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杂七杂八的,随手记录。

100x Faster Query in Aurora Postgres with a lower random_page_cost

本文为摘录(或转载),侵删,原文为: https://postgr.es/p/6oe

最近我在 Postgres 中处理一些查询,发现它要么选择不使用索引执行顺序扫描,要么选择使用复合部分索引的替代索引。这让我感到困惑,尤其是知道系统中有可以更快执行这些查询的索引时。

HashData|产品介绍

本文为摘录(或转载),侵删,原文为: https://docs.hashdata.xyz/docs/20-product-guide/

1 Abort HashData

HashData was founded in 2016 by the guys who built Apache HAWQ, one of the most advanced SQL on Hadoop solutions. As the flagship product of the company, HashData Warehousing is a data warehouse service built for the cloud. While 100% compatible with the analytics interfaces of the open source MPP database Greenplum,HashData’s unique architecture delivers proven breakthroughs in performance, concurrency, elasticity and simplicity.

How can 3ware and MegaRAID performance be increased in Linux?

本文为摘录(或转载),侵删,原文为: https://www.broadcom.com/support/knowledgebase/1211161453667/how-can-3ware-and-megaraid-performance-be-increased-in-linux

1 Question

How can LSI 3ware and LSI MegaRAID performance be increased in Linux?

2 Answer

2.1 For the Linux 2.6 kernel:

See KB article A004958 Article ID 1211161457978 See also: Article ID 1211161479669

Linux内核机制—spin_lock (转载)

本文为摘录(或转载),侵删,原文为: https://www.cnblogs.com/hellokitty2/p/16368024.html

1 pin_lock 概述

  1. spin lock 是一种不可休眠锁,可用于原子上下文。当获取不到锁的时候会 spin 等待,此时是 running 状态。

A Close Look at a Spinlock – Embedded in Academia

本文为摘录(或转载),侵删,原文为: https://blog.regehr.org/archives/2173

自旋锁 (spinlock) 是多处理器操作系统提供的最基本的互斥原语。自旋锁需要保护当前 CPU 免受抢占(通常通过禁用中断,但我们会在本文中忽略这个方面),并且还需要防止其他核心同时访问临界区(通过使用原子内存操作)。正如其名称所示,尝试获取已锁定的自旋锁会简单地自旋:它们会消耗 CPU 时间: