Re: [patches] Possible PowerPC LIBC optimization

[Mark Hatle <mark.hatle@xxxxxxxxxxxxx>]

Nitin Gupta wrote:
> Hello Mark/Conn,
> 
> Could you please send pointer to glibc thread about discussion of this
> patch?

The only glibc thread was one in which Conn asked about a prefetch macro
in glibc on April 24th (glibc alpha mailing list)..  He gave up after
that.  :|

--Mark

> Regards,
> Nitin
> -----Original Message-----
> From: Mark Hatle [mailto:mark.hatle@xxxxxxxxxxxxx] 
> Sent: Tuesday, May 15, 2007 10:02 AM
> To: patches@xxxxxxxxxx
> Cc: Conn Clark
> Subject: [patches] Possible PowerPC LIBC optimization
> 
> In the PowerPC community Conn Clark has been doing some interesting
> optimization work in glibc.  Much of it however, doesn't seem to be
> acceptable to the mainline glibc due to being very processor and
> architecture specific.
> 
> The following information describes a simple change that made a large
> performance improvement on the PPC 750 processor, and is believed will
> make similar improvements on other PowerPC that contain the dcbt
> instruction.
> 
> From Conn Clark:
>> To see where I made the changes just search for "dcbt". The first two
>> dcbt's in the functions _int_malloc and _int_free are the ones that
>> make the biggest difference. The rest seem to help but they fall
>> withing the noise margin of my test(a compile of glibc ).
> 
> Attached is the patch that Clark sent me against glibc-2.5.  I don't
> think it is directly applicable as stated to glibc, however the idea
> behind it appears to be sound.
> 
> There are point in the malloc/free that preloading the cache (at least
> on PPC) makes sense.  So adding hooks in these locations may allow us to
> configure in processor specific items that could dramatically improve
> the performance on various processors.
> 
> --Mark
>