Messages in this thread | | | From | Arun Dharankar <> | Subject | NFS/UDP/IP performance - 2.4.19 v/s 2.4.20, 2.4.20-pre3 | Date | Sat, 25 Jan 2003 01:05:27 -0500 |
| |
Greetings.
There seem to be a remarkable performance difference between 2.4.19 and 2.4.20/2.4.21-pre3 in regards to NFS writes/reads. I am not sure, but the problem may not in NFS but somewhere lower (UDP/IP or core).
For example, in my kernel and network configuration a write to a new file over NFS on 2.4.19 for 5MB takes 2.5 seconds or so. With everything same (including kernel configuration) 2.4.20 and 2.4.21-pre3 the same takes 11 or more seconds.
Also, when this file write is in progress, the system time goes up to 15% on 2.4.19, whereas on 2.4.20/21-pre3, it is about 4%. (I use sar/sysstat for this).
Memory accesses dont seem to be the issue either. Test program to check this show same times and are ok (as I expect on the board I use).
"netstat -s" or ifconfig or tcpdump traces dont seem to point to dropped messages, collisions, retransmissions etc.
The hardware configuration is PowerPC based, and there are no changes in the board specific IO subsystem between 2.4.19 and 2.4.20/21-pre3. The same compiler is used for building both the kernels, and have tried this even with GCC 3.2, with same results.
So, I dont suspect this is either board or compiler related issue.
Also, I see some differences in handling of the bottom halves in net/core/dev.c between 2.4.19 and 2.4.20/21-pre3. Although, I have not gone through these in details to assert that this is indeed the problem area.
Questions:
- Has anyone seen this? Perhaps on other platforms (x86 etc)? Is there some tunable that has been added (or is different) after 2.4.19, and which needs to be tuned?
- I have tried to enable kernel profiling to find any potential problem code areas. But given the low cpu utilization during these copies, I am not sure if this can give any useful info.
Could anyone offer any ideas to debug this?
I would appreciate if you copy me on any responses to this post, I dont subscribe to this list.
Best regards, -Arun. ADharankar@ATTBI.Com
- 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/
| |