文件名称：zero copy(kafka)
文件大小：208KB
文件格式：PDF
更新时间：2020-12-06 09:35:05
zero copy kafka
Efficient data transfer through zero copy 1、The read() call causes a context switch (see Figure 2) from user mode to kernel mode. Internally a sys_read() (or equivalent) is issued to read the data from the file. The first copy (see Figure 1) is performed by the direct memory access (DMA) engine, which reads file contents from the disk and stores them into a kernel address space buffer. 2、The requested amount of data is copied from the read buffer into the user buffer, and the read() call returns. The return from the call causes another context switch from kernel back to user mode. Now the data is stored in the user address space buffer. 3、The send() socket call causes a context switch from user mode to kernel mode. A third copy is performed to put the data into a kernel address space buffer again. This time, though, the data is put into a different buffer, one that is associated with the destination socket. 4、The send() system call returns, creating the fourth context switch. Independently and asynchronously, a fourth copy happens as the DMA engine passes the data from the kernel buffer to the protocol engine.