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https://issues.apache.org/jira/browse/HADOOP-19229?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17912094#comment-17912094
]
ASF GitHub Bot commented on HADOOP-19229:
-----------------------------------------
steveloughran commented on code in PR #7281:
URL: https://github.com/apache/hadoop/pull/7281#discussion_r1911039014
##########
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/Sizes.java:
##########
@@ -0,0 +1,94 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.io;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+
+/**
+ * Sizes of binary values and other some common sizes.
+ * This avoids having to remember the larger binary values,
+ * and stops IDEs/style checkers complaining about numeric
+ * values in source code.
+ */
+@InterfaceAudience.Public
+@InterfaceStability.Evolving
+public final class Sizes {
+
+ /** 2^8 bytes: {@value}. */
+ public static final int S_256 = 256;
+
+ /** 2^9 bytes: {@value}. */
+ public static final int S_512 = S_256 << 1;
+
+ /** 2^10 bytes - 1 KiB: {@value}. */
+ public static final int S_1K = S_512 << 1;
+
+ /** 2^11 bytes - 1 KiB: {@value}. */
+ public static final int S_2K = S_1K << 1;
+
+ /** 2^12 bytes - 2 KiB: {@value}. */
+ public static final int S_4K = S_2K << 1;
+
+ /** 2^13 bytes: {@value}. */
+ public static final int S_8K = S_4K << 1;
+
+ /** 2^14 bytes: {@value}. */
+ public static final int S_16K = S_8K << 1;
+
+ /** 2^15 bytes: {@value}. */
+ public static final int S_32K = S_16K << 1;
+
+ /** 2^16 bytes: {@value}. */
+ public static final int S_64K = S_32K << 1;
+
+ /** 2^17 bytes, 128 KiB: {@value}. */
+ public static final int S_128K = S_64K << 1;
+
+ /** 2^18 bytes, 256 KiB: {@value}. */
+ public static final int S_256K = S_128K << 1;
+
+ /** 2^19 bytes, 512 KiB: {@value}. */
+ public static final int S_512K = S_256K << 1;
+
+ /** 2^20 bytes, 1 MiB: {@value}. */
+ public static final int S_1M = S_512K << 1;
+
+ /** 2^21 bytes, 2 MiB: {@value}. */
+ public static final int S_2M = S_1M << 1;
+
+ /** 2^22 bytes, 4 MiB: {@value}. */
+ public static final int S_4M = S_2M << 1;
+
+ /** 2^23 bytes, MiB: {@value}. */
+ public static final int S_8M = S_4M << 1;
+
+ /** 2^24 bytes, MiB: {@value}. */
+ public static final int S_16M = S_8M << 1;
+
+ /** 2^25 bytes, MiB: {@value}. */
+ public static final int S_32M = S_16M << 1;
+
+ /** 5 MiB: {@value}. */
+ public static final int S_5M = 5 * S_1M;
+
+ /** 10 MiB: {@value}. */
+ public static final int S_10M = 10 * S_1M << 1;
Review Comment:
yeah. got overexcited about using the operator after so long.
never used <<= >>= or even ^=
came close to using the last one once and realised it was wrong. Nothing
people would expect to see. It is used in some of the compression classes, FWIW.
> Vector IO on cloud storage: what is a good minimum seek size?
> -------------------------------------------------------------
>
> Key: HADOOP-19229
> URL: https://issues.apache.org/jira/browse/HADOOP-19229
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/s3
> Affects Versions: 3.4.1
> Reporter: Steve Loughran
> Assignee: Steve Loughran
> Priority: Major
> Labels: pull-request-available
>
> vector iO has a max size to coalesce ranges, but it also needs a maximum gap
> between ranges to justify the merge. Right now we could have a read where two
> vectors of size 8 bytes can be merged with a 1 MB gap between them -and
> that's wasteful.
> We could also consider an "efficiency" metric which looks at the ratio of
> bytes-read to bytes-discarded. Not sure what we'd do with it, but we could
> track it as an IOStat
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