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From Neil Conway <neil.con...@gmail.com>
Subject Re: Review Request 57254: Added support for hierarchical roles to DRFSorter.
Date Mon, 17 Apr 2017 16:21:17 GMT


> On April 17, 2017, 3:09 p.m., Jay Guo wrote:
> > src/master/allocator/sorter/drf/sorter.cpp
> > Line 333 (original), 509 (patched)
> > <https://reviews.apache.org/r/57254/diff/17/?file=1692350#file1692350line536>
> >
> >     In case of `dirty`, how about insert logic of `listClients` there to avoid traversing
tree twice for the sake of performance? I tried a benchmark test which does suggest a performance
benefit.

That could be a useful improvement. When you benchmarked this, what % performance improvement
did you observe?


- Neil


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On April 13, 2017, 9:42 p.m., Neil Conway wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/57254/
> -----------------------------------------------------------
> 
> (Updated April 13, 2017, 9:42 p.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/17/
> 
> 
> Testing
> -------
> 
> 
> Thanks,
> 
> Neil Conway
> 
>


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