Red Hat Bugzilla – Bug 76089
System stalls when writing to disk
Last modified: 2008-08-01 12:22:52 EDT
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Description of problem:
A 2cpu smp system exhibits poor scheduling performance when a process is
writing to disk via the ext3 file system. To drive the bug, create a process
that sequentially writes 3GB of data to a file on disk. Observe that 'cat
/proc/meminfo' takes minutes to return while the writes are taking place.
Observe that 'ssh' stalls for a long time when logging into the machine from a
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Create a process that sequentially writes to disk.
2. Run the process.
3. Try doing other work on the system.
Actual Results: 'cat /proc/meminfo' took minutes to return. 'ssh' took tens of
seconds to log into the system. (iostat reports a write throughput of about 10
to 11 MB/sec.)
Expected Results: Locking and scheduling algorithms should be tuned so that
long running processes that perform heavy I/O do not make the system unusable by
other processes which perform light I/O.
ext3 file system, dual cpu, 2GB of ram, no swap space.
Created attachment 80706 [details]
program to generate an I/O load
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