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Glibc change exposing bugsGlibc change exposing bugsPosted Nov 10, 2010 20:08 UTC (Wed) by jwb (guest, #15467)In reply to: Glibc change exposing bugs by dlang Parent article: Glibc change exposing bugs
Sure, but Linus doesn't even say what CPU he tested on. The commit message for the change to memcpy claims a 4x improvement on Core 2.
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Glibc change exposing bugs Posted Nov 10, 2010 21:03 UTC (Wed) by fuhchee (subscriber, #40059) [Link]
It would be nice if such patches were accompanied not but just statements of seen performance changes, but actual reproduction scripts, so one can test for oneself.
Glibc change exposing bugs Posted Nov 10, 2010 23:05 UTC (Wed) by patrick_g (subscriber, #44470) [Link] >>> Linus doesn't even say what CPU he tested onLinus use a Core i5 at home (see this post).
Glibc change exposing bugs Posted Nov 11, 2010 0:26 UTC (Thu) by jwb (guest, #15467) [Link]
Then it makes sense that he didn't see a speedup because the patch claims 1x speeds on Core i7. The improvement is seen on Atom and Core2.
Glibc change exposing bugs Posted Nov 11, 2010 5:01 UTC (Thu) by nicooo (guest, #69134) [Link]
This change is starting to sound more and more pointless.
Glibc change exposing bugs Posted Nov 11, 2010 6:54 UTC (Thu) by madscientist (subscriber, #16861) [Link]
Well, I have a core2 and I'd LOVE to get 4x speed improvement on memcpy(), which is probably the single most widely used function in all of C programming.
So it doesn't sound useless to me.
Glibc change exposing bugs Posted Nov 11, 2010 9:42 UTC (Thu) by dgm (subscriber, #49227) [Link]
Also, any improvement to Atom performance can only be welcome.
Glibc change exposing bugs Posted Nov 11, 2010 12:00 UTC (Thu) by alankila (subscriber, #47141) [Link]
I took a simple oprofile trace of me using my desktop for a while. Sad to say, but in that trace glibc's memcpy() used 0.24 % of time.
It would probably be better idea for majority of systems to just remove memcpy() and just replace it with memmove() which showed up with 0.17 %. Together, that would add up to 0.5 % at most, I suppose.
Glibc change exposing bugs Posted Nov 11, 2010 16:26 UTC (Thu) by jedbrown (subscriber, #49919) [Link]
Here's my benchmark on Core 2. The Core 2 implementation in glibc-2.12.1 is *forward* (not reverse like on Nehalem, I don't know which way it is on Atom), and the performance difference between glibc and Linus' implementation goes both ways.
http://www.reddit.com/r/programming/comments/e4bq0/glibc_...
Glibc change exposing bugs Posted Nov 11, 2010 0:57 UTC (Thu) by MattPerry (guest, #46341) [Link]
> Linus use a Core i5 at home (see this post).
But we don't know if he ran his test on that computer. There's not enough information to tie the two together. It would help if Linus stated what CPU he used to run the test on.
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