| Title: | DIGITAL UNIX (FORMERLY KNOWN AS DEC OSF/1) |
| Notice: | Welcome to the Digital UNIX Conference |
| Moderator: | SMURF::DENHAM |
| Created: | Thu Mar 16 1995 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 10068 |
| Total number of notes: | 35879 |
In one of our 8400 setup, we are experiencing an unusually high system activity while copying file from one disk to another. The target is on UFS on LSM on HSZ/RAID1. One of the CPU shows 100% system mode with marely 3MB I/O transfer rate. When we instrument with iprobe, we find a ubc routine 'ubc_page_alloc' consuming all the CPU time. How do we fix it? Our UBC min and max settings are minimum (1 and 2%), but with the similar setting in other systems the ubc_page_alloc does not consume any CPU cycles. We are using 4.0 rev 546. Thanks in advance. /KK/
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 9730.1 | NABETH::alan | Dr. File System's Home for Wayward Inodes. | Tue May 06 1997 19:26 | 9 | |
Would this file happen to be sparse? Since holes don't require any disk I/O to read, they are only constrained by the write speed. If the file is small enough and the writes can be absorbed by the cache, your copy is will run at CPU speed and likely saturate the CPU. Also, if you're reading the same file over and over and it happens to fit in the cache that will also tend to remove the disk as a bottle neck. | |||||
| 9730.2 | KITCHE::schott | Eric R. Schott USG Product Management | Tue May 06 1997 22:37 | 6 | |
I think your ubc settings have something to do with this...why would you set them to 1 and 2 %? put them back to a reasonable value before asking folks to investigate.. | |||||