Re: No swap being used

["Paul Krizak" <paul krizak amd com>]

I'd think that *using* swap would be a significant source of slowdowns. 
 If everything is in memory, then you're in fantastic shape, as far as 
I know.  Most of our servers never touch the swap partition.  We're even 
considering running without swap or /tmp in a diskless configuration.

Swap is slow, and the RHEL kernel tries to keep as much stuff in RAM as 
possible before resorting to paging to disk.  I'd look elsewhere for 
your slowdowns.

Paul Krizak                         5900 E. Ben White Blvd. MS 625
Advanced Micro Devices              Austin, TX  78741
Linux/Unix Systems Engineering      Phone: (512) 602-8775
Microprocessor Solutions Sector


Jeff Macfarland 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
>
> `swapon -s`:
>
> Filename                        Type            Size    Used    Priority
> /dev/sda2                       partition       2096472 0       -1
> /dev/sda3                       partition       2096472 0       -2
> /dev/sda5                       partition       2096440 0       -3
> /dev/sda6                       partition       2096440 0       -4
> /dev/sda7                       partition       2096440 0       -5
> /dev/sda8                       partition       2096440 0       -6
>
> `dmesg`:
> ...
> Adding Swap: 2096472k swap-space (priority -1)
> Adding Swap: 2096472k swap-space (priority -2)
> Adding Swap: 2096440k swap-space (priority -3)
> Adding Swap: 2096440k swap-space (priority -4)
> Adding Swap: 2096440k swap-space (priority -5)
> Adding Swap: 2096440k swap-space (priority -6)
> ...
>
> `grep swap /etc/fstab`:
> /dev/sda2     swap     swap     defaults     0 0
> /dev/sda3     swap     swap     defaults     0 0
> /dev/sda5     swap     swap     defaults     0 0
> /dev/sda6     swap     swap     defaults     0 0
> /dev/sda7     swap     swap     defaults     0 0
> /dev/sda8     swap     swap     defaults     0 0
>
> Doing `mkswap /dev/sda2; swapon -s` has no effect.
>
> Is there some secret setting to enable swap?