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From lars hofhansl <la...@apache.org>
Subject Re: HBase read perfomnance and HBase client
Date Thu, 01 Aug 2013 04:33:46 GMT
Would be interesting to profile MultiGet. With RTT of 0.1ms, the internal RS friction is probably
the main contributor.
In fact MultiGet just loops over the set at the RS and calls single gets on the various regions.

Each Get needs to reseek into the block (even when it is cached, since KVs have variable size).

There are HBASE-6136 and HBASE-8362.


-- Lars

________________________________
From: Vladimir Rodionov <vladrodionov@gmail.com>
To: dev@hbase.apache.org; lars hofhansl <larsh@apache.org> 
Sent: Wednesday, July 31, 2013 7:27 PM
Subject: Re: HBase read perfomnance and HBase client


Some final numbers :

Test config:

HBase 0.94.6
blockcache=true, block size = 64K, KV size = 62 bytes (raw).

5 Clients: 96GB, 16(32) CPUs (2.2Ghz), CentOS 5.7
1 RS Server: the same config.

Local network with ping between hosts: 0.1 ms


1. HBase client hits the wall at ~ 50K per sec regardless of # of CPU,
threads, IO pool size and other settings.
2. HBase server was able to sustain 170K per sec (with 64K block size). All
from block cache. KV size = 62 bytes (very small). This is for single Get
op, 60 threads per client, 5 clients (on different hosts)
3. Multi - get hits the wall at the same 170K-200K per sec. Batch size
tested: 30, 100. The same performance absolutely as with batch size = 1.
Multi get has some internal issues on RegionServer side. May be excessive
locking or some thing else.





On Tue, Jul 30, 2013 at 2:01 PM, Vladimir Rodionov
<vladrodionov@gmail.com>wrote:

