Messages in this thread | | | Date | Tue, 08 Jul 2003 07:11:19 -0700 | From | "Martin J. Bligh" <> | Subject | [Bug 890] New: performance regression compared to 2.4.20 under tight RAM conditions |
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http://bugme.osdl.org/show_bug.cgi?id=890
Summary: performance regression compared to 2.4.20 under tight RAM conditions Kernel Version: 2.5.73 Status: NEW Severity: normal Owner: akpm@digeo.com Submitter: idan@idanso.dyndns.org
Distribution: debian unstable
Hardware Environment: Pentium III 700Mhz I815E Based motherboard 64MB SDRAM 133 WD 6GB harddrive, UDMA2
Software Environment: GCC 3.3-2 glibc 2.3.1-16 Swap partition 123MB Swap file(on ext3 fs) of about 96MB
Problem Description:
For quite a time I had the feeling that the 2.5.x kernels perform worse than 2.4.x on my box, especially when having to do aggrassive swapping(Switching between relatively heavyweight(ram wise) applications)
I considered this feeling subjective at first, however, eventually I took the time to write some benchmarking code and compare results.
The code(attached) is pretty trivial, it forks, mallocs and initialize a very large bulk of memory(I used total RAM*1.5), in order to force the system to swap, and simulate two processes fighting on RAM space when there is no enough of that scared resource:-)
After both processes end their work, the parent process reports on the total running time.
The code was compiled using gcc 3.3 with -O2 parameter.
I've done 20 iterations on each of the three kernels: Stock debian 2.4.20 (kernel-source-2.4.20-5) Stock vanilla 2.5.73 with preempt Stock vanilla 2.5.73 without preempt
Result are at follows: 2.4.20 : Mean - 14.1732 Max - 16.0875 Min - 12.9977 2.5.73 : Mean - 17.1692 Max - 21.8161 Min - 15.4827 2.5.73(w/o prempt): Mean - 16.9054 Max - 19.0174 Min - 15.4137
As can be seen, the differences are quite significant, about three seconds on average, which I believe may be related to the increased swapping time I have encountered.
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