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From "Tim Armstrong (Code Review)" <>
Subject [Impala-ASF-CR] IMPALA-3202: DiskIoMgr improvements for new buffer pool
Date Wed, 26 Oct 2016 00:32:20 GMT
Tim Armstrong has posted comments on this change.

Change subject: IMPALA-3202: DiskIoMgr improvements for new buffer pool

Patch Set 1:

File be/src/exec/hdfs-scan-node-base.h:

PS1, Line 193: BufferOpts
> const& ?
File be/src/runtime/

PS1, Line 642: without the client providing a "
             :           "buffer"
> is this going to make sense to a user?
Probably not. The old message wasn't actionable either by a user (beyond reporting the bug).
Reworded to make it clear that it's an internal error.

Line 708:   DCHECK_LE(buffer_size, max_buffer_size_);
> how do we ensure this is true? is it the check in DiskIoMgr::Read() that wi
DiskIoMgr::ReadRange() checks if there's a client buffer before calling TryAllocateNextBufferForRange().
File be/src/runtime/disk-io-mgr.h:

PS1, Line 147: these buffers are returned to the caller wrapped
             : /// in BufferDescriptors.
> took a few seconds to parse and understand. how about:
Yes that's better...

Line 150: /// another read. In error cases, the IoMgr will recycle the buffers more promptly
> is this relevant for all cases, or only cases (a) and (b)?
Tried to clarify. Also removed the last sentence since I think it was confusing and not really
useful to the reader.

PS1, Line 392: bool
> maybe make all of these members 'const' since they are "options" that don't

PS1, Line 422: BufferOpts
> const BufferOpts& ?

Line 506:     int64_t client_buffer_len_;
> maybe move this right before cached_buffer_ since it's related in the sense
Switched it to a tagged union. We don't really have much precedent in the codebase for this
pattern so I invented some conventions that made sense to me.

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Gerrit-MessageType: comment
Gerrit-Change-Id: I913fbb8ae6c242f1585992eb2a622509344dccec
Gerrit-PatchSet: 1
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Tim Armstrong <>
Gerrit-Reviewer: Dan Hecht <>
Gerrit-Reviewer: Michael Ho
Gerrit-Reviewer: Tim Armstrong <>
Gerrit-HasComments: Yes

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