Messages in this thread | | | From | "Pedro M. Rodrigues" <> | Date | Fri, 30 Aug 2002 09:02:41 +0200 | Subject | PROBLEM: nfs & "Warning - running *really* short on DMA buffers" |
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Hello to all! While preparing to migrate some servers to Redhat 7.3 and doing some nfs tests before deployment i came across this "Warning - running *really* short on DMA buffers" error message repeated several times in dmesg and /var/log/messages. Something like this:
Aug 30 07:12:52 TEST kernel: Warning - running *really* short on DMA buffers Aug 30 07:12:52 TEST kernel: Warning - running *really* short on DMA buffers Aug 30 07:13:55 TEST last message repeated 18 times Aug 30 07:13:55 TEST kernel: DMA buffers Aug 30 07:13:55 TEST kernel: Warning - running *really* short on DMA buffers Aug 30 07:13:55 TEST last message repeated 320 times
Please note that the "kernel: DMA buffers" line was exactly what appeared. Sometimes ksyslog seems to eat characters when this happens. Anyway, the most intriguing part is that while i was testing with SGI Irix 6.5.13, Solaris 2.7 and Aix 4.3 nfs clients, only the SGI Irix ones make the problem appear, and only when testing async nfs v3 writes. In the same Irix machines, if i change the server nfs export to sync, or i mount the export forcing nfs v2, the problem doesn't repeat itself. The test i was making was a simple
time dd if=/dev/zero of=/vol01/nfstestrun01 bs=16k count=32768
Both the server and the clients have negotiated 100Mb FullDuplex, and for the curious of you that wonder if the results of the test are the same in all client machines, i have to say that at least for async writes, they are more or less the same. Please observe:
NFS v3 async writes(averages):
Irix 6.5.13 1:15.28 9.8% Aix 4.3 1:12.47 35.4% Solaris 2.7 1:13.66 15.6%
NFS v3 sync writes(averages):
Irix 6.5.13 2:14.10 5.2% Aix 4.3 1:29.46 25.3% (not a typo) Solaris 2.7 2:21.65 7.0%
I am attaching details on the server configuration, kernel, dmesg and vmstat output.
Thanks in advance,
Pedro Rodrigues The following section of this message contains a file attachment prepared for transmission using the Internet MIME message format. If you are using Pegasus Mail, or any another MIME-compliant system, you should be able to save it or view it from within your mailer. If you cannot, please ask your system administrator for assistance.
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