[kudu-CR] WIP: release WritableLogSegment buffers when log is idle

["David Ribeiro Alves (Code Review)" <ge...@cloudera.org>]

David Ribeiro Alves has posted comments on this change.

Change subject: WIP: release WritableLogSegment buffers when log is idle
......................................................................


Patch Set 2:

(2 comments)

yeah, it'd nice to quantify how much data we're wasting on this.

http://gerrit.cloudera.org:8080/#/c/6611/2/src/kudu/consensus/log.cc
File src/kudu/consensus/log.cc:

PS2, Line 224: // TODO(todd): consider rolling to a non-preallocated segment if we are
             :       // idle for a good period of time (eg a few minutes), so that startup time is
             :       // improved and disk usage is minimized.
I forget, do all of you memstores get flushed in a time basis, no matter how small?


http://gerrit.cloudera.org:8080/#/c/6611/2/src/kudu/util/faststring-test.cc
File src/kudu/util/faststring-test.cc:

PS2, Line 18: #include <algorithm>
            : #include "kudu/util/faststring.h"
            : #include "kudu/util/random.h"
            : #include "kudu/util/random_util.h"
            : #include "kudu/util/test_util.h"
            : 
            : namespace kudu {
            : class FaststringTest : public KuduTest {};
            : 
            : TEST_F(FaststringTest, TestShrinkToFit_Empty) {
            :   faststring s;
            :   s.shrink_to_fit();
            :   ASSERT_EQ(faststring::kInitialCapacity, s.capacity());
            : }
            : 
            : TEST_F(FaststringTest, TestShrinkToFit_SmallerThanInitialCapacity) {
            :   faststring s;
            :   s.append("hello");
            :   s.shrink_to_fit();
            :   ASSERT_EQ(faststring::kInitialCapacity, s.capacity());
            : }
            : 
            : TEST_F(FaststringTest, TestShrinkToFit_Random) {
            :   Random r(GetRandomSeed32());
            :   int kMaxSize = faststring::kInitialCapacity * 2;
            :   std::unique_ptr<char[]> random_bytes(new char[kMaxSize]);
            :   RandomString(random_bytes.get(), kMaxSize, &r);
            : 
            :   faststring s;
            :   for (int i = 0; i < 100; i++) {
            :     int new_size = r.Uniform(kMaxSize);
            :     s.resize(new_size);
            :     memcpy(s.data(), random_bytes.get(), new_size);
            :     s.shrink_to_fit();
            :     ASSERT_EQ(0, memcmp(s.data(), random_bytes.get(), new_size));
            :     ASSERT_EQ(std::max<int>(faststring::kInitialCapacity, new_size), s.capacity());
            :   }
            : }
split the faststring changes?


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Gerrit-MessageType: comment
Gerrit-Change-Id: I512c7f9264ac9490e6a57259e4d7b2608adc1ca7
Gerrit-PatchSet: 2
Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-Owner: Todd Lipcon <to...@apache.org>
Gerrit-Reviewer: Adar Dembo <ad...@cloudera.com>
Gerrit-Reviewer: David Ribeiro Alves <da...@gmail.com>
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Tidy Bot
Gerrit-HasComments: Yes