fc5 kernels after 1788 have excessive, kernel overhead

Dave Jones davej at redhat.com
Sat Dec 31 20:30:46 UTC 2005

On Sat, Dec 31, 2005 at 08:30:13PM +0000, Andy Burns wrote:
 > Anne & Lynn Wheeler wrote:
 > >long running application doing enet to disk transfer sustains
 > >2.6mbytes/sec transfer with 20% cpu busy (mostly non-kernel time).
 > Even that seems pretty low, I'd have thought you should be able to 
 > sustain 10-12MB/s
 > >post-1788 kernel, it is 100% cpu (mostly kernel time) and 600kbytes/sec
 > >sustained (an increase of over 20times in total cpu executed per byte
 > >transferred and possibly an increase of 100times in kernel cpu executed
 > >per byte transferred).
 > Just did a quick test here, a http wget of a 75MB file across a 100Mb/s 
 > full duplex link, where the file is fully cached on the source machine, 
 > I scrape 1.8MB/s and eat 75% CPU on a 3.0GHz HT P4, if I do some 
 > "intensive" monitoring with top, I can get it down to about 900KB/s
 > Of course we're not really proving anything here, we know that 
 > kernel1805 is built for debugging not for speed ...

my people page will have a new kernel with it turned off in about
an hour (buildsys permitting).


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