> 1. SCR are enabled
> 2. Single Configuration for all table did not work well, but I will try it
> again
> 3. With Nagel I had 0.8ms avg, w/o - 0.4ms - I see the difference
>
>
> On Tue, Jul 30, 2013 at 1:50 PM, lars hofhansl <larsh@apache.org> wrote:
>
>> With Nagle's you'd see something around 40ms. You are not saying 0.8ms
>> RTT is bad, right? Are you seeing ~40ms latencies?
>>
>> This thread has gotten confusing.
>>
>> I would try these:
>> * one Configuration for all tables. Or even use a single
>> HConnection/Threadpool and use the HTable(byte[], HConnection,
>> ExecutorService) constructor
>> * disable Nagle's: set both ipc.server.tcpnodelay and
>> hbase.ipc.client.tcpnodelay to true in hbase-site.xml (both client *and*
>> server)
>> * increase hbase.client.ipc.pool.size in client's hbase-site.xml
>> * enable short circuit reads (details depend on exact version of Hadoop).
>> Google will help :)
>>
>> -- Lars
>>
>>
>> ----- Original Message -----
>> From: Vladimir Rodionov <vladrodionov@gmail.com>
>> To: dev@hbase.apache.org
>> Cc:
>> Sent: Tuesday, July 30, 2013 1:30 PM
>> Subject: Re: HBase read perfomnance and HBase client
>>
>> This hbase.ipc.client.tcpnodelay (default - false) explains poor single
>> thread performance and high latency ( 0.8ms in local network)?
>>
>>
>> On Tue, Jul 30, 2013 at 1:22 PM, Vladimir Rodionov
>> <vladrodionov@gmail.com>wrote:
>>
>> > One more observation: One Configuration instance per HTable gives 50%
>> > boost as compared to single Configuration object for all HTable's - from
>> > 20K to 30K
>> >
>> >
>> > On Tue, Jul 30, 2013 at 1:17 PM, Vladimir Rodionov <
>> vladrodionov@gmail.com
>> > > wrote:
>> >
>> >> This thread dump has been taken when client was sending 60 requests in
>> >> parallel (at least, in theory). There are 50 server handler threads.
>> >>
>> >>
>> >> On Tue, Jul 30, 2013 at 1:15 PM, Vladimir Rodionov <
>> >> vladrodionov@gmail.com> wrote:
>> >>
>> >>> Sure, here it is:
>> >>>
>> >>> http://pastebin.com/8TjyrKRT
>> >>>
>> >>> epoll is not only to read/write HDFS but to connect/listen to clients
>> as
>> >>> well?
>> >>>
>> >>>
>> >>> On Tue, Jul 30, 2013 at 12:31 PM, Jean-Daniel Cryans <
>> >>> jdcryans@apache.org> wrote:
>> >>>
>> >>>> Can you show us what the thread dump looks like when the threads
are
>> >>>> BLOCKED? There aren't that many locks on the read path when reading
>> >>>> out of the block cache, and epoll would only happen if you need
to
>> hit
>> >>>> HDFS, which you're saying is not happening.
>> >>>>
>> >>>> J-D
>> >>>>
>> >>>> On Tue, Jul 30, 2013 at 12:16 PM, Vladimir Rodionov
>> >>>> <vladrodionov@gmail.com> wrote:
>> >>>> > I am hitting data in a block cache, of course. The data set
is very
>> >>>> small
>> >>>> > to fit comfortably into block cache and all request are directed
to
>> >>>> the
>> >>>> > same Region to guarantee single RS testing.
>> >>>> >
>> >>>> > To Ted:
>> >>>> >
>> >>>> > Yes, its CDH 4.3 . What the difference between 94.10 and 94.6
with
>> >>>> respect
>> >>>> > to read performance?
>> >>>> >
>> >>>> >
>> >>>> > On Tue, Jul 30, 2013 at 12:06 PM, Jean-Daniel Cryans <
>> >>>> jdcryans@apache.org>wrote:
>> >>>> >
>> >>>> >> That's a tough one.
>> >>>> >>
>> >>>> >> One thing that comes to mind is socket reuse. It used to
come up
>> more
>> >>>> >> more often but this is an issue that people hit when doing
loads
>> of
>> >>>> >> random reads. Try enabling tcp_tw_recycle but I'm not guaranteeing
>> >>>> >> anything :)
>> >>>> >>
>> >>>> >> Also if you _just_ want to saturate something, be it CPU
or
>> network,
>> >>>> >> wouldn't it be better to hit data only in the block cache?
This
>> way
>> >>>> it
>> >>>> >> has the lowest overhead?
>> >>>> >>
>> >>>> >> Last thing I wanted to mention is that yes, the client
doesn't
>> scale
>> >>>> >> very well. I would suggest you give the asynchbase client
a run.
>> >>>> >>
>> >>>> >> J-D
>> >>>> >>
>> >>>> >> On Tue, Jul 30, 2013 at 11:23 AM, Vladimir Rodionov
>> >>>> >> <vrodionov@carrieriq.com> wrote:
>> >>>> >> > I have been doing quite extensive testing of different
read
>> >>>> scenarios:
>> >>>> >> >
>> >>>> >> > 1. blockcache disabled/enabled
>> >>>> >> > 2. data is local/remote (no good hdfs locality)
>> >>>> >> >
>> >>>> >> > and it turned out that that I can not saturate 1 RS
using one
>> >>>> >> (comparable in CPU power and RAM) client host:
>> >>>> >> >
>> >>>> >> >  I am running client app with 60 read threads active
(with
>> >>>> multi-get)
>> >>>> >> that is going to one particular RS and
>> >>>> >> > this RS's load is 100 -150% (out of 3200% available)
- it means
>> >>>> that
>> >>>> >> load is ~5%
>> >>>> >> >
>> >>>> >> > All threads in RS are either in BLOCKED (wait) or
in IN_NATIVE
>> >>>> states
>> >>>> >> (epoll)
>> >>>> >> >
>> >>>> >> > I attribute this  to the HBase client implementation
which seems
>> >>>> to be
>> >>>> >> not scalable (I am going dig into client later on today).
>> >>>> >> >
>> >>>> >> > Some numbers: The maximum what I could get from Single
get (60
>> >>>> threads):
>> >>>> >> 30K per sec. Multiget gives ~ 75K (60 threads)
>> >>>> >> >
>> >>>> >> > What are my options? I want to measure the limits
and I do not
>> >>>> want to
>> >>>> >> run Cluster of clients against just ONE Region Server?
>> >>>> >> >
>> >>>> >> > RS config: 96GB RAM, 16(32) CPU
>> >>>> >> > Client     : 48GB RAM   8 (16) CPU
>> >>>> >> >
>> >>>> >> > Best regards,
>> >>>> >> > Vladimir Rodionov
>> >>>> >> > Principal Platform Engineer
>> >>>> >> > Carrier IQ, www.carrieriq.com
>> >>>> >> > e-mail: vrodionov@carrieriq.com
>> >>>> >> >
>> >>>> >> >
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in this
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>> >>>
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>> >
>>
>>
>

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