linux-kernel - Re: LowFree pattern

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Message-ID: <4A9FC8CE.3070005@tmr.com>
Date:	Thu, 03 Sep 2009 09:46:54 -0400
From:	Bill Davidsen <davidsen@....com>
To:	Adayadil Thomas <adayadil.thomas@...il.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: LowFree pattern

Adayadil Thomas wrote:
>> What problem did you see that you traced to LowFree?
>>     
>
> I have set this device as a bridge. Higher latency and low throughput seem
> to be related to LowFree. There are also packet drops at the interface
> when LowFree is too low.
>
> I have another device which has 4G RAM split into 900M LowMem and
> the rest as HighMem. In that case also, LowMem goes to a low level, say 8M
> and although HighMem has ~2G free, the system gives OOPS (related to
> page_alloc failures)
> when acting as a bridge (passing packets).
>
>   
Then /proc/sys/vm tuning may help.
>
>
> On Wed, Sep 2, 2009 at 3:22 PM, Bill Davidsen<davidsen@....com> wrote:
>   
>> Adayadil Thomas wrote:
>>     
>>> Greetings.
>>>
>>> I am running a centos linux with 2.6.20 version kernel. The system has
>>> 1G of RAM.
>>>
>>> As time goes by the LowFree becomes really low. Right now it shows
>>> 137M .. but it goes as low as 8M or so
>>>
>>> The command -
>>> echo 3 > /proc/sys/vm/drop_caches
>>> brings back the LowFree to way up high.
>>>
>>> The question I have is whether the system by itself release the cache
>>> (drop cache) automatically
>>> to maintain a reasonable LowFree?
>>> Is this configurable?
>>>
>>>       
>> You can change the parameters in /rpoc/sys/vm if you wish, but what makes
>> you think this is needed? Cache is dropped as memory is needed, and
>> drop_cache in general is a good way to slow the system.
>>
>>     
>>> Any information or help is much appreciated.
>>>
>>>       
>> What problem did you see that you traced to LowFree?
>>
>>     
>>> cat /proc/meminfo
>>> MemTotal:      1034788 kB
>>> MemFree:        138240 kB
>>> Buffers:         99260 kB
>>> Cached:         177776 kB
>>> SwapCached:      51740 kB
>>> Active:         605172 kB
>>> Inactive:       113572 kB
>>> HighTotal:      130720 kB
>>> HighFree:          252 kB
>>> LowTotal:       904068 kB
>>> LowFree:        137988 kB
>>> SwapTotal:     1048568 kB
>>> SwapFree:       976332 kB
>>> Dirty:             380 kB
>>> Writeback:           0 kB
>>> AnonPages:      441348 kB
>>> Mapped:          15540 kB
>>> Slab:           146088 kB
>>> SReclaimable:   104288 kB
>>> SUnreclaim:      41800 kB
>>> PageTables:       1596 kB
>>> NFS_Unstable:        0 kB
>>> Bounce:              0 kB
>>> CommitLimit:   1565960 kB
>>> Committed_AS:   590576 kB
>>> VmallocTotal:   114680 kB
>>> VmallocUsed:     15052 kB
>>> VmallocChunk:    99348 kB
>>>       


-- 
bill davidsen <davidsen@....com>
  CTO TMR Associates, Inc

"Now we have another quarterback besides Kurt Warner telling us during postgame
interviews that he owes every great thing that happens to him on a football
field to his faith in Jesus. I knew there had to be a reason why the Almighty
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			-- Arthur Troyer on Tim Tebow (Sports Illustrated)

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