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    <p>I'll share my reduced assembly knowledge with you:</p> <pre><code>61 TEXT ·RawSyscall(SB),7,$0 62 MOVQ 16(SP), DI 63 MOVQ 24(SP), SI 64 MOVQ 32(SP), DX 65 MOVQ $0, R10 66 MOVQ $0, R8 67 MOVQ $0, R9 68 MOVQ 8(SP), AX // syscall entry 69 ADDQ $0x2000000, AX 70 SYSCALL 71 JCC ok1 72 MOVQ $-1, 40(SP) // r1 73 MOVQ $0, 48(SP) // r2 74 MOVQ AX, 56(SP) // errno 75 RET 76 ok1: 77 MOVQ AX, 40(SP) // r1 78 MOVQ DX, 48(SP) // r2 79 MOVQ $0, 56(SP) // errno 80 RET 81 </code></pre> <ul> <li>Line 61 is the routine entry point</li> <li>Line 76 is a label called <code>ok1</code></li> <li>Line 71 is a conditional jump to label <code>ok1</code>.</li> </ul> <p>The short names you see on every line on the left side are called <code>mnemonics</code> and stand for assembly instructions:</p> <ul> <li><code>MOVQ</code> means Move Quadword (64 bits of data).</li> <li><code>ADDQ</code> is Add Quadword.</li> <li><code>SYSCALL</code> is kinda obvious</li> <li><code>JCC</code> is Jump if Condition (condition flag set by previous instruction)</li> <li><code>RET</code> is return</li> </ul> <p>On the right side of the mnemonics you'll find each instruction's arguments which are basically constants and <a href="http://tanmayonrun.blogspot.ch/2011/06/purposes-of-having-general-registers.html" rel="noreferrer">registers</a>.</p> <ul> <li><code>SP</code> is the Stack Pointer</li> <li><code>AX</code> is the Accumulator</li> <li><code>BX</code> is the Base register</li> </ul> <p>each register can hold a certain amount of data. On 64 bit CPU architectures I believe it's in fact 64 bits per register.</p> <p>The only difference between <code>Syscall</code> and <code>RawSyscall</code> is on line 14, 28 and 34 where <code>Syscall</code> will call <code>runtime·entersyscall(SB)</code> and <code>runtime·exitsyscall(SB)</code> whereas <code>RawSyscall</code> will not. I assume this means that <code>Syscall</code> notifies the runtime that it's switched to a blocking syscall operations and can yield CPU-time to another goroutine/thread whereas <code>RawSyscall</code> will just block.</p>
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    1. COThank for quick reply, so is that mean programmers should use `Syscall` in non-blocking situations and `RawSyscall` in blocking situations?
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    2. COI think user-level code should always use `Syscall` whereas `RawSyscall` exists for very specific situations.
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