 | | | No swap being used | No swap being used 2006-01-12 - By Jeff Macfarland
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Collins, Kevin [MindWorks] wrote:
> 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 :)
Im fairly sure the source machine is usually a windows box with local
storage. Some of our users do use nfs however..Ill keep that in mind.
Thanks.
>
> 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.
>>
>
--
Jeff Macfarland (jmacfarland@(protected))
Nexa Technologies - 972.747.8879
Unix Administrator
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