RE: epoll,threading

["David Schwartz" <davids@webmaster.com>]

> In my experience, it's not much the context switch by itself which causes
> performance degradation, but the fact that with threads, you have to put
> mutexes everywhere. And frankly, walking a list with locks everywhere
> is quite slower than doing it in one run at a rate of 3 or 4 cycles per
> entry. Also, local storage in function returns is not possible anymore,
> and some functions even need to malloc() instead of returning statically
> allocated data. I believe this is the reason for openssl being twice as
> slow when compiled thread-safe than in native mode.

I don't know where you got this idea from, but several experiments of mine
failed to confirm it. Here, for example, are two identical builds of
OpenSSL, one with 'threads' and one with 'no-threads'. Same compiler, same
other flags, same hardware (Linux 2.6.21.2, P3-1Ghz):

OpenSSL 0.9.8d 28 Sep 2006
built on: Wed May 30 00:55:25 PDT 2007
options:bn(64,32) md2(int) rc4(idx,int) des(ptr,risc1,16,long) aes(partial)
idea(int) blowfish(idx)
compiler:
gcc -DDSO_DLFCN -DHAVE_DLFCN_H -mcpu=pentium -DL_ENDIAN -DTERMIO -O3 -fomit-
frame-pointer -Wall -DOPENSSL_BN_ASM_PART_WORDS -DOPENSSL_IA32_SSE2 -DSHA1_A
SM -DMD5_ASM -DRMD160_ASM -DAES_ASM
available timing options: TIMES TIMEB HZ=100 [sysconf value]
timing function used: times
The 'numbers' are in 1000s of bytes per second processed.
type             16 bytes     64 bytes    256 bytes   1024 bytes   8192
bytes
md5               5295.13k    18837.99k    56614.66k   113037.65k
157575.85k
des cbc          21280.46k    22224.36k    22536.87k    22626.65k
22686.38k
                  sign    verify    sign/s verify/s
rsa 1024 bits 0.007653s 0.000381s    130.7   2626.1

OpenSSL 0.9.8d 28 Sep 2006
built on: Wed May 30 00:55:23 PDT 2007
options:bn(64,32) md2(int) rc4(idx,int) des(ptr,risc1,16,long) aes(partial)
idea(int) blowfish(idx)
compiler:
gcc -DOPENSSL_THREADS -D_REENTRANT -DDSO_DLFCN -DHAVE_DLFCN_H -mcpu=pentium 
-DL_ENDIAN -DTERMIO -O3 -fomit-frame-pointer -Wall -DOPENSSL_BN_ASM_PART_WOR
DS -DOPENSSL_IA32_SSE2 -DSHA1_ASM -DMD5_ASM -DRMD160_ASM -DAES_ASM
available timing options: TIMES TIMEB HZ=100 [sysconf value]
timing function used: times
The 'numbers' are in 1000s of bytes per second processed.
type             16 bytes     64 bytes    256 bytes   1024 bytes   8192
bytes
md5               5355.29k    18880.64k    56515.93k   113145.51k
157908.99k
des cbc          21361.71k    22185.28k    22494.72k    22654.29k
22659.07k
                  sign    verify    sign/s verify/s
rsa 1024 bits 0.007612s 0.000380s    131.4   2629.5

	DS