linux-kernel - Re: [PATCH tip/core/rcu 3/4] md/bitmap: Fix list_entry

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Message-ID: <5602E821.800@gmail.com>
Date:	Wed, 23 Sep 2015 19:57:53 +0200
From:	Patrick Marlier <patrick.marlier@...il.com>
To:	paulmck@...ux.vnet.ibm.com
Cc:	Steven Rostedt <rostedt@...dmis.org>, NeilBrown <neilb@...e.de>,
	linux-kernel@...r.kernel.org, mingo@...nel.org,
	laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
	dhowells@...hat.com, edumazet@...gle.com, dvhart@...ux.intel.com,
	fweisbec@...il.com, oleg@...hat.com, bobby.prani@...il.com,
	wangyun@...ux.vnet.ibm.com
Subject: Re: [PATCH tip/core/rcu 3/4] md/bitmap: Fix list_entry_rcu usage


On 09/22/2015 10:50 PM, Paul E. McKenney wrote:
> On Sun, Sep 13, 2015 at 09:10:24AM -0700, Paul E. McKenney wrote:
>> On Sun, Sep 13, 2015 at 12:06:33PM +0200, Patrick Marlier wrote:
>
> [ . . . ]
>
>>> Paul,
>>>
>>> This sounds good to me. It should fix the performance issue (will
>>> check with my benchmark).
>>
>> Thank you, looking forward to seeing the results!
>
> Just following up -- how is the benchmarking going?

Note that in my module I am using the kernel version 3.16.0-31 (I ported 
your change).
Here the results of my benchmark that tests rculist in the case of read 
only.

# 1st column : The number of threads
# 2nd : ops/s the original version
# 3rd : ops/s your version with lockless_dereference
1 883923 1747554
2 1741441 3543062
3 2462360 5103647
4 3437273 7176608
6 5155803 9812348
8 6718111 13330050
10 8519227 17458294
12 9773632 20298897
14 11555198 23191424
16 11643264 25125712

I get same performance with my patch.
So indeed it fixes the performance problem I was seeing.

Thanks a lot!
--
Pat
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