Re: [f2fs-dev] f2fs: dirty memory increasing during gc_urgent

[Chao Yu <yuchao0@huawei.com>]

Hi Ju Hyung,

On 2019/8/14 22:15, Ju Hyung Park wrote:
> Hi.
> 
> I'm reporting some strangeness with gc_urgent.
> 
> When running gc_urgent, I can see that dirty memory written in
> /proc/meminfo continuously getting increased until GC cannot find any
> more segments to clean.
> 
> I thought FG_GC are flushed.
> 
> And after GC ends, if I do `sync` and run gc_urgent again, it easily
> runs thousands of times more.
> 
> Is this an expected behavior?

I doubt that before triggering urgent GC, system has dirty datas in memory, then
when you trigger `sync`, GCed data and dirty data were flushed to devices
together, if we write dirty data with out-place-update model, it may make fragment.

So we can try
- sync
- trigger urgent GC
- sync
- cat /sys/kernel/debug/f2fs/status to check 'Dirty' field, the value should
close to zero

Thanks,


> 
> I would much prefer gc_urgent cleaning everything up at first run,
> without having to sync at the end and running gc_urgent again.
> 
> Thanks.
> 
> 
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