[Bug libc/1541] Poor threaded application performance when using malloc

["sjmunroe at us dot ibm dot com" <sourceware-bugzilla at sourceware dot org>]

------- Additional Comments From sjmunroe at us dot ibm dot com  2005-10-25 15:53 -------
To run the testcase single threaded 
   ./malloc_test 128000 10000
   ...
   Average : 0.718383 seconds for 10000 requests of 128000 bytes, 491MB concurrent.

To run with 16 threads
   ./malloc_test 128000 10000 16
   ...
   Average : 1.280583 seconds for 10000 requests of 128000 bytes, 490MB concurrent.


These run quickly because 128000 is less than the cash threshold. Now try with a
malloc size larger than the MMAP_THRESHOLD:
   ./malloc_test 1280000 10000 16
   ... 
   Average : 227.594933 seconds for 10000 requests of 421006 bytes, 488MB
concurrent.

Notice the huge jump from 1.28 to 227 seconds while to total concurrent storage
remained constant around 490MB!

Now try a version of malloc-test that changes the MMAP_THRESHOLD to 16M:

   ./malloc-test_16M 1280000 10000 16
   ...
   Average : 7.473701 seconds for 10000 requests of 421006 bytes, 488MB concurrent.

The time comes down to a more reasonable 7.47 seconds. Finally to verify that
larger MMAP_THRESHOLD does not negatively impact smalled allocatoions try.

   ./malloc-test_16M 128000 10000 16
   ...
   1.066022 seconds for 10000 requests of 128000 bytes, 490MB concurrent.

Which in this case is faster than with to smalled default MMAP_THRESHOLD.

All runs on my dual 2GHz G5 (PPC64/970) system, but I see simular results on my
dual Athelon system. So I suspect this a common problem across SMP platforms.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=1541

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