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Re: Guile's I/O procedures should *not* do thread synchronization

From: Mark H Weaver
Subject: Re: Guile's I/O procedures should *not* do thread synchronization
Date: Sun, 06 Apr 2014 02:08:14 -0400
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux)

Andy Wingo <address@hidden> writes:

>>>> However, if we promise to do thread synchronization, we will condemn
>>>> Guile to forever having dog slow 'read-char', 'peek-char', 'write-char',
>>>> 'get-u8', 'peek-u8', and 'put-u8' operations.
>>> I think you are wrong about "dog slow".  Uncontended mutexes are fast,
>> I did some benchmarks of 'putchar' vs 'putchar_unlocked' in C, without
>> contention.  I think it's fair to assume that the GCC and GLIBC folks
>> did a reasonably good job of making both of these as fast as they could.
>> With gcc -O2, I tested two variants of this program: one with 'putchar'
>> and one with 'putchar_unlocked'.  On my YeeLoong (mips64el w/ N32 ABI),
>> the 'putchar_unlocked' version is faster by a factor of 26.3.
> On my i7-2620M, the difference is only a factor of 3.0.
> Now I think I understand your perspective; 26x is terrible.  But surely
> this is an architecture problem, and not a Guile problem?  The world
> will only get more multithreaded, and ignoring that does no one any
> service.

Now that I have access to the GCC Compile Farm, I repeated these
benchmarks on a variety of machines, and here are the results:

Ratio  CPU
26.3   Loongson 2F
14.0   PowerPC (Power7)
13.7   Loongson 3A
 9.33  ARMv6l
 6.47  UltraSparc IIe
 5.09  AMD Athlon II
 4.27  AMD Opteron
 3.46  Core 2 Duo P8600


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