Messages in this thread | | | Date | Tue, 27 Jul 1999 20:30:59 -0400 | From | Mark Lord <> | Subject | Re: (disk/cpu) kernel performance problem |
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Gerald Aigner wrote: ... > Yes, DMA is enabled. Please keep in mind that I am reading something like > 25-30 MB/second from the disks. > > I know that 45% (or in the case of 2.3.11 37%) is high and that's why > I ask. I really would like to have these cycles to do my calculations.
The 45% doesn't mean much by itself.
What does "hdparm -T" give you? (Uppercase T -- times memory/filesystem throughput, without accessing the device).
If it gives something like 60-70MB/sec, then your 25-30 is indeed 45% of your memory bandwidth.
Eg. My P2-400 with IDE drives gives 22MB/sec reading from the drives, chewing up 14-18% of the CPU, mostly in copying memory around. The -T thingie gives 116MB/sec, so we have:
22 / 116 = 18%
The darned thing even makes sense, given sufficient context. -- Mark Lord Real-Time Remedies Inc. mlord@pobox.com
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