Re: write performance difference 3.18.21/4.2.1

[Marc Lehmann <schmorp@schmorp.de>]

On Thu, Sep 24, 2015 at 11:28:36AM -0700, Jaegeuk Kim <jaegeuk@kernel.org> wrote:
> > The log starts after only 20GB had been written. Here is the status output
> > at 25GB:
> > 
> > http://ue.tst.eu/734f7883107ee4dabff77602db92310b.txt
> 
> It seems about 700MB were moved by background GC.

And to quantify "slower", copying 2.1TiB took 18h, at 35.6MB/s. "sync" was
routinely taking minutes to execute.

As a sidenote, a "du" on cold cache pulled in data from the drive at
~26MB/s, which is quite impressive. At the number of files, that means
it is pulling in ~4.4kb/stat. It also means it stat's at 5869 files/s,
which is very good! I hadn't expected this from a flash file system on
rotational media.

> > Any idea why 4.2.1 performs so much worse than 3.8.21?
> 
> One thing that we can try is to run the latest f2fs source in v3.18.
> This branch supports f2fs for v3.18.

Will do!

> And, if possible, could you share the status output of both of v3.18 and v4.2?

Will do, this is the output for 4.2.1, after copying and having it sit
idle for a few hours.

http://ue.tst.eu/90522477a480ae7a3b71647269b31ff7.txt

-- 
                The choice of a       Deliantra, the free code+content MORPG
      -----==-     _GNU_              http://www.deliantra.net
      ----==-- _       generation
      ---==---(_)__  __ ____  __      Marc Lehmann
      --==---/ / _ \/ // /\ \/ /      schmorp@schmorp.de
      -=====/_/_//_/\_,_/ /_/\_\

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