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From "Dan Hecht (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-3202: DiskIoMgr improvements for new buffer pool
Date Tue, 25 Oct 2016 20:53:10 GMT
Dan Hecht has posted comments on this change.

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


Patch Set 1:

(8 comments)

http://gerrit.cloudera.org:8080/#/c/4631/1/be/src/exec/hdfs-scan-node-base.h
File be/src/exec/hdfs-scan-node-base.h:

PS1, Line 193: BufferOpts
const& ?


http://gerrit.cloudera.org:8080/#/c/4631/1/be/src/runtime/disk-io-mgr.cc
File be/src/runtime/disk-io-mgr.cc:

PS1, Line 642: without the client providing a "
             :           "buffer"
is this going to make sense to a user?


Line 708:   DCHECK_LE(buffer_size, max_buffer_size_);
how do we ensure this is true? is it the check in DiskIoMgr::Read() that will always enforce?


http://gerrit.cloudera.org:8080/#/c/4631/1/be/src/runtime/disk-io-mgr.h
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:

... these buffers are wrapped in BufferDescriptors and return to the caller.


Line 150: /// another read. In error cases, the IoMgr will recycle the buffers more promptly
but
is this relevant for all cases, or only cases (a) and (b)?


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


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 that it's another
possible source of the buffer.  Alternatively, consider even making a union to make it clear
that they are mutually exclusive, and the union tag indicates the buffer "mode" (Managed,
HdfsCached, Client - or something like that).  Though it could be that doesn't work out cleanly
given that HdfsCached can fallback to Managed mode.


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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 <tarmstrong@cloudera.com>
Gerrit-Reviewer: Dan Hecht <dhecht@cloudera.com>
Gerrit-Reviewer: Michael Ho
Gerrit-HasComments: Yes

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