Re: Introduction

[Evgeny Kotsuba]

On Fri, 29 Apr 2005 11:16:23 +0200
 Serassio Guido <[EMAIL PROTECTED]> wrote:
Hi Evgeny,
At 09.52 29/04/2005, Evgeny Kotsuba wrote:
FD_READ_METHOD/FD_WRITE_METHOD macros should be more efficient.
Look here:
http://cvs.sourceforge.net/viewcvs.py/squid/squid/src/fd.c?rev=1.7.16.9&only_with_tag=nt-2_5&view=auto
I don't understand  why macros may be more   efficient.
I use things like
int squid_fde::read(char *buf, int len)
{  int rc=-1;
   switch(type)
   {  case FD_SOCKET:
          if(fh < 0)
          {  debug(91, 0) ("squid_fde::read WARNING: fh=%i\n",fh);
             rc = -1;
             break;
          }
         rc = recv(fh, buf, len, 0 /* MSG_DONTWAIT ? */);
          break;
      case FD_NONE:
             fatalf("Attempt to Read with FD_NONE type handle %i 
bytes", 
len);
           return -1;
      case FD_PIPE:
      case FD_PIPE_READ:
          rc = ::read(fh, buf, len);
          break;
      default:
          rc = ::read(fh, buf, len);
  }
  if(rc>0) bytes_read += rc;
  return rc;
}
Your code is more bigger and long, for any I/O you do:
- a function call with stack and context switch (your function seems 
to be not inlined)
- a fd_table lookup
- a decision
- call to the correct I/O function.

Macros are defined in squid.h as:
#define FD_READ_METHOD(fd, buf, len) (*fd_table[fd].read_method)(fd, 
buf, len)
#define FD_WRITE_METHOD(fd, buf, len) 
(*fd_table[fd].write_method)(fd, buf, len)

read_method and write_method pointers are initialized during fd_open
Everywher in the 2.5 and 3.0 source code you find already only the 
FD_READ_METHOD/FD_WRITE_METHOD macros instead of read() and write().

Whith macros for any I/O we do:
- a fd_table lookup for the function pointer
- call to the correct I/O function with the previous pointer
More faster.
You make me laugh.  squid2.5  use  read/write/send/recv/ etc.  as well 
as FD_READ_METHOD/FD_WRITE_METHOD.
It seems the same things are in squid3.
With   classes we have only read/write/open/close  to any handle  and 
can control   it in single place.
Why you don't see "bytes_read += rc;"  that is  fd_bytes()  and that 
is one more  function call etc.  ?

 
SY,
Evgeny Kotsuba