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From Todd Lipcon <t...@cloudera.com>
Subject Re: How to flush `block_cache_capacity_mb` easily?
Date Mon, 10 Apr 2017 22:46:23 GMT
On Sun, Apr 9, 2017 at 6:38 PM, Jason Heo <jason.heo.sde@gmail.com> wrote:

> Hi Todd.
>
> I hope you had a good weekend.
>
> Exactly, I'm testing the latency of cold-cache reads from SATA disks and
> performance of difference schema designs as well.
>
> We currently using Elasticsearch for a analytic service. ES has a "clear
> cache API" feature, it makes me easy to test.
>
>
Makes sense. I don't think it would be particularly difficult to add such
an API. Any interest in contributing a patch? I'm happy to point you in the
right direction, if so.

-Todd


> 2017-04-08 5:05 GMT+09:00 Todd Lipcon <todd@cloudera.com>:
>
>> Hey Jason,
>>
>> Can I ask what the purposes of the testing is?
>>
>> One thing to note is that we're currently leaving a fair bit of
>> performance on the table for cold-cache reads from spinning disks. So, if
>> you find that the performance is not satisfactory, it's worth being aware
>> that we will likely make some significant improvements in this area in the
>> future.
>>
>> https://issues.apache.org/jira/browse/KUDU-1289 has some details.
>>
>> -Todd
>>
>> On Fri, Apr 7, 2017 at 8:44 AM, Dan Burkert <danburkert@apache.org>
>> wrote:
>>
>>> 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
>>>>
>>>
>>>
>>
>>
>> --
>> Todd Lipcon
>> Software Engineer, Cloudera
>>
>
>


-- 
Todd Lipcon
Software Engineer, Cloudera

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