摘要：本文测试时间时2020.12.06 测试的mysql版本是community版本8.0.22 首先指出一个select ...for update的一个大家很容易产生的错误理解："for update可以锁存在的和不存在的记录，同一个索引字段的同样的值一定会block住。" 这句话对也不对。对是指它 阅读全文

摘要：First confirm that you have root privilege. Second check the config of kernel that you have the configs on: Last you confirm you have your debugfs/tra 阅读全文

摘要：mutex( x lock): when a mutex lock is obtained, others cannot obtain the same mutex while the lock is not freed. shared lock( s lock): when a shared lo 阅读全文

摘要：libev First let's talk about libev, it is a lib used in ss. The coding style of libev is ugly. To see man page of libev by: man ./ev.3 3 files need to 阅读全文

摘要：SACK: (selective ack), it is an option added to normal ack packets. Normally sack can specify at most 4 groups of seq_start, seq_end. Meaning bytes at 阅读全文

摘要：How the algorithm and formula are implemented seem trivial, the most important of the passage's idea is the definition of 'conservation of packets'. F 阅读全文

摘要：At kernel init, each logical core has a thread called ksoftirq/%d running. These threads are brought up by the initial function net_dev_init(). While 阅读全文

摘要：According to RedHat accessories, TCP_NODELAY: each call to write(fd, buf...) will be sent out as packet. This leads to poor overall performance when m 阅读全文

摘要：In linux mm folder, there are 3 files that about kmalloc/kmem, slab/slub/slob, where slab.c defines general memory usage, slub.c defines modern memory 阅读全文

摘要：Before using stap, the kernel-debuginfo-$(uname -r), kernel-debuginfo-common-$(uname -m)-$(uname -r) and kernel-devel-$(uname -r) should be installed. 阅读全文

摘要：However till now golang's debug functionality seems far from okay. During debug you cannot print map objects. And also from debugging related aspects, 阅读全文

摘要：Before preceding, several things need to be checked: There are too many tutorials on how to build with ct-ng, I only list several useful steps for fut 阅读全文

摘要：1. malloc memory should always use the following form: 2. memset memory to 0 should use the form: 3. malloc(0) might also return address which is non- 阅读全文

摘要：Linux block devices can be partitioned into several partitions, max to several tens or hundreds primary partitions. (According to MBR or GPT) In order 阅读全文

摘要：My summary after reading this. Before doing large memory writes: _mm*_stream_s[i,s,d]*: non-temporal memory store: When data is produced and not (imme 阅读全文

摘要：Some definitive names: 1. Socket: the thing that plug into the motherboard slot; 2. Core: multiple counts of these hardware things are included in 1 c 阅读全文

摘要：ioctl is used in communication with modules of Linux. Module: User space In case of Makefile is needed: 阅读全文

摘要：some frequently used AC macros: AC_INIT :must AC_OUTPUT :must AC_PREREQ :determine ac version so that needed features are included AC_CONFIG_SRCDIR :d 阅读全文

摘要：From wiki quote: The Time Stamp Counter (TSC) is a 64-bit register present on all x86 processors since the Pentium. It counts the number of cycles sin 阅读全文

摘要：Sometimes we build a program as release and when debugging, some variables cannot be printed out, and displayed as optimized out. That is because the 阅读全文