Messages in this thread | | | Date | Tue, 15 Jan 2002 17:42:36 +0100 | From | Klaus Meyer <> | Subject | Re: highmem=system killer, 2.2.17=performance killer ? |
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Stephan von Krawczynski wrote: > > On Tue, 15 Jan 2002 04:13:49 +0100 > Klaus Meyer <k.meyer@m3its.de> wrote: > > > i've got serious problems using 2.4.x kernels using highmem support. > > It seems to me that i'm not the only one, but the difference to most > > other ones is, > > that i can't use highmem because the system performance is terrible > > slow. > > > > the testbed: > > 1) Asus CUR-DLS (Server Set LE III) with two 1Ghz Pentiums, 2GB of ram > > Interestingly I have about the same setup and use, only I transfer about 25 GB > a day via nfs to an Asus CUV4XD with 2 GB under 2.4.18-pre3 and do not > experience any problem so far. I haven't had any with 2.4.17, too. Cache is > pretty heavy used, but I experience no slowdown or other weird things. Can this > be somehow chipset related? Maybe something about the DGE cards? I am using TP > 100MBit tulip-based. >
I dont think that the network driver is the one who causes problems, because the throughput is very nice, if i limit the memory to 1GB by hand. if files are in the cache I'm even getting a throughput of nearly 60 MB/S (using udp) ! (but sorry, not with kernel 2.2.17 => network throuput decreases significantly) The whole system is running quite stable and pretty fast using only 1GB of mem. Probably somebody can explain the difference what will happen if i have a kernel with highmem support (4GB or 64GB) compiled in, but using only 1GB of physically 2GB? Is the kernel aware how to use highmem in this case ? it seems to be that only a small amount of highmem will be used in this case:
cat /proc/meminfo reads: HighTotal: 131072 kB HighFree: 115628 kB
As I just took a look on the output of cat /proc/meminfo i got the idea that i'll increase the pysical swap space. (136M before that means > highmem). astonishing (using Suse kernel 2.4.16): after an increase to 2GB swap and using 1,5GB of mem the system runs quit a longer time with a good performance, but starting the copy process leads also to a slow down of the machine. Finally i could see that kupdated is suffering.
----------------------------------------------------------------------------- 5:56pm up 2 min, 1 user, load average: 2.97, 1.02, 0.36 34 processes: 29 sleeping, 5 running, 0 zombie, 0 stopped CPU0 states: 2.5% user, 96.0% system, 0.0% nice, 1.0% idle CPU1 states: 11.4% user, 95.0% system, 0.0% nice, -6.-5% idle Mem: 1545456K av, 452480K used, 1092976K free, 0K shrd, 19708K buff Swap: 2097136K av, 0K used, 2097136K free 400732K cached PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME COMMAND 7 root 15 0 0 0 0 RW 81.2 0.0 0:44 kupdated ------------------------------------------------------------------------------
As kupdated finished his work, the system was quite usefull and came back to a much more better performance.
Using the avail. 2 GB of ram led to the same effect.
So whats the relation between physical swap space and highmem and physical memory (and the chipset) ?
testing this configuration with the offical kernel 2.4.17 falls back to the known slow down.
It seems to be Suse has applied some patches or back porting ?!?
regards, Klaus - 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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