Messages in this thread | | | Date | Wed, 25 Dec 2002 23:44:08 -0800 | From | Andrew Morton <> | Subject | Re: Poor performance with 2.5.52, load and process in D state |
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Paolo Ciarrocchi wrote: > > Hi Andrew/Rik/Con/all > > Andrew, I promised you to run a few tests > using osdb (www.osdb.org with 40M of data)against both > 2.4.19 and 2.5.52 booting the kernel with the > mem=XXM paramter. > > I also played with the /proc/sys/vm/swappiness > parameter, I've ran all the tests with the standard > swappiness value (60), with 80 and 100. > > 100 means the 2.4 behaviour, isn't it ?
Not really. swappiness=100 is strict LRU, treating pagecache and mapped-into-process-memory pages identically. Smaller values will make the kernel prefer to preserve mapped-into-process-memory.
> Looking at the results it seems that the "standard" > value is too low, probably 80 is the best one. > What do you think ?
I would agree with that.
> ... > > 2.4.19 all x 778.65 seconds (0:12:58.65) > 2.5.52 all 60 768.98 seconds (0:12:48.98) > 2.5.52 all 80 770.43 seconds (0:12:50.43) > 2.5.52 all 100 771.76 seconds (0:12:51.76)
Only 1% difference. On my 4xPIII with mem=128M, 2.4.20-pre2 took 1080.55 seconds and 2.5.52-mm3 took 991.03. That's 9% faster, and from the profile:
c010a858 system_call 192 4.3636 c011e518 current_kernel_time 201 3.3500 c012cdbc __generic_file_aio_read 214 0.4652 c012bba0 kallsyms_lookup 219 0.8295 c012ccec file_read_actor 230 1.1058 c0145abc fget 318 4.1842 c01d3ed4 radix_tree_lookup 384 3.8400 c0144be0 vfs_read 409 1.3279 c01315f4 check_poison_obj 695 7.8977 c012c964 do_generic_mapping_read 1007 1.1988 c01d7ae0 __copy_user_intel 34130 213.3125 c0108a58 poll_idle 299231 3562.2738
it appears that this benefit came from the special usercopy code. What sort of CPU are you using? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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