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Memory released after running rsync

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  Memory released after running rsync gamo <gamo@telecable.es> - 2015-11-29 14:51 +0100
    Re: Memory released after running rsync William Unruh <unruh@invalid.ca> - 2015-11-29 20:12 +0000
      Re: Memory released after running rsync gamo <gamo@telecable.es> - 2015-11-29 21:56 +0100
        Re: Memory released after running rsync William Unruh <unruh@invalid.ca> - 2015-11-29 21:16 +0000
          Re: Memory released after running rsync gamo <gamo@telecable.es> - 2015-11-29 23:52 +0100
        Re: Memory released after running rsync Pascal Hambourg <boite-a-spam@plouf.fr.eu.org> - 2015-11-30 00:33 +0100
          Re: Memory released after running rsync gamo <gamo@telecable.es> - 2015-11-30 07:16 +0100
            Re: Memory released after running rsync Teemu Likonen <tlikonen@iki.fi> - 2015-12-01 18:04 +0200
              Re: Memory released after running rsync gamo <gamo@telecable.es> - 2015-12-01 23:49 +0100
    Re: Memory released after running rsync Keith Keller <kkeller-usenet@wombat.san-francisco.ca.us> - 2015-11-29 18:36 -0800

#16390 — Memory released after running rsync

Hello,

I have a desktop machine with 32 GB RAM, and as expected most of
the memory is used as a cache. Sometimes I have few memory free,
less than 1 GB, and happens that after running 'rsync' the memory
reported by 'free' as free is increased notably. So the question
is: what kind of magic do the rsync program?

Thanks. Regards.

-- 
http://gamo.eu.pn/
The generation of random numbers is too important to be left to chance
Actually, 360 degree hater.

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#16395

On 2015-11-29, gamo <gamo@telecable.es> wrote:
>
> Hello,
>
> I have a desktop machine with 32 GB RAM, and as expected most of
> the memory is used as a cache. Sometimes I have few memory free,
> less than 1 GB, and happens that after running 'rsync' the memory
> reported by 'free' as free is increased notably. So the question
> is: what kind of magic do the rsync program?

memory which is unused is used by Linux as program chache. Instead of
releasing the program memory, the program is kept in memory in case it
is reused. HOwever, if some other program requires the memory, it is
released. Thus probably rsync uses that memory, and then releases it
before shutting down. Thus the memory is now free. It is no longer used
for program cache because that use was supreceeded by rsync, and no
longer used by rsync either. 

The above is just a guess. 
>
> Thanks. Regards.
>

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#16397

El 29/11/15 a las 21:12, William Unruh escribió:
> On 2015-11-29, gamo <gamo@telecable.es> wrote:
>>
>> Hello,
>>
>> I have a desktop machine with 32 GB RAM, and as expected most of
>> the memory is used as a cache. Sometimes I have few memory free,
>> less than 1 GB, and happens that after running 'rsync' the memory
>> reported by 'free' as free is increased notably. So the question
>> is: what kind of magic do the rsync program?
>
> memory which is unused is used by Linux as program chache. Instead of
> releasing the program memory, the program is kept in memory in case it
> is reused. HOwever, if some other program requires the memory, it is
> released. Thus probably rsync uses that memory, and then releases it
> before shutting down. Thus the memory is now free. It is no longer used
> for program cache because that use was supreceeded by rsync, and no
> longer used by rsync either.
>
> The above is just a guess.
>>
>> Thanks. Regards.
>>

I realized a test. One script to fill in the memory and get killed by 
the kernel or perl.

First it takes a while. Then, the computer seems hanged. I pressed ^C 
and after a moment, the program exit and I have only 5 GB of memory 
occupied.

So, I is a bit scary, but a 'releasemem' utility is factible.

-- 
http://gamo.eu.pn/
The generation of random numbers is too important to be left to chance
Actually, 360 degree hater.

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#16398

On 2015-11-29, gamo <gamo@telecable.es> wrote:
> El 29/11/15 a las 21:12, William Unruh escribi?:
>> On 2015-11-29, gamo <gamo@telecable.es> wrote:
>>>
>>> Hello,
>>>
>>> I have a desktop machine with 32 GB RAM, and as expected most of
>>> the memory is used as a cache. Sometimes I have few memory free,
>>> less than 1 GB, and happens that after running 'rsync' the memory
>>> reported by 'free' as free is increased notably. So the question
>>> is: what kind of magic do the rsync program?
>>
>> memory which is unused is used by Linux as program chache. Instead of
>> releasing the program memory, the program is kept in memory in case it
>> is reused. HOwever, if some other program requires the memory, it is
>> released. Thus probably rsync uses that memory, and then releases it
>> before shutting down. Thus the memory is now free. It is no longer used
>> for program cache because that use was supreceeded by rsync, and no
>> longer used by rsync either.
>>
>> The above is just a guess.
>>>
>>> Thanks. Regards.
>>>
>
> I realized a test. One script to fill in the memory and get killed by 
> the kernel or perl.
>
> First it takes a while. Then, the computer seems hanged. I pressed ^C 
> and after a moment, the program exit and I have only 5 GB of memory 
> occupied.
>
> So, I is a bit scary, but a 'releasemem' utility is factible.

factible? 

