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Eric Wheeler

On Wed, 28 Jun 2017, Coly Li wrote:

On 2017/6/27 下午8:04, tang.junhui@zte.com.cn wrote:

quoted

Hello Eric, Coly,

I use a 1400G SSD device a bcache cache device,
and attach with 10 back-end devices,
and run random small write IOs,
when gc works, It takes about 15 seconds,
and the up layer application IOs was suspended at this time,
How could we bear such a long time IO stopping?
Is there any way we can avoid this problem?

I am very anxious about this question, any comment would be valuable.

I encounter same situation too.
Hmm, I assume there are some locking issue here, to prevent application
to send request and insert keys in LSM tree, no matter in writeback or
writethrough mode. This is a lazy and fast response, I need to check the
code then provide an accurate reply :-)

Should it bypass the cache during GC if GC takes longer than X amount 
of time?  That might still need to wait if writing to invalidate since the 
btree needs updated to invalidate, so that may not be an option...

-Eric