, 2017, 9:35 a.m., Michael Park wrote: > > src/master/allocator/sorter/drf/sorter.cpp > > Line 74 (original), 108-116 (patched) > > <https://reviews.apache.org/r/57254/diff/19/?file=1693590#file1693590line109> > > > > There are `nameElements` and `element` here rather than > > `elements/element` or `nameElements/nameElement`. I think we also used > > `components/component` in `quotaHandler`. Maybe it'd be better to stick > > with that naming scheme? I renamed `name` to `clientPath` and used `pathElements`/`element`, which seems OK to me. > On April 20, 2017, 9:35 a.m., Michael Park wrote: > > src/master/allocator/sorter/drf/sorter.cpp > > Lines 117-125 (patched) > > <https://reviews.apache.org/r/57254/diff/19/?file=1693590#file1693590line118> > > > > I think this would be cleaner to say: > > ```cpp > > auto iter = std::find_if( > > current->children.begin(), > > current->children.end(), > > [&](const Node* child) { return child->name == element; }); > > > > if (iter != current->children.end()) { > > current = *iter; > > continue; > > } > > > > /* ... */ > > ``` Happy to discuss further, but this seems more difficult to read, personally. I feel like we usually use an explicit `foreach` loop in similar situations elsewhere... > On April 20, 2017, 9:35 a.m., Michael Park wrote: > > src/master/allocator/sorter/drf/sorter.cpp > > Lines 128 (patched) > > <https://reviews.apache.org/r/57254/diff/19/?file=1693590#file1693590line129> > > > > I think the "// We didn't find `element`, so add a new child to > > `current`.` is better placed after the "leaf -> internal" if block, where > > we actually add the new child. Personally I think it is important to have a comment at the start of the `if (!found) { ... }`, to explain what the entire block is doing. I added a second comment down below, though. > On April 20, 2017, 9:35 a.m., Michael Park wrote: > > src/master/allocator/sorter/drf/sorter.cpp > > Lines 75-77 (original), 143-172 (patched) > > <https://reviews.apache.org/r/57254/diff/19/?file=1693590#file1693590line144> > > > > Kind of seems like it'd be simpler to just modify `current`. > > > > ``` > > parent->removeChild(current); > > > > // Create a node under `parent`. This internal node will become the > > new parent. > > Node* internal = new Node(current->name, parent); > > parent->addChild(internal); > > internal->allocation = current->allocation; > > CHECK_EQ(path, internal->path); > > > > // Update `current` to become the virtual leaf node. > > current->name = "."; > > current->parent = internal; > > internal->addChild(current); > > current->path = strings::join("/", parent->path, current->name); > > > > current = internal; > > ``` Happy to discuss further, but personally I prefer the current coding because it seems safer to avoid mutating an existing tree node "in place". e.g., if there were other pointers to `current` that should _not_ be updated to point to the virtual leaf node, they will now be dangling pointers (i.e., clearly wrong) rather than now silently pointing at the virtual leaf node. > On April 20, 2017, 9:35 a.m., Michael Park wrote: > > src/master/allocator/sorter/drf/sorter.cpp > > Line 155 (original), 328 (patched) > > <https://reviews.apache.org/r/57254/diff/19/?file=1693590#file1693590line341> > > > > ``` > > for (Node* current = CHECK_NOTNULL(find(name)); > > current != root; > > current = CHECK_NOTNULL(current->parent)) > > ``` > > > > Other similar situations below. IMO the current coding is more readable, but happy to discuss further if you disagree. - Neil ----------------------------------------------------------- This is an automatically generated e-mail. To reply, visit: https://reviews.apache.org/r/57254/#review172425 ----------------------------------------------------------- On April 20, 2017, 12:10 a.m., Neil Conway wrote: > > ----------------------------------------------------------- > This is an automatically generated e-mail. To reply, visit: > https://reviews.apache.org/r/57254/ > ----------------------------------------------------------- > > (Updated April 20, 2017, 12:10 a.m.) > > > Review request for mesos, Benjamin Bannier, Benjamin Mahler, and Michael Park. > > > Repository: mesos > > > Description > ------- > > This commit replaces the sorter's flat list of clients with a tree; the > tree represents the hierarchical relationship between sorter clients. > Each node in the tree contains a vector of pointers to child nodes. The > tree might contain nodes that do not correspond directly to sorter > clients. For example, adding clients "a/b" and "c/d" results in the > following tree: > > root > -> a > -> b > -> c > -> d > > The `sort` member function still only returns one result for each active > client in the sorter. This is implemented by ensuring that each sorter > client is associated with a leaf node in the tree. Note that it is > possible for a leaf node to be transformed into an internal node by a > subsequent insertion; to handle this case, we "implicitly" create an > extra child node, which maintains the invariant that each client has a > leaf node. For example, if the client "a/b/x" is added to the tree > above, the result is: > > root > -> a > -> b > -> . > -> x > -> c > -> d > > The "." leaf node holds the allocation that has been made to the "a/b" > client itself; the "a/b" node holds the sum of all the allocations that > have been made to the subtree rooted at "a/b", which also includes > "a/b/x". > > This commit also introduces a new approach to sorting: rather than > keeping an `std::set` of sorter clients, we now keep a tree of > `std::vector`, which is sorted explicitly via `std::sort`. The previous > implementation tried to optimize the sorting process by updating the > sort order incrementally when a single sorter client was updated; this > commit removes that optimization, and instead re-sorts the entire tree > whenever the sort order is changed. > > Re-introducing a version of this optimization would make sense in the > future (MESOS-7390), but benchmarking suggests that this commit results > in a net improvement in sorter performance anyway. The sorter perf > improvement is likely due to the introduction of a secondary hashmap > that allows the leaf node associated with a tree path to be find > efficiently; the previous implementation required a linear scan of a > `std::set`. > > > Diffs > ----- > > src/master/allocator/sorter/drf/metrics.cpp > 15aab32db5ca1a7a14080e9bbb7c65283be3ec20 > src/master/allocator/sorter/drf/sorter.hpp > 76329220e1115c1de7810fb69b943c78c078be59 > src/master/allocator/sorter/drf/sorter.cpp > ed54680cecb637931fc344fbcf8fd3b14cc24295 > src/master/allocator/sorter/sorter.hpp > b3029fcf7342406955760da53f1ae736769f308c > src/tests/hierarchical_allocator_tests.cpp > 33e7b455f8664858eb4f03727b076a10c80cd6e0 > src/tests/master_allocator_tests.cpp > 119e318f8a01d50e8dae5c30cf5fa6a017c3c625 > src/tests/sorter_tests.cpp 43bd85798aef0c89751b725ebf35308a5e9e997a > > > Diff: https://reviews.apache.org/r/57254/diff/20/ > > > Testing > ------- > > > Thanks, > > Neil Conway > >
