Re: [f2fs-dev] write performance difference 3.18.21/git f2fs

[Jaegeuk K. <ja...@ke...>]

On Sat, Sep 26, 2015 at 03:59:57PM +0200, Marc Lehmann wrote:
> On Sat, Sep 26, 2015 at 12:52:53AM -0700, Jaegeuk Kim <ja...@ke...> wrote:
> > > Just for fun I'll start doing a -s64 run.
> 
> (which had the same result).
> 
> > Okay, so before finding bad commits, if possible, can you get block traces?
> 
> If you can teach me how to, sure!
> 
> In the meantime, maybe what happened is that f2fs leaves some gaps (e.g.
> for alignment) when writing now, and didn't in 3.18? That would somehow
> explain what I see.
> 
> Except that with the 3.18 code, there is virtually no read access while
> writing to the disk for hours. With f2fs git, there is a small 16kb read
> every half a minute or so, and after a while, a lot of "reading a few
> mb/s, while writing a few mb/s".

In order to verify this also, could you retrieve the following logs?

# echo 1 > /sys/kernel/debug/tracing/tracing_on
# echo 1 > /sys/kernel/debug/tracing/events/f2fs/f2fs_submit_read_bio/enable
# echo 1 > /sys/kernel/debug/tracing/events/f2fs/f2fs_submit_write_bio/enable
# cat /sys/kernel/debug/tracing/trace_pipe

Thanks,

> 
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