Tag:Memory size

  • Mongodb memory usage too high


    Official documentation on memory usage https://docs.mongodb.com/v4.2… Starting from mongodb 3.4, the maximum memory occupied is: (computer memory – 1 / 2) Starting in MongoDB 3.4, the default WiredTiger internal cache size is the larger of either: 50% of (RAM – 1 GB), or256 MB. For example, my computer has 16g memory. Mongodb will occupy 7.5GB […]

  • Learn a Linux command every day (112): vmstat


    Command introduction The vmstat command is used for virtual memory statistics. Vmstat reports information about processes, memory, paging, block IO, traps, disks, and CPU activity. Syntax format vmstat [options] [delay [count]] Option description -A # show active inner page -F # displays the total number of processes created since startup -M # display slab information […]

  • What does arraysize mean?


    Send to client in. Another related parameter is SDU (session data unit). The memory size occupied by prefetching in PGA is related to the SDU size. The default is 8K SQL> show arraysize arraysize 15 SQL> create table jason as select * from dba_objects; Table created. SQL> SQL> SQL> select count(1) from dba_objects; COUNT(1) ———- […]

  • Understanding objects in Objective-C


    This article is published to personal blog synchronously. For a better reading experience, please visit here OC is a superset of C language, which provides object-oriented capability. But what is our Object-Oriented Object in OC, or how does it behave in memory? Today, let’s talk about Tao. Object understanding First, solve the problem of what […]

  • What is the method to get the runtime instance in the Java virtual machine?


    The runtime class is used to represent the running state of the Java virtual machine. It is used to encapsulate the Java virtual machine process. Every time you use the “Java” command to start the Java virtual machine, there will be a runtime instance, and there is only one instance. The application will be connected […]

  • Postgre database optimization


    1、 View server configuration 1. View the number of CPUs cat /proc/cpuinfo |grep “physical id” |sort |uniq |wc -l 2. View the number of physical cores of a single CPU cat /proc/cpuinfo |grep “cpu cores” |uniq 3. View logical threads cat /proc/cpuinfo |grep “processor” |wc -l 4. View memory size free 5. View storage size […]

  • [Linux] 2 install Linux operating system (super detailed version)


    Download from CentOS official website: http://isoredirect.centos.org/centos/7/isos/x86_64/CentOS-7-x86_64-DVD-1810.iso Click create new virtual machine and selectCustom (Advanced), and then click next; The default setting is good. Click “next”; Select “install the operating system later” and click “next”; Select “Linux” and “CentOS 7 64 bit” as the version. You can also select other versions according to your needs. Click […]

  • Redis source code series (1)


    Redis source code series memory management Function prototypesrc/zmalloc.h Function pointer andvoid*Pointer provides a generic mechanism /*stringfication*/ #define __xstr(s) __str(s) #define __str(s) #s /*prototypes*/ void *zmalloc(size_t size); void *zcalloc(size_t size); void *zrealloc(void *ptr, size_t size); void zfree(void *ptr); char *zstrdup(const char *s); size_t zmalloc_used_memory(void); void zmalloc_enable_thread_safeness(void); void zmalloc_set_oom_handler(void (*oom_handler)(size_t)); float zmalloc_get_fragmentation_ratio(size_t rss); size_t zmalloc_get_rss(void); #ifndef HAVE_MALLOC_SIZE […]

  • Interviewer: redis memory data is full, will it go down?


    background Redis database memory full, will it go down? The answer is: it will not be full. When using redis, we need to configure the maximum memory size that redis can use. When the storage reaches a certain capacity, there are redis’s memory elimination strategies, LRU algorithm elimination, and so on. Redis’s memory elimination strategy […]

  • The growth factor of vector in C + +


    We all know what C + + doesvectorThe capacity of will increase automatically with the added elements, but how much does it increase each time? Twice the original? triple? Or how much? Next, let’s study how the growth factor is determined. First of all, I want to elaborate a problemvectorRealization related facts:vectoruseallocatorInstead ofreallocSo, no matter […]

  • test2


    Test2 new to fwq 1. Setting – XMS = – Xmx goes without saying 2. The initial heap memory allocated by the JVM is specified by – XMS, which is 1 / 64 of the physical memory by default; the maximum heap memory allocated by the JVM is specified by – Xmx, which is 1 […]

  • Shell one click configuration of single instance Oracle basic environment variables (linux7)


    #!/bin/bash Echo “modify host name” hostnamectl set-hostname wangxfa hostname sleep 1 Echo “view and close firewall” systemctl status firewalld systemctl stop firewalld systemctl disable firewalld systemctl status firewalld sleep 1 Echo “disable SELinux” sed -i “s/SELINUX=enforcing/SELINUX=disabled/g” /etc/selinux/config #add user and group Echo “create users and groups needed to install oracle” groupadd -g 1030 oinstall groupadd […]