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From Dan Burkert <danburk...@apache.org>
Subject Re: How to flush `block_cache_capacity_mb` easily?
Date Fri, 07 Apr 2017 15:44:17 GMT
Hi Jason,

There is no command to have Kudu evict its block cache, but restarting the
tablet server process will have that effect.  Ideally all written data will
be flushed before the restart, otherwise startup/bootstrap will take a bit
longer. Flushing typically happens within 60s of the last write.  Waiting
for flush and compaction is also a best-practice for read-only benchmarks.
I'm not sure if someone else on the list has an easier way of determining
when a flush happens, but I typically look at the 'MemRowSet' memory usage
for the tablet on the /mem-trackers HTTP endpoint; it should show something
minimal like 256B if it's fully flushed and empty.  You can also see
details about how much memory is in the block cache on that page, if that
interests you.

- Dan

On Thu, Apr 6, 2017 at 11:23 PM, Jason Heo <jason.heo.sde@gmail.com> wrote:

> Hi.
> I'm using Apache Kudu 1.2 on CDH 5.10.
> Currently, I'm doing a performance test of Kudu.
> Flushing OS Page Cache is easy, but I don't know how to flush
> `block_cache_capacity_mb` easily.
> I currently execute SELECT statement over a unnecessarily table to evict
> cached block of testing table.
> It is cumbersome, so I'd like to know is there a command for flushing
> block caches (or another kudu's caches which I don't know yet)
> Thanks.
> Regards,
> Jason

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