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杂七杂八的,随手记录。

gpdb memory control

TODO 1 VMem

2 Resource Group Control

  • ResourceGroupGetQueryMemoryLimit(void) 用于获取内存限制的绝对大小 (非百分比)

2.1 Bypass

  • 绕开资源限制模式

  • Enabled when:

    • gp_resource_group_bypass is true: guc_gp.c

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      {
          {"gp_resource_group_bypass", PGC_USERSET, RESOURCES,
              gettext_noop("If the value is true, the query in this session will not be limited by resource group."),
              NULL
          },
          &gp_resource_group_bypass,
          false,
          check_gp_resource_group_bypass, NULL, NULL
      }
      
    • Or command is one of:

GPDB: Configuring Your Systems

本文为摘录(或转载),侵删,原文为: https://docs.vmware.com/en/VMware-Tanzu-Greenplum/6/greenplum-database/GUID-install_guide-prep_os.html

1 IP Fragmentation Settings

IP Fragmentation Settings

When the Greenplum Database interconnect uses UDP (the default), the network interface card controls IP packet fragmentation and reassemblies.

If the UDP message size is larger than the size of the maximum transmission unit (MTU) of a network, the IP layer fragments the message. (Refer to Networking later in this topic for more information about MTU sizes for Greenplum Database.) The receiver must store the fragments in a buffer before it can reorganize and reassemble the message.

Greenplum 资源管理——Resource Group使用和实现分析

Hash Index of PG

Table of Contents

本文为摘录(或转载),侵删,原文为: ../../../Work/pg_master/src/backend/access/hash/README

1 Hash Indexing

这个目录包含了 Postgres 的散列索引实现。其中大部分核心思想来自于 Margo Seltzer 和 Ozan Yigit 在 1991 年 1 月举行的冬季 USENIX 会议上的论文《A New Hashing Package for UNIX》。我们的内存哈希表实现(src/backend/utils/hash/dynahash.c)也依赖于相同的概念;它源自于 Esmond Pitt 编写的代码,后来又由 Margo 和其他人进行了改进。

How To Use Journalctl to View and Manipulate Systemd Logs

本文为摘录(或转载),侵删,原文为: https://www.digitalocean.com/community/tutorials/how-to-use-journalctl-to-view-and-manipulate-systemd-logs

1 Basic Log Viewing

要查看 journald 守护程序收集的日志,请使用 journalctl 命令。

当单独使用时,系统中的每个日志条目都会在翻页器(通常是 less)中显示,供您浏览。最旧的条目将显示在顶部: