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From "Tim Armstrong (Code Review)" <>
Subject [Impala-ASF-CR] IMPALA-3200: Implement suballocator for splitting buffers
Date Fri, 09 Dec 2016 20:11:46 GMT
Tim Armstrong has posted comments on this change.

Change subject: IMPALA-3200: Implement suballocator for splitting buffers

Patch Set 4:


Sorry for the slow turnaround, got caught up in things.
Commit Message:

Line 14: larger chunks. This helps avoid fragmentation and is quite effective
> I think there are a few ways to get both what I am concerned about (buddy a

I added the static_assert - that is a good idea.

I think the Atom idea is nice but I think we end up with the same problem with large buffers,
since the buffer pool only supports powers-of-two.
File be/src/bufferpool/

Line 107:   // Make allocations smaller than the buffer size.
> What happened to the const?
The const was incorrect - I pushed a patchset without the fix. The problem is that GetUsedReservation()
is a non-const method since it acquires the mutex.
File be/src/bufferpool/suballocator.h:

Line 171:   Suballocation* prev_free_;
> Just so I'm clear, in the current system, a Suballocation may have several 
Yep, that's true. I realise that it's really not obvious why the lifetime of 'buddy_' and
'prev_free_' is shorter than the unique_ptr. I documented that and then described the ownership
cases in the class header.

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Gerrit-MessageType: comment
Gerrit-Change-Id: I8bfe0e429f67ad273f7c7d0816703a9e6c3da788
Gerrit-PatchSet: 4
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Tim Armstrong <>
Gerrit-Reviewer: Jim Apple <>
Gerrit-Reviewer: Michael Ho
Gerrit-Reviewer: Michael Ho <>
Gerrit-Reviewer: Tim Armstrong <>
Gerrit-HasComments: Yes

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