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Description of problem: The random write workload generator (ffsb here) would get blocked for more than 120 seconds on xfs Version-Release number of selected component (if applicable): kernel-2.6.32-122.el6.x86_64 How reproducible: About 10% or so Steps to Reproduce: 1. Prepare a partition with 100+G free space 2. Run ffsb to generate random write workload(see attachment for ffsb config file) 3. Check dmesg for call trace Actual results: INFO: task ffsb:19705 blocked for more than 120 seconds. I attached the full log, and the sysrq-w output Expected results: No blocked messages Additional info: Here is a beaker job https://beaker.engineering.redhat.com/jobs/66287 http://beaker-archive.app.eng.bos.redhat.com/beaker-logs/2011/03/662/66287/135727/1476926/5890296///console_dmesg--kernel-filesystems-general-stress-ffsb-random_writes_threads_192.ffsb.log
Created attachment 488332 [details] full blocked call trace
Created attachment 488333 [details] sysrq-w output
Created attachment 488334 [details] ffsb config file Modify the 'location' string, then run: ffsb random_writes_threads_192.ffsb This requires ffsb-6.0-rc2
So 192 threads doing random buffered writes all at the same time to 1024 files? Sounds to me like you filled memory wih dirty pages and then discovered that writeback of random IO is really, really slow and that causes new writes to block for a long, long time. This doesn't look like a bug to me, just a case of overloading the IO subsystem by buffering tens of thousands of dirty pages and then wondering why everything grinds to a halt as we can only clean a few hundred pages/s.... Cheers, Dave.
(In reply to comment #5) > So 192 threads doing random buffered writes all at the same time to 1024 files? > Sounds to me like you filled memory wih dirty pages and then discovered that > writeback of random IO is really, really slow and that causes new writes to > block for a long, long time. This doesn't look like a bug to me, just a case of > overloading the IO subsystem by buffering tens of thousands of dirty pages and > then wondering why everything grinds to a halt as we can only clean a few > hundred pages/s.... > > Cheers, > > Dave. Thanks for clarifying, I'm just not sure if it's a bug or not. Close it as NOTABUG