Re: [RFC][PATCH] the proposal of improve page reclaim by throttle

[minchan Kim]

I miss CC's. so I resend.


First of all, I tried test it in embedded board.

---
<test machine>
      CPU:  200MHz(ARM926EJ-S)
      MEM:  32M
      SWAP: none
      KERNEL : 2.6.25-rc1

<test 1> - NO SWAP

before :

Running with 5*40 (== 200) tasks.

Time: 12.591
       Command being timed: "./hackbench.arm 5 process 100"
       User time (seconds): 0.78
       System time(seconds): 13.39
       Percent of CPU this job got: 99%
       Elapsed (wall clock) time (h:mm:ss or m:ss): 0m 14.22s
       Major (requiring I/O) page faults: 20
       max parallel reclaim tasks:     30
       max consumption time of
        try_to_free_pages():           789

after:

Running with 5*40 (== 200) tasks.
Time: 11.535
       Command being timed: "./hackbench.arm 5 process 100"
       User time (seconds): 0.69
       System time (seconds): 12.42
       Percent of CPU this job got: 99%
       Elapsed (wall clock) time (h:mm:ss or m:ss): 0m 13.16s
       Major (requiring I/O) page faults: 18
       max parallel reclaim tasks:     4
       max consumption time of
       try_to_free_pages():           740

<test 2> - SWAP
before:
Running with 6*40 (== 240) tasks.
Time: 121.686
       Command being timed: "./hackbench.arm 6 process 100"
       User time (seconds): 1.89
       System time (seconds): 44.95
       Percent of CPU this job got: 37%
       Elapsed (wall clock) time (h:mm:ss or m:ss): 2m 3.79s
       Major (requiring I/O) page faults: 230
       max parallel reclaim tasks:     56
       max consumption time of
       try_to_free_pages():           10811


after :
Running with 6*40 (== 240) tasks.
Time: 67.757
       Command being timed: "./hackbench.arm 6 process 100"
       User time (seconds): 1.56
       System time (seconds): 35.41
       Percent of CPU this job got: 52%
       Elapsed (wall clock) time (h:mm:ss or m:ss): 1m 9.87s
       Major (requiring I/O) page faults: 16
       max parallel reclaim tasks:     4
       max consumption time of
         try_to_free_pages():           6419

<test 3> NO_SWAP

before:

' OOM killer kill hackbench!!!'

after :
Time: 16.578
       Command being timed: "./hackbench.arm 6 process 100"
       User time (seconds): 0.71
       System time (seconds): 17.92
       Percent of CPU this job got: 99%
       Elapsed (wall clock) time (h:mm:ss or m:ss): 0m 18.69s
       Major (requiring I/O) page faults: 22
       max parallel reclaim tasks:     4
       max consumption time of
        try_to_free_pages():           1785

===============================

It was a very interesting result.
In embedded system, your patch improve performance a little in case
without noswap(normal case in embedded system).
But, more important thing is OOM occured when I made 240 process
without swap device and vanilla kernel.
Then, I applied your patch, it worked very well without OOM.

I think that's why zone's page_scanned was six times greater than
number of lru pages.
At result, OOM happened.

So, I think your patch also improves performance in embedded system.

In case OOM didn't occur, reclaiming performance without swap device
was better than one with swap device.
Now, I think we need to improve reclaiming procedure in embedded
system(UP and NO swap).

On Wed, Feb 20, 2008 at 7:09 PM, KOSAKI Motohiro
<kosaki.motohiro@xxxxxxxxxxxxxx> wrote:
> Hi
>
>
>  > > >  * max parallel reclaim tasks:
>  > > >  *  max consumption time of
>  > > >         try_to_free_pages():
>  > >
>  > > sorry, I inserted debug code to my patch at that time.
>  >
>  > Could you send me that debug code ?
>  > If you will send it to me, I will test it my environment (ARM-920T, Core2Duo).
>  > And I will report test result.
>
>  attached it.
>  but it is very messy ;-)
>
>  usage:
>  ./benchloop.sh
>
>  sample output
>  =========================================================
>  max reclaim 2
>  Running with 120*40 (== 4800) tasks.
>  Time: 34.177
>  14.17user 284.38system 1:43.85elapsed 287%CPU (0avgtext+0avgdata 0maxresident)k
>  0inputs+0outputs (3813major+148922minor)pagefaults 0swaps
>  max prepare time: 4599 0
>  max reclaim time: 2350 5781
>  total
>  8271
>  max reclaimer
>  4
>  max overkill
>  62131
>  max saved overkill
>  9740
>
>
>  max reclaimer represent to max parallel reclaim tasks.
>  total represetnto max consumption time of try_to_free_pages().
>
>  Thanks
>
>



-- 
Thanks,
barrios
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