Anyway, in storing the programs, AFAIK the data is usually not stored as
well. And a script would not work that way. It is a very small program.
Try loading ooffice, xmaple, gimp, .... That should slowly fill up your
memory as those programs ( not data) are stored for potential later use.
(That is why the second time you open libreoffice is often so much
faster than the first-- unless you have SATAIII and an SDDrive. 
Look at the free memory. Then use your script to fill up the memory, and
see what happens when you close it. 
Note that the sysstem probably started swapping which would make it seem
really really slow. 

But why do you care? The programs are cached only if that space is not
needed. Why do you want empty memory sitting there doing nothing?


>

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#16399

El 29/11/15 a las 22:16, William Unruh escribió:
> But why do you care? The programs are cached only if that space is not
> needed. Why do you want empty memory sitting there doing nothing?

You are right. It's a mania to see how many memory free I have.

-- 
http://gamo.eu.pn/
The generation of random numbers is too important to be left to chance
Actually, 360 degree hater.

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#16401

gamo a écrit :
> 
> So, I is a bit scary, but a 'releasemem' utility is factible.

And useless. /proc/sys/vm/drop_cache is already available.

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#16408

El 30/11/15 a las 00:33, Pascal Hambourg escribió:
> gamo a écrit :
>>
>> So, I is a bit scary, but a 'releasemem' utility is factible.
>
> And useless. /proc/sys/vm/drop_cache is already available.
>

Ok, the 'file' is 'drop_caches' in my version.
Thanks.

-- 
http://gamo.eu.pn/
The generation of random numbers is too important to be left to chance
Actually, 360 degree hater.

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#16422

[Multipart message — attachments visible in raw view] — view raw

gamo@telecable.es [2015-11-30 07:16:25+01] wrote:

> El 30/11/15 a las 00:33, Pascal Hambourg escribió:
>> And useless. /proc/sys/vm/drop_cache is already available.
>
> Ok, the 'file' is 'drop_caches' in my version.

To release cached memory (as root):

	sync; echo 3 >/proc/sys/vm/drop_caches

See: https://www.kernel.org/doc/Documentation/sysctl/vm.txt

-- 
/// Teemu Likonen   - .-..   <https://github.com/tlikonen> //
// PGP: 4E10 55DC 84E9 DFF6 13D7 8557 719D 69D3 2453 9450 ///

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#16426

El 01/12/15 a las 17:04, Teemu Likonen escribió:
> gamo@telecable.es [2015-11-30 07:16:25+01] wrote:
>
>> El 30/11/15 a las 00:33, Pascal Hambourg escribió:
>>> And useless. /proc/sys/vm/drop_cache is already available.
>>
>> Ok, the 'file' is 'drop_caches' in my version.
>
> To release cached memory (as root):
>
> 	sync; echo 3 >/proc/sys/vm/drop_caches
>
> See: https://www.kernel.org/doc/Documentation/sysctl/vm.txt
>

Thanks, that doccumentation is very clear in not recommend
that usage for performance reasons.

-- 
http://gamo.eu.pn/
The generation of random numbers is too important to be left to chance
Actually, 360 degree hater.

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#16407

On 2015-11-29, gamo <gamo@telecable.es> wrote:
>
> I have a desktop machine with 32 GB RAM, and as expected most of
> the memory is used as a cache. Sometimes I have few memory free,
> less than 1 GB, and happens that after running 'rsync' the memory
> reported by 'free' as free is increased notably. So the question
> is: what kind of magic do the rsync program?

The kernel keeps files needed by rsync in cache.  It's nothing to worry
about.  Make sure you're looking at the second line in the free output
("-/+ buffers/cache"), which reports the memory actually available for
programs to use.

--keith

-- 
kkeller-usenet@wombat.san-francisco.ca.us
(try just my userid to email me)
AOLSFAQ=http://www.therockgarden.ca/aolsfaq.txt
see X- headers for PGP signature information

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