Messages in this thread | | | Date | Thu, 21 Jan 1999 11:20:54 +0100 (MEZ) | From | "Dr. Michael Weller" <> | Subject | Tar (but not cp) is incredible slow on certain dirs; request for comments/solution ideas/clues. |
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Hi people,
I've the following weird behaviour on a Compaq Proliant, 1Gig phys ram, Smart2 Compaq raid adapter with 6 disk Raid 5 array, 2 Xeon CPU's.
I tried using both CPU's or only one (disabling it from the bios). I tried kernel 2.0.36 and 2.2.0pre7 (always with SMP compiled in (even when only 1 CPU was used)). I also tried restricting the kernel memory to 64MB (side note: It appeared (!) to be a little faster with this setting, I assume handling/searching 1Gig of disk caches is much too slow. If it is not possible to speed the handling of cache memory up, maybe it is smarter to allow to set the kernel to use a maximum of n MB of buffer/caches memory.
Anyway, effect under all those kernels/# of CPU's is as follows: I try to backup / (whole linux is in one partition) to another disk, file on same disk, or even /dev/null (it doesn't matter). It runs nicely. But when it comes to /usr/src/linux-2.2.0pre7 where the 2.2.0pre7 sources are, it slows down to a crawl. That means it backs up one of these really tiny *.c and *.h files there per 1 or 2 seconds. Basically, it is impossible to back this dir up in any reasonable time.
I used tar -l as to exclude /proc and /mnt where the destination disk was mounted. Still, even 'tar -cvf/dev/null /usr/src' showed the exact same behaviour although it slowed down faster as it came faster to /usr/src/linux-2.2.0pre7 .
During the slow down, top claims system is well over 90% percent idle, CPU time consumed by tar and general system time spent is virtually zero (1 or 2 %). Tar is not locked in an uninterruptible sleep waiting for a device ('D') nor is there any apparent high disk activity (it just gets these tiny files every few seconds).
To make things even more weird, cp -rv /usr/src /mnt works like a greased weasel. So, a simple filesystem/disk cache/dname cache/disk device or driver issue can IMHO be excluded.
Now, honestly, this is the very first time with linux I really have no clue what's going on. Therefore any comments and ideas are appreciated.
Michael.
P.S. Files and disks are currently moved around a bit more on this machine. I'll see if the same holds when /usr/src/linux-2.2.0pre7 was moved to another partition.
--
Michael Weller: eowmob@exp-math.uni-essen.de, eowmob@ms.exp-math.uni-essen.de, or even mat42b@spi.power.uni-essen.de. If you encounter an eowmob account on any machine in the net, it's very likely it's me.
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