Messages in this thread | | | Date | Sat, 13 Oct 2012 20:33:27 +0100 | From | Alex Bligh <> | Subject | Re: Local DoS through write heavy I/O on CFQ & Deadline |
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--On 13 October 2012 21:53:09 +0800 Hillf Danton <dhillf@gmail.com> wrote:
> Take a look at the "wait for writeback" problem please. > > Linux 3.0+ Disk performance problem - wrong pdflush behaviour > https://lkml.org/lkml/2012/10/10/412
I'm guessing that's related but may not be the whole story. My test case is rather simpler, and Viktor says that with the patch causing his regression reverted, "After I've set the dirty_bytes over the file size the writes are never blocked.". That suggests to me that in order to avoid write blocking he needs dirty_bytes larger than the file size. As the bytes written in my test case exceed RAM, that's going to be be an issue as dirty_bytes is always going to be hit; I think it Viktor's case he is trying to avoid it being hit at all.
Or perhaps I have the wrong end of the stick.
-- Alex Bligh
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