[rhelv6-beta-list] My first experiences with RHEL6 beta

[John Summerfield]

James Findley wrote:
> On 06/15/2010 03:00 AM, John Summerfield wrote:
>> Jonathan Billings wrote:
>>> On Tue, Jun 15, 2010 at 08:22:27AM +0800, John Summerfield wrote:
>>>> Jonathan S Billings wrote:
>>>>> Swap improves performance on a system, due to the way the Linux memory
>>>>> manager works. Swap partitions are faster than swap files, and less
>>>>> likely to be lost, corrupted or removed by accident.
>>>> The performance claim has not been true for some time, I think as far
>>>> back as 2.4.
>>>
>>> The performance of a swap file vs. a swap partition is similar, I
>>> admit I was unaware of that. However, the performance of the linux
>>> memory manager IS improved by having available swap.
>>
>> in these cases?
>> 09:22 [summer at penguin tmp]$ swapon -s
>> 09:47 [summer at penguin tmp]$ ssh ns swapon -s
>> bash: swapon: command not found
>> 09:47 [summer at penguin tmp]$ root ns swapon -s
>> Filename Type Size Used Priority
>> /var/swapfile file 524280 1448 -1
>> Connection to ns closed.
>> 09:47 [summer at penguin tmp]$ root 192.168.4.253 swapon -s
>> Connection to 192.168.4.253 closed.
>> 09:47 [summer at penguin tmp]$ root mail.office.lan swapon -s
>> function siteBlock { echo $1 | tee -a /etc/squid/block.txt; }
>> function siteKill { echo $1 | tee -a /etc/squid/kill; }
>> Filename Type Size Used Priority
>> /var/swapfile file 524280 6140 4
>> /var/swapfile1 file 1048568 0 1
>> Connection to mail.office.lan closed.
>> 09:48 [summer at penguin tmp]$
> 
> Oh no! rsync doesn't really care if you have a swap file or not in your 
> arbitrary, naive test.  That doesn't mean anything.
> Certain dirty memory structures can be more effectively flushed if they 
> can be swapped out first.  This will use a few KB of swap, and only 
> generate a negligible amount of disk IO.

The swap files are so large because the space actually was required.


-- 

Cheers
John

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