Jaydeep; since your primary key involves a clustering column, you may be
having pretty wide rows. The read would be sequential. The latency could be
acceptable, if the read were to involve really wide rows.
If your primary key was like ((a,b)) without the clustering column, it's
like reading a key value pair, and 40ms latency may have been a concern.
Bottom Line : The latency depends on how wide the row is.
On Tue, Sep 22, 2015 at 1:27 PM, sai krishnam raju potturi <
pskraj...@gmail.com> wrote:
> thanks for the information. Posting the query too would be of help.
>
> On Tue, Sep 22, 2015 at 11:56 AM, Jaydeep Chovatia <
> chovatia.jayd...@gmail.com> wrote:
>
>> Please find required details here:
>>
>> - Number of req/s
>>
>> 2k reads/s
>>
>> - Schema details
>>
>> create table test {
>>
>> a timeuuid,
>>
>> b bigint,
>>
>> c int,
>>
>> d int static,
>>
>> e int static,
>>
>> f int static,
>>
>> g int static,
>>
>> h int,
>>
>> i text,
>>
>> j text,
>>
>> k text,
>>
>> l text,
>>
>> m set<text>
>>
>> n bigint
>>
>> o bigint
>>
>> p bigint
>>
>> q bigint
>>
>> r int
>>
>> s text
>>
>> t bigint
>>
>> u text
>>
>> v text
>>
>> w text
>>
>> x bigint
>>
>> y bigint
>>
>> z bigint,
>>
>> primary key ((a, b), c)
>>
>> };
>>
>> - JVM settings about the heap
>>
>> Default settings
>>
>> - Execution time of the GC
>>
>> Avg. 400ms. I do not see long pauses of GC anywhere in the log file.
>>
>> On Tue, Sep 22, 2015 at 5:34 AM, Leleu Eric <eric.le...@worldline.com>
>> wrote:
>>
>>> Hi,
>>>
>>>
>>>
>>>
>>>
>>> Before speaking about tuning, can you provide some additional
>>> information ?
>>>
>>>
>>>
>>> - Number of req/s
>>>
>>> - Schema details
>>>
>>> - JVM settings about the heap
>>>
>>> - Execution time of the GC
>>>
>>>
>>>
>>> 43ms for a read latency may be acceptable according to the number of
>>> request per second.
>>>
>>>
>>>
>>>
>>>
>>> Eric
>>>
>>>
>>>
>>> *De :* Jaydeep Chovatia [mailto:chovatia.jayd...@gmail.com]
>>> *Envoyé :* mardi 22 septembre 2015 00:07
>>> *À :* user@cassandra.apache.org
>>> *Objet :* High read latency
>>>
>>>
>>>
>>> Hi,
>>>
>>>
>>>
>>> My application issues more read requests than write, I do see that under
>>> load cfstats for one of the table is quite high around 43ms
>>>
>>>
>>>
>>> Local read count: 114479357
>>>
>>> Local read latency: 43.442 ms
>>>
>>> Local write count: 22288868
>>>
>>> Local write latency: 0.609 ms
>>>
>>>
>>>
>>>
>>>
>>> Here is my node configuration:
>>>
>>> RF=3, Read/Write with QUORUM, 64GB RAM, 48 CPU core. I have only 5 GB of
>>> data on each node (and for experiment purpose I stored data in tmpfs)
>>>
>>>
>>>
>>> I've tried increasing concurrent_read count upto 512 but no help in read
>>> latency. CPU/Memory/IO looks fine on system.
>>>
>>>
>>>
>>> Any idea what should I tune?
>>>
>>>
>>>
>>> Jaydeep
>>>
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>>
>>
>
