On 2021/8/27 23:22, Daeho Jeong wrote:
I'd like to add a fixed chunk/hole fragmentation mode in addition, then
userspace can control the fragmented chunk/hole with fixed size.
How do you think of renaming "fragment:block" to "fragment:rand_block", and
then I can add "fragment:fixed_block" option and its logic in addition?
The reason I added the randomness on these values is the segment
selection in SSR mode.
If all the segments have the same free block counts, f2fs will
allocate a new segment sequentially in SSR.
I'm fine with this, since test program can customize different fragment
degree on segments by setting different chunk/hole size.
This was what I didn't want. Plus, in the real world, the size of hole
and chunk will be different in different segments.
But, if you think we need this "fragment:fixed_block" mode, I am happy
to have it. :)
Thanks a lot. :)
As you said it needs to be aligned to real world fragmentation, I notice that:
with this way, we can't simulate similar fragment in FTL, due to its page
mapping architecture, all fragmented data/node in filesystem will be written
sequentially into its blocks.
In order to simulate fragment in FTL, we need to:
- write data (chunk size) with dummy pages (hole size) to devices
- issue discards on those holes
I guess fragmenting device (erase blocks) at the same time wouldn't be
original intention of this patch, right?
Thanks,
Do we need to consider multiple thread scenario? in such case,
.fragment_remained_chunk may update randomly.
In addition, multiple log headers share one .fragment_remained_chunk,
it may cause unexpected result, it means there may be continuous holes
or chunks in locality due to swithing between different log headers.
Thanks,
Oh, I overlooked that point. I am going to add the variable for each
segment as you said before.
Thanks,
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