Add a quick FAQ.

FAQ.md

@@ -0,0 +1,77 @@
+# A quick tracy FAQ
+
+### I already use VTune/perf/Very Sleepy/callgrind/MSVC profiler.
+
+These are statistical profilers, which can be used to find hot spots in the code. This is very useful, but it won't show you the underlying reason for semi-random frame stutter that may occur every couple of seconds.
+
+### You can use Telemetry for that.
+
+Telemetry license costs about 8000 $ per year. Tracy is open source software. Telemetry doesn't have Lua bindings.
+
+### You can use the free Brofiler. Crytek does use it, so it has to be good.
+
+After a cursory look at the Brofiler code I can tell that the timer resolution there is at 300 ns. Tracy can achieve 5 ns timer resolution. Brofiler event logging infrastructure seems to be over-engineered. Brofiler can't track lock contention, nor does it have Lua bindings.
+
+### So tracy is supposedly faster?
+
+My measurements show that logging a single zone with tracy takes only 15 ns. In theory, if the program was doing nothing else, tracy should be able to log 66 million zones per second.
+
+### Bullshit, RAD is advertising that they are able only to log about a million zones, over the network nevertheless: "Capture over a million timing zones per second in real-time!"
+
+Tracy can perform network transfer of 15 million zones per second. Should the client and server be on separate machines, this number will be even higher, but you will need more than a gigabit link to achieve the maximum throughput. [Click here for a video of a max-throughput capture.](https://www.youtube.com/watch?v=DSMIHShKGAc)
+
+### Can I connect to my application at any time and start profiling at this moment?
+
+No, all events are registered from the beginning of program execution and are waiting in a queue.
+
+### Am I seeing correctly that the profiler allocates one gigabyte of memory per second?
+
+Only in extreme cases. Normal usage has much lower memory pressure.
+
+### Why do you do magic with the static initialization order? Everyone says that's a bad practice.
+
+It allows tracking construction of static objects and memory allocations performed before main() is entered.
+
+### There's no support for consoles.
+
+Welp. But there's mobile support.
+
+### I do need console support.
+
+The code is open. Write your own, then send a patch.
+
+### I don't believe you can capture a zone in 15 ns. Show me the code!
+
+Following is the annotated assembly code (generated from C++ sources) that's responsible for logging start of the zone:
+
+```
+call        qword ptr [__imp_GetCurrentThreadId]
+mov         r14d,eax
+mov         qword ptr [rsp+0F0h],r14        // save thread id for later use
+mov         r12d,10h
+mov         rax,qword ptr gs:[58h]          // TLS
+mov         r15,qword ptr [rax]             // queue address
+mov         rdi,qword ptr [r12+r15]         // data address
+mov         rbp,qword ptr [rdi+20h]         // buffer counter
+mov         rbx,rbp
+and         ebx,7Fh                         // 128 item buffer
+jne         Application::InnerLoop+66h --+
+mov         rdx,rbp                      |
+mov         rcx,rdi                      |
+call        enqueue_begin_alloc          |  // reclaim/alloc next buffer
+shl         rbx,5  <---------------------+  // buffer items are 32 bytes
+add         rbx,qword ptr [rdi+40h]
+mov         byte ptr [rbx],4                // queue item type
+rdtscp
+mov         dword ptr [rbx+19h],ecx         // cpu id
+shl         rdx,20h
+or          rax,rdx                         // 64 bit timestamp
+mov         qword ptr [rbx+1],rax
+mov         qword ptr [rbx+9],r14           // thread id
+lea         rax,[__tracy_source_location]   // static struct address
+mov         qword ptr [rbx+11h],rax
+lea         rax,[rbp+1]                     // increment buffer counter
+mov         qword ptr [rdi+20h],rax
+```
+
+There's also a second code block, for the end of the zone. It's similar, but a bit smaller, as it can use some of the variables that were retrieved above.

README.md

@@ -20,6 +20,8 @@ The following compilers are supported:
 - gcc
 - clang
 
+[A quick FAQ.](FAQ.md)
+
 ### High-level overview
 
 ![](doc/design.svg)