Hello everyone,
After booting my linux box,I add a swap partition using "swapon /dev/hda5".but I found that swap partition was nerver used even 2M physics memory left.
why?
thanks
Bill
-
To unsubscribe from this list: send the line "unsubscribe linux-admin" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi, Bill:
Perhaps swap memory will not be used until
all physical memory has been consumed.
HTH, Chuck
"Bill J.Xu" wrote:
>
> Hello everyone,
>
> After booting my linux box,I add a swap partition using "swapon /dev/hda5".but I found that swap partition was nerver used even 2M physics memory left.
>
> why?
>
> thanks
>
> Bill
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
-
To unsubscribe from this list: send the line "unsubscribe linux-admin" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Try creating a program that consumes 90% or more of the physical memory.
chuck gelm net wrote:
> Hi, Bill:
>
> Perhaps swap memory will not be used until
> all physical memory has been consumed.
>
> HTH, Chuck
>
> "Bill J.Xu" wrote:
>
>>Hello everyone,
>>
>>After booting my linux box,I add a swap partition using "swapon /dev/hda5".but I found that swap partition was nerver used even 2M physics memory left.
>>
>>why?
>>
>>thanks
>>
>>Bill
>>-
>>To unsubscribe from this list: send the line "unsubscribe linux-admin" in
>>the body of a message to majordomo@vger.kernel.org
>>More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
-
To unsubscribe from this list: send the line "unsubscribe linux-admin" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
From a website I found:
http://www.netadmintools.com/art1.html
by Urbana Der Ga'had
Sometimes in the course of a system's existence you find that the swap
partition you set up at install-time just isn't enough anymore. Maybe y=
ou're
upgrading your system to RedHat 7.1 from a version of RedHat that used =
less
swap in relation to physical RAM. Perhaps you're running Oracle. Or may=
be
you're adding more memory and would like to increase swap space accordi=
ngly.
Our machine goblin is swapping like mad and we just can't take it down =
right
now to add more RAM. So to keep the machine from running out of memory
entirely and freezing, we'll add 128 MB more swap space by creating a s=
wap
file.
=46irst we check out the memory usage:
[root@goblin /root]# free -m
total used free shared buffers cach=
ed
Mem: 251 242 8 22 11 =
32
-/+ buffers/cache: 198 52
Swap: 133 133 0
Make sure we have 128 MB laying around somewhere:
[root@goblin /root]# df
=46ilesystem 1k-blocks Used Available Use% Mounted on
/dev/hda9 132207 33429 91952 27% /
/dev/hda1 15522 2537 12184 17% /boot
/dev/hda6 6143236 739000 5092176 13% /opt
/dev/hda7 1035660 836204 146848 85% /usr
/dev/hda5 2071384 344048 1622112 17% /usr/local
/dev/hda8 303344 14439 273244 5% /var
OK, we're going to make a swap file in /opt by using dd to create a fil=
e 128
MB in size.
[root@goblin /opt]# dd if=3D/dev/zero of=3Dswapfile bs=3D1024 count=3D1=
32207
132207+0 records in
132207+0 records out
[root@goblin /opt]# ls -l
total 132364
drwxr-xr-x 20 brenda users 4096 May 22 10:46 brenda
drwxr-xr-x 2 root root 16384 Feb 21 07:04 lost+found
-rw-r--r-- 1 root root 135379968 May 29 11:52 swapfile
Hey, I know, let's not make it world-readable...
[root@goblin /opt]# chmod 600 swapfile
[root@goblin /opt]# ls -l
total 132364
drwxr-xr-x 20 brenda users 4096 May 22 10:46 brenda
drwxr-xr-x 2 root root 16384 Feb 21 07:04 lost+found
-rw------- 1 root root 135379968 May 29 11:52 swapfile
Now we set up the swap area and enable it.
[root@goblin /opt]# mkswap swapfile
Setting up swapspace version 1, size =3D 135372800 bytes
[root@goblin /opt]# swapon swapfile
And viola! Twice as much swap as before.
[root@goblin /opt]# free
total used free shared buffers cached
Mem: 257632 254632 3000 2512 36172 150=
96
-/+ buffers/cache: 203364 54268
Swap: 268708 136512 132196
You can edit /etc/fstab to enable your swap file automatically at boot =
time.
By adding an entry like this:
/opt/swapfile swap swap defaults 0 0
Sure, swapping's ugly, slow and will grind your hard drives to dust. Bu=
t
even modern systems which have been tuned for performance require a gen=
erous
oodle of swap space.
Michael French
----- Original Message -----=20
=46rom: "Dar=EDo Mariani"
To:
Sent: Tuesday, November 25, 2003 1:41 PM
Subject: Re: a swap partition utilization question
> Try creating a program that consumes 90% or more of the physical memo=
ry.
>
> chuck gelm net wrote:
> > Hi, Bill:
> >
> > Perhaps swap memory will not be used until
> > all physical memory has been consumed.
> >
> > HTH, Chuck
> >
> > "Bill J.Xu" wrote:
> >
> >>Hello everyone,
> >>
> >>After booting my linux box,I add a swap partition using "swapon
/dev/hda5".but I found that swap partition was nerver used even 2M phys=
ics
memory left.
> >>
> >>why?
> >>
> >>thanks
> >>
> >>Bill
> >>-
> >>To unsubscribe from this list: send the line "unsubscribe linux-adm=
in"
in
> >>the body of a message to majordomo@vger.kernel.org
> >>More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
> >
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-adm=
in"
in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin=
" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
-
To unsubscribe from this list: send the line "unsubscribe linux-admin" =
in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Dear Chuck:
But I found that other linux box had used swap partition when many physical RAM left.
root@FW_knl:/home/shiy# free
total used free shared buffers cached
Mem: 255320 247564 7756 0 15652 197560
-/+ buffers/cache: 34352 220968
Swap: 996020 1484 994536
root@FW_knl:/home/shiy#
Bill
----- Original Message -----
From: "chuck gelm net"
To: "Bill J.Xu"
Cc:
Sent: Wednesday, November 26, 2003 4:51 AM
Subject: Re: a swap partition utilization question
> Hi, Bill:
>
> Perhaps swap memory will not be used until
> all physical memory has been consumed.
>
> HTH, Chuck
>
> "Bill J.Xu" wrote:
> >
> > Hello everyone,
> >
> > After booting my linux box,I add a swap partition using "swapon /dev/hda5".but I found that swap partition was nerver used even 2M physics memory left.
> >
> > why?
> >
> > thanks
> >
> > Bill
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-admin" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
-
To unsubscribe from this list: send the line "unsubscribe linux-admin" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Bill J.Xu wrote:
> > > After booting my linux box,I add a swap partition using "swapon
> > > /dev/hda5".but I found that swap partition was nerver used even
> > > 2M physics memory left.
> > >
> > > why?
> >
> > Perhaps swap memory will not be used until
> > all physical memory has been consumed.
>
> But I found that other linux box had used swap partition when many
> physical RAM left.
>
> root@FW_knl:/home/shiy# free
> total used free shared buffers cached
> Mem: 255320 247564 7756 0 15652 197560
> -/+ buffers/cache: 34352 220968
> Swap: 996020 1484 994536
> root@FW_knl:/home/shiy#
How long has the first box been up? And how intensive is memory demand
on that box?
Swap won't be used at all until physical memory becomes close to being
exhausted. However, after that point, even if more memory becomes
available, data won't be moved back into RAM unless it is actually
used.
There is often some data which will never be used again (e.g. memory
which is used by persistent daemons, but only during the
initialisation; the 6 getty processes running on tty1-tty6 which
typically never get used on a system which is running X, etc). Such
data is a strong candidate for being swapped out; once that happens,
it will typically never be swapped in again.
So, when a system is booted, there will always be a period when no
swap is used. If memory demand is low, that period may last
indefinitely. OTOH, once memory demand has been sufficiently high to
have required the use of swap, swap usage will probably never drop
back to zero.
--
Glynn Clements
-
To unsubscribe from this list: send the line "unsubscribe linux-admin" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi, Clements:
Thank you for your detailed explains first.
I use the linux box as a firewall, so it is highly loaded at any time.At most time, it's available physical RAM is less 2M, but SWAP partition is never used. This
make me confused.
Bill
----- Original Message -----
From: "Glynn Clements"
To: "Bill J.Xu"
Cc: "chuck gelm net"
Sent: Wednesday, November 26, 2003 8:32 PM
Subject: Re: a swap partition utilization question
>
> Bill J.Xu wrote:
>
> > > > After booting my linux box,I add a swap partition using "swapon
> > > > /dev/hda5".but I found that swap partition was