Re: severe librbd performance degradation in Giant

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giant results with 6 osd
------------------------
bw=118129KB/s, iops=29532  : rbd_cache = false
bw=101771KB/s, iops=25442 : rbd_cache = true



fio config (note that numjobs is important, i'm going from 18000iops -> 29000 iops for numjobs 1->4)
----------
[global]
#logging
#write_iops_log=write_iops_log
#write_bw_log=write_bw_log
#write_lat_log=write_lat_log
ioengine=rbd
clientname=admin
pool=test
rbdname=test
invalidate=0    # mandatory
#rw=read
#rw=randwrite
#rw=write
rw=randread
bs=4K
direct=1
numjobs=4
group_reporting=1
size=10G

[rbd_iodepth32]
iodepth=32



ceph.conf
---------
       debug lockdep = 0/0
        debug context = 0/0
        debug crush = 0/0
        debug buffer = 0/0
        debug timer = 0/0
        debug journaler = 0/0
        debug osd = 0/0
        debug optracker = 0/0
        debug objclass = 0/0
        debug filestore = 0/0
        debug journal = 0/0
        debug ms = 0/0
        debug monc = 0/0
        debug tp = 0/0
        debug auth = 0/0
        debug finisher = 0/0
        debug heartbeatmap = 0/0
        debug perfcounter = 0/0
        debug asok = 0/0
        debug throttle = 0/0

        osd_op_num_threads_per_shard = 2
        osd_op_num_shards = 25
        filestore_fd_cache_size = 64
        filestore_fd_cache_shards = 32

         ms_nocrc = true
         cephx sign messages = false
         cephx require signatures = false

         ms_dispatch_throttle_bytes = 0
         throttler_perf_counter = false

[osd]
         osd_client_message_size_cap = 0
         osd_client_message_cap = 0
         osd_enable_op_tracker = false


----- Mail original ----- 

De: "Alexandre DERUMIER" <aderumier@xxxxxxxxx> 
À: "Somnath Roy" <Somnath.Roy@xxxxxxxxxxx> 
Cc: "Sage Weil" <sweil@xxxxxxxxxx>, "Josh Durgin" <josh.durgin@xxxxxxxxxxx>, ceph-devel@xxxxxxxxxxxxxxx, "Haomai Wang" <haomaiwang@xxxxxxxxx> 
Envoyé: Vendredi 19 Septembre 2014 13:30:24 
Objet: Re: severe librbd performance degradation in Giant 

>> with rbd_cache=true , I got around 60000iops (and I don't see any network traffic) 
>> 
>>So maybe they are a bug in fio ? 
>>maybe this is related to: 

Oh, sorry, this was my fault, I didn't fill the rbd with datas before doing the bench 

Now the results are (for 1 osd) 

firefly 
------ 
bw=37460KB/s, iops=9364 

giant 
----- 
bw=32741KB/s, iops=8185 


So, a little regression 

(the results are equals rbd_cache=true|false) 


I'll try to compare with more osds 

----- Mail original ----- 

De: "Alexandre DERUMIER" <aderumier@xxxxxxxxx> 
À: "Somnath Roy" <Somnath.Roy@xxxxxxxxxxx> 
Cc: "Sage Weil" <sweil@xxxxxxxxxx>, "Josh Durgin" <josh.durgin@xxxxxxxxxxx>, ceph-devel@xxxxxxxxxxxxxxx, "Haomai Wang" <haomaiwang@xxxxxxxxx> 
Envoyé: Vendredi 19 Septembre 2014 12:09:41 
Objet: Re: severe librbd performance degradation in Giant 

>>What tool are you using ? I used fio rbd. 

fio rbd too 


[global] 
ioengine=rbd 
clientname=admin 
pool=test 
rbdname=test 
invalidate=0 
#rw=read 
#rw=randwrite 
#rw=write 
rw=randread 
bs=4k 
direct=1 
numjobs=2 
group_reporting=1 
size=10G 

[rbd_iodepth32] 
iodepth=32 



I just notice something strange 

with rbd_cache=true , I got around 60000iops (and I don't see any network traffic) 

So maybe they are a bug in fio ? 
maybe this is related to: 


http://tracker.ceph.com/issues/9391 
"fio rbd driver rewrites same blocks" 

----- Mail original ----- 

De: "Somnath Roy" <Somnath.Roy@xxxxxxxxxxx> 
À: "Alexandre DERUMIER" <aderumier@xxxxxxxxx>, "Haomai Wang" <haomaiwang@xxxxxxxxx> 
Cc: "Sage Weil" <sweil@xxxxxxxxxx>, "Josh Durgin" <josh.durgin@xxxxxxxxxxx>, ceph-devel@xxxxxxxxxxxxxxx 
Envoyé: Jeudi 18 Septembre 2014 20:02:49 
Objet: RE: severe librbd performance degradation in Giant 

Alexandre, 
What tool are you using ? I used fio rbd. 

Also, I hope you have Giant package installed in the client side as well and rbd_cache =true is set on the client conf file. 
FYI, firefly librbd + librados and Giant cluster will work seamlessly and I had to make sure fio rbd is really loading giant librbd (if you have multiple copies around , which was in my case) for reproducing it. 

Thanks & Regards 
Somnath 

-----Original Message----- 
From: Alexandre DERUMIER [mailto:aderumier@xxxxxxxxx] 
Sent: Thursday, September 18, 2014 2:49 AM 
To: Haomai Wang 
Cc: Sage Weil; Josh Durgin; ceph-devel@xxxxxxxxxxxxxxx; Somnath Roy 
Subject: Re: severe librbd performance degradation in Giant 

>>According http://tracker.ceph.com/issues/9513, do you mean that rbd 
>>cache will make 10x performance degradation for random read? 

Hi, on my side, I don't see any degradation performance on read (seq or rand) with or without. 

firefly : around 12000iops (with or without rbd_cache) giant : around 12000iops (with or without rbd_cache) 

(and I can reach around 20000-30000 iops on giant with disabling optracker). 


rbd_cache only improve write performance for me (4k block ) 



----- Mail original ----- 

De: "Haomai Wang" <haomaiwang@xxxxxxxxx> 
À: "Somnath Roy" <Somnath.Roy@xxxxxxxxxxx> 
Cc: "Sage Weil" <sweil@xxxxxxxxxx>, "Josh Durgin" <josh.durgin@xxxxxxxxxxx>, ceph-devel@xxxxxxxxxxxxxxx 
Envoyé: Jeudi 18 Septembre 2014 04:27:56 
Objet: Re: severe librbd performance degradation in Giant 

According http://tracker.ceph.com/issues/9513, do you mean that rbd cache will make 10x performance degradation for random read? 

On Thu, Sep 18, 2014 at 7:44 AM, Somnath Roy <Somnath.Roy@xxxxxxxxxxx> wrote: 
> Josh/Sage, 
> I should mention that even after turning off rbd cache I am getting ~20% degradation over Firefly. 
> 
> Thanks & Regards 
> Somnath 
> 
> -----Original Message----- 
> From: Somnath Roy 
> Sent: Wednesday, September 17, 2014 2:44 PM 
> To: Sage Weil 
> Cc: Josh Durgin; ceph-devel@xxxxxxxxxxxxxxx 
> Subject: RE: severe librbd performance degradation in Giant 
> 
> Created a tracker for this. 
> 
> http://tracker.ceph.com/issues/9513 
> 
> Thanks & Regards 
> Somnath 
> 
> -----Original Message----- 
> From: ceph-devel-owner@xxxxxxxxxxxxxxx 
> [mailto:ceph-devel-owner@xxxxxxxxxxxxxxx] On Behalf Of Somnath Roy 
> Sent: Wednesday, September 17, 2014 2:39 PM 
> To: Sage Weil 
> Cc: Josh Durgin; ceph-devel@xxxxxxxxxxxxxxx 
> Subject: RE: severe librbd performance degradation in Giant 
> 
> Sage, 
> It's a 4K random read. 
> 
> Thanks & Regards 
> Somnath 
> 
> -----Original Message----- 
> From: Sage Weil [mailto:sweil@xxxxxxxxxx] 
> Sent: Wednesday, September 17, 2014 2:36 PM 
> To: Somnath Roy 
> Cc: Josh Durgin; ceph-devel@xxxxxxxxxxxxxxx 
> Subject: RE: severe librbd performance degradation in Giant 
> 
> What was the io pattern? Sequential or random? For random a slowdown makes sense (tho maybe not 10x!) but not for sequentail.... 
> 
> s 
> 
> On Wed, 17 Sep 2014, Somnath Roy wrote: 
> 
>> I set the following in the client side /etc/ceph/ceph.conf where I am running fio rbd. 
>> 
>> rbd_cache_writethrough_until_flush = false 
>> 
>> But, no difference. BTW, I am doing Random read, not write. Still this setting applies ? 
>> 
>> Next, I tried to tweak the rbd_cache setting to false and I *got back* the old performance. Now, it is similar to firefly throughput ! 
>> 
>> So, loks like rbd_cache=true was the culprit. 
>> 
>> Thanks Josh ! 
>> 
>> Regards 
>> Somnath 
>> 
>> -----Original Message----- 
>> From: Josh Durgin [mailto:josh.durgin@xxxxxxxxxxx] 
>> Sent: Wednesday, September 17, 2014 2:20 PM 
>> To: Somnath Roy; ceph-devel@xxxxxxxxxxxxxxx 
>> Subject: Re: severe librbd performance degradation in Giant 
>> 
>> On 09/17/2014 01:55 PM, Somnath Roy wrote: 
>> > Hi Sage, 
>> > We are experiencing severe librbd performance degradation in Giant over firefly release. Here is the experiment we did to isolate it as a librbd problem. 
>> > 
>> > 1. Single OSD is running latest Giant and client is running fio rbd on top of firefly based librbd/librados. For one client it is giving ~11-12K iops (4K RR). 
>> > 2. Single OSD is running Giant and client is running fio rbd on top of Giant based librbd/librados. For one client it is giving ~1.9K iops (4K RR). 
>> > 3. Single OSD is running latest Giant and client is running Giant based ceph_smaiobench on top of giant librados. For one client it is giving ~11-12K iops (4K RR). 
>> > 4. Giant RGW on top of Giant OSD is also scaling. 
>> > 
>> > 
>> > So, it is obvious from the above that recent librbd has issues. I will raise a tracker to track this. 
>> 
>> For giant the default cache settings changed to: 
>> 
>> rbd cache = true 
>> rbd cache writethrough until flush = true 
>> 
>> If fio isn't sending flushes as the test is running, the cache will stay in writethrough mode. Does the difference remain if you set rbd cache writethrough until flush = false ? 
>> 
>> Josh 
>> 
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-- 
Best Regards, 

Wheat 
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