Re: [PATCH 10/15] readahead: add /debug/readahead/stats

[Rik van Riel]

On 02/23/2010 10:10 PM, Wu Fengguang wrote:
> Collect readahead stats when CONFIG_READAHEAD_STATS=y.
>
> This is enabled by default because the added overheads are trivial:
> two readahead_stats() calls per readahead.
>
> Example output:
> (taken from a fresh booted NFS-ROOT box with rsize=16k)
>
> $ cat /debug/readahead/stats
> pattern     readahead    eof_hit  cache_hit         io    sync_io    mmap_io       size async_size    io_size
> initial           524        216         26        498        498         18          7          4          4
> subsequent        181         80          1        130         13         60         25         25         24
> context            94         28          3         85         64          8          7          2          5
> thrash              0          0          0          0          0          0          0          0          0
> around            162        121         33        162        162        162         60          0         21
> fadvise             0          0          0          0          0          0          0          0          0
> random            137          0          0        137        137          0          1          0          1
> all              1098        445         63       1012        874          0         17          6          9
>
> The two most important columns are
> - io		number of readahead IO
> - io_size	average readahead IO size
>
> CC: Ingo Molnar<mingo@xxxxxxx>
> CC: Jens Axboe<jens.axboe@xxxxxxxxxx>
> CC: Peter Zijlstra<a.p.zijlstra@xxxxxxxxx>
> Signed-off-by: Wu Fengguang<fengguang.wu@xxxxxxxxx>

Acked-by: Rik van Riel <riel@xxxxxxxxxx>
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