inline vs define

inline通常用於作為小而短的function的修飾字，用來提示compiler這段code很少，可以考慮直接在call它的地方作展開而不用真的作為function，作為function會有functions間跳轉之stack opeartions的overhead，直接在被call的地方展開就不用這些overhead，但會造成code體積變大，或許會造成cahce hit rate下降，所以交由compiler去安排

define的話就是直接展開了

Use tar and pigz to compress things in multithread

install pigz first

and then

tar -c --use-compress-program=pigz -f <tar.filename> <dir_to_zip>

make a big file

fallocate -l 10g filename
只有分配空間

dd if=/dev/zero of=fiename bs=1M count=10240
填零填到10GB後結束

Compile QEMU in ubuntu 14.04

To compile QEMU in ubuntu 14.04, you need to download the needed libraries first

sudo apt-get install zlib1g-dev libglib2.0-dev autoconf automake libtool

If you need to browse the execution screen via a window in host instead of using VNC, you will need to install gtk.

sudo apt-get install build-essential libgtk2.0-dev libvte-dev

Then command ./configure --target-list="What you desire" --enable-gtk.

ex: ./configure --target-list="x86_64-softmmu" --enable-gtk

Then command make, and it will make the files in some directory, ex:"x86_64-softmmmu".
Btw, you can use -j8 to accelerate with 8 threads,' there is no space between 'j' and8', unlike compiling linux kernel.

pthread

除了要#include <pthread.h>
編譯的時候還要下-pthread指令

ex:gcc test.c -o test -pthread

pthread_create(pid,NULL,*void,(*void)arg);
第三項是pthread要跑的function位置，這個function只能接受一個argument傳入，限定為void type，有需求傳入多個arguments時，定一個struct把需要的arguments都包起來。可以回傳值，所以也限定為void*，因此function定義時要定成void* mydeffunc(void* arg)

ex:


void *doit(void *arg);

/*define a struct to wrap needed arguments*/
struct myDefStruct
{
struct sockaddr_in servaddr;
int sockfd;
};

/*call pthread_create的時候*/
/*when call pthread_create*/
struct myDefStruct *myDefPtr;
for ( ; ; ) {
clilen = sizeof(cliaddr);
connfd = accept(listenfd, (__SOCKADDR_ARG) &cliaddr, &clilen);
myDefPtr= (struct myDefStruct*)malloc(sizeof(struct myDefStruct));
myDefPtr->servaddr = cliaddr;
myDefPtr->sockfd = connfd;
pthread_create(&tid, NULL, &doit, (void*)myDefPtr);
 }


/*如何取出void*型別的資訊*/
/*How to retrieve the data in void* type by casting*/
void *doit(void *arg)
{
int sockfd = ((struct myDefStruct*)arg)->sockfd;
struct sockaddr_in servaddr = ((struct myDefStruct*)arg)->servaddr;
...............
}

用gcc編譯c++的檔案

要加-lstdc++指令

ex:gcc test.cc -lstdc++ -o test

unix下include math.h、cmath

在compile的時候要加上-lm的指令

ex: gcc test.c -o test -lm