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Re: writing processes are blocking in log_wait_common with data=ordered



David Mansfield wrote:
> 
> ...
> One interesting and unexpected result is that running inside a looped back
> filesystem 1gb in size increases performance 4-fold from running on the
> real filesystem!  That is, ext3-ordered looped on top of ext3-ordered is
> much faster than ext3-ordered!  This is on kernel 2.4.17-rc2-aa2, which is
> a bit old, so it could be meaningless....

Heh.  The loop driver tells lies: when it signals I/O
completion, your data is still floating about in memory,
unwritten.  So yup, it'll run quicker.

> P.S.  I created a benchmark of this phenomenon called blktest.c.

Great stuff, thanks.





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