Messages in this thread | | | Date | Thu, 26 Sep 2002 09:31:12 -0600 | From | "Justin T. Gibbs" <> | Subject | Re: Warning - running *really* short on DMA buffers while doing file transfers |
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> I reported this same problem some weeks ago - > http://marc.theaimsgroup.com/?l=linux-kernel&m=103069116227685&w=2 . > 2.4.20pre kernels solved the error messages flooding the console, and > improved things a bit, but system load still got very high and disk read > and write performance was lousy. Adding more memory and using a > completely different machine didn't help. What did? Changing the Adaptec > scsi driver to aic7xxx_old . The performance was up 50% for writes and > 90% for reads, and the system load was acceptable. And i didn't even had > to change the RedHat kernel (2.4.18-10) for a custom one. The storage was > two external Arena raid boxes, btw.
I would be interested in knowing if reducing the maximum tag depth for the driver improves things for you. There is a large difference in the defaults between the two drivers. It has only reacently come to my attention that the SCSI layer per-transaction overhead is so high that you can completely starve the kernel of resources if this setting is too high. For example, a 4GB system installing RedHat 7.3 could not even complete an install on a 20 drive system with the default of 253 commands. The latest version of the aic7xxx driver already sent to Marcelo drops the default to 32.
-- Justin
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