Обсуждение: Re: [PATCHES] update i386 spinlock for hyperthreading

Hi Manfred,

I'm using unixware 7 but couldn't compile your source with native cc, I
had to compile it with gcc.

here are the results:

Script started on Sat Dec 27 17:50:49 2003
/tmp 17:50:50: ./a.out
MOVETEST called by non-superuser, running with normal priority.
zerotest:    -1073736628 ticks;
zerotest:         -4372 ticks;
zerotest:           -52 ticks;
rep nop:           508 ticks;
rep nop:            88 ticks;
rep nop:            60 ticks;
nop:           256 ticks;
nop:           224 ticks;
nop:            92 ticks;
nop:            64 ticks;
nop:            12 ticks;
nop:             8 ticks;
nop:             0 ticks;
nop:            -4 ticks;
rep nop:            56 ticks;
rep nop:            44 ticks;
rep nop:            40 ticks;
zerotest:            -4 ticks;
rep nop:            24 ticks;
zerotest:            -4 ticks;
nop:             0 ticks;
zerotest:            -4 ticks;
nop:            -8 ticks;
zerotest:            -8 ticks;
rep nop:            32 ticks;
nop:           -16 ticks;
zerotest:            -4 ticks;
zerotest:            -4 ticks;
rep nop:            24 ticks;
zerotest:            -4 ticks;
nop:           -12 ticks;
^?
/tmp 17:53:34: exit

script done on Sat Dec 27 17:53:38 2003

Regards
On Sat, 27 Dec 2003, Manfred Spraul wrote:

> Date: Sat, 27 Dec 2003 12:22:45 +0100
> From: Manfred Spraul <manfred@colorfullife.com>
> To: ohp@pyrenet.fr
> Subject: Re: [PATCHES] update i386 spinlock for hyperthreading
>
> Hi Olivier,
>
> I have attached rep_nop.cpp. It's a simple C program (unfortunately
> filled with linux specific gccisms) that benchmarks the time for a
> single rep;nop instruction, compared to a normal nop and nothing at all.
>
> Which OS do you use? I can try to build an app for FreeBSD, and it
> should be possible to compile it under Windows with cygwin as well.
>
> Under Linux:
> $ gcc -O2 -o rep_nop rep_nop.cpp
> $ ./rep_nop
>
> Just run in for a few seconds and send back the output. Please add the
> mailing list back into the cc list.
> --
>     Manfred
>

-- 
Olivier PRENANT                    Tel: +33-5-61-50-97-00 (Work)
6, Chemin d'Harraud Turrou           +33-5-61-50-97-01 (Fax)
31190 AUTERIVE                       +33-6-07-63-80-64 (GSM)
FRANCE                          Email: ohp@pyrenet.fr
------------------------------------------------------------------------------
Make your life a dream, make your dream a reality. (St Exupery)

ohp@pyrenet.fr wrote:

>Hi Manfred,
>
>I'm using unixware 7 but couldn't compile your source with native cc, I
>had to compile it with gcc.
>
>here are the results:
>  
>
Thanks. The test app compares the time needed for three different short 
loops: a loop with six empty function calls, a loop with six function 
calls and one nop in the middle, and a loop with a "rep;nop;" in the middle.

Result:
- nop needs 0 cycles - executed in parallel.
- rep;nop between 24 and 60 cycles - long enough that the pipeline is 
emptied.

I've searched around for further info regarding the recommended spinlock 
algorithm:
- The optimization manual (google for "Intel 248966") contains a section 
about pause instructions: The memory ordering violation is from the 
multiple simultaneous reads that are executed due to pipelining the busy 
loop.
- It references the Application Note AP-949 "Using Spin-Loops on Intel 
Pentium 4 Processor and Intel Xeon Processor" for further details. 
Unfortunately the app notes are stored on cedar.intel.com, and that 
server appears to be down :-(

--   Manfred

How do you connect to postgres if it is running on a different machine. I
am looking for a telnet command in place of postmaster -D data

In postgresql.conf the first entry should be something like 'tcpip'.
Set it to 'true'. That's the equivalent of the postmaster -D.

HTH,
-Tony



ogeer@cs.queensu.ca (Nailah Ogeer) wrote in message news:<Pine.SOL.4.33.0312271407030.3848-100000@innovate>...
> How do you connect to postgres if it is running on a different machine. I
> am looking for a telnet command in place of postmaster -D data
> 
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 2: you can get off all lists at once with the unregister command
>     (send "unregister YourEmailAddressHere" to majordomo@postgresql.org)

El Sáb 27 Dic 2003 16:08, Nailah Ogeer escribió:
> How do you connect to postgres if it is running on a different machine. I
> am looking for a telnet command in place of postmaster -D data

Depends on what you want to do.
One way arounf would be:

1) Edit the pg_hba.conf where the PG server is running so that you can
actually connect to the DB.
2) Run this:

$ psql -d database -h host -U user

where database, host and user are self explained. :-)

If what you want is something different please explain yourself.

--
select 'mmarques' || '@' || 'unl.edu.ar' AS email;
-----------------------------------------------------------------
Martín Marqués                  |        mmarques@unl.edu.ar
Programador, Administrador, DBA |       Centro de Telemática
                       Universidad Nacional
                            del Litoral
-----------------------------------------------------------------