Messages in this thread | | | Date | Fri, 10 Jun 2005 16:13:09 +0900 | From | Takashi Ikebe <> | Subject | Re: Real-time problem due to IO congestion. |
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I see. The program which I tested is just sample, and I wanted to know the phenomena is spec or bug. I also understand that this problem is spec, and need to apply some buffering to such applications.
Thank you.
Andrew Morton wrote: > Takashi Ikebe <ikebe.takashi@lab.ntt.co.jp> wrote: > >>There are 2 type processes in test environment. >> 1. The real-time needed process (run on with high static priority) >> The process wake up every 10ms, and wake up, write some log (the >> test case is current CPU clock via tsc) to the file. >> >> 2. The process which make IO load >> The process have large memory size, and kill the process with dumping. >> The process's memory area exceeds 70% of whole physical >> RAM.(Actually 1.5GB memory area while whole RAM is 2GB) >> >> Whenever during dumping, the real-time needed process sometimes stop for >> long time during write system call. (sometimes exceeds 1000ms) > > > The writeback code does attempt to give some preference to realtime tasks > (in get_dirty_limits()), but it can only work up to a point. > > Frankly, your application is poorly designed. If you want sub-10ms > responsiveness you shouldn't be doing disk I/O. The realtime task should > hand the data off to a non-realtime task for writeout, with suitable > amounts of buffering in between.
-- Takashi Ikebe - 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/
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