 | | | No swap being used | No swap being used 2006-01-12 - By Collins, Kevin [MindWorks]
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Since you see this with cvs checkout, it might be a filesystem issue.
Filesystem performance can be an issue when there are lots of small-ish
files, which is typical of large source-code repositories... Also, you
say the cvs repository is on software RAID, but what about the
filesystem its being check out to? That target fs is potentially getting
hit with a lot of small-block writes... and if its to a user's
NFS-mounted home directory, it really gets fun :)
Kevin
-- --Original Message-- --
From: taroon-list-bounces@(protected)
[mailto:taroon-list-bounces@(protected)] On Behalf Of William Warren
Sent: Thursday, January 12, 2006 10:04 AM
To: Discussion of Red Hat Enterprise Linux 3 (Taroon)
Subject: Re: No swap being used
It depends on kernel tuning but most times the kernel will start dumping
the file cache to free up ram. Once that is done it will start
swapping. You pretty much have to chew up all ram before swap stats
getting used. If you are having high iowaits then your issue is hdd or
IO not swapping. Check your RAID controller or you may just need to
upgrade to faster disks.
Jeff Macfarland wrote:
> Jussi Silvennoinen wrote:
>>> Sun V20z, RHEL 3u5, i386 kernel, 12GB RAM, 12GB swap
>>>
>>> This box hosts quite a few things, among them serving SunRay's.
We've
>>> been experiencing horrible slowdowns particularly during a cvs
checkout.
>>> Just noticed that NO swap is being used:
>>>
>>> output of `free`:
>>>
>>> total used free shared buffers
cached
>>> Mem: 12277844 12036764 241080 0 1333552
7502204
>>> -/+ buffers/cache: 3201008 9076836
>>> Swap: 12578704 0 12578704
>>
>> I guess yer a Solaris-admin? Things work a bit different in the
>> penguin-world.
>>
>> No need to swap = nothing gets swapped. Solaris does it a bit
different.
>> Over 7gb's of your ram is used for block cache so you're far away
from
>> actually needing to swap.
>>
>
> At what point will linux start using swap? Where there is absolutely
no
> free RAM left? Its been my understanding that swap will almost always
be
> used for idle processes regardless of amount of free ram left. I see
the
> output of free range from a few gigs free to 50M and at no point is
> anything swapped. I suppose I am just used to our old solaris boxes
though.
>
>> Instead, look at the output of 'top' when the slowdowns occur.
>
> We have. IO waits perecentage goes quite high and iostat shows 'await'
> time on the order of a few thousand ms for sda. The cvs repo is on a
> software raid partition though.
>
> Thanks for the swap info though.
>
--
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every tongue that shall rise against thee in judgment thou shalt
condemn. This is the heritage of the servants of the LORD, and their
righteousness is of me, saith the LORD.
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