Re: [PATCH] fix readahead breakage for sequential after randomreads

[Miklos Szeredi]

Ram Pai <linuxram@xxxxxxxxxx> wrote:
>
> Also I think the bug that Miklos, found is really hard to reproduce. Did
> he find this bug by code inspection? Its really really hard to get into
> a state where the current window is of size 1 page with zero pages in
> the readahead window, and then the sequential read pattern to just right
> then. 

I found it by accident. I did my testing with the following read
sequence:

page offset  num pages
7            1
0            1
35           1
23           1
42           1
33           1
29           1
100          200

I did not measure actual performance, but only looked at the length of
the page vector passed to my filesystem's readpages() method.

Miklos
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