RE: [f2fs-dev] [PATCH] f2fs: refactor flush_nat_entries codes for reducing NAT writes

[Chao Yu]

Hi all,

There are problem in this patch, please ignore this patch, sorry for the noise.
I will resend later.

> -----Original Message-----
> From: Chao Yu [mailto:chao2.yu@xxxxxxxxxxx]
> Sent: Saturday, June 14, 2014 7:48 PM
> To: Jaegeuk Kim
> Cc: linux-fsdevel@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx
> Subject: [f2fs-dev] [PATCH] f2fs: refactor flush_nat_entries codes for reducing NAT writes
> 
> Although building NAT journal in cursum reduce the read/write work for NAT
> block, but previous design leave us lower performance when write checkpoint
> frequently for these cases:
> 1. if journal in cursum has already full, it's a bit of waste that we flush all
>    nat entries to page for persistence, but not to cache any entries.
> 2. if journal in cursum is not full, we fill nat entries to journal util
>    journal is full, then flush the left dirty entries to disk without merge
>    journaled entries, so these journaled entries may be flushed to disk at next
>    checkpoint but lost chance to flushed last time.
> 
> In this patch we merge dirty entries located in same NAT block to nat entry set,
> and linked all set to list, sorted ascending order by entries' count of set.
> Later we flush entries in sparse set into journal as many as we can, and then
> flush merged entries to disk.
> 


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