On 2/26/2013 4:14 AM, Corinna Vinschen wrote:
On Feb 26 15:35, MITSUNARI Shigeo wrote:
Hi.
I found that the performance of malloc/free is wrong under multi-threading.
The following test program reproduces the problem.
The program repeats malloc and free under multi-thread.
I measured the timing on Cygwin and Linux.
timing(sec)| threadNum
-----------+----------+-------------
| 1 | 2
-----------+----------+-------------
Linux | 1.45 | 0.69
-----------+----------+-------------
Cygwin | 2.059 | 53.165
-----------+----------+-------------
The timing under Linux seems good scale but it is very wrong under Cygwin.
Is it intentional behavior or do I use pthread in bad way?
No, you're right. This is easily reproducable. I just had a look and
it seems that our malloc is really slow in multi-threading scenarios.
We're using Doug Lea's malloc unchanged with just additional locks
surrounding the underlying malloc/free calls.
This appears to be a serious performance problem. I just learned that
glibc uses another version of dlmalloc, called ptmalloc, which is a
derived version of dlmalloc optimized for multi-threading environments.
Perhaps we have to do the same, but I don't know how long it takes to
port ptmalloc to Cygwin and obviously I don't know how big the
performance gain might be.
Corinna
Does any host using newlib suffer from this problem, or is it exclusive
to Cygwin?
Chris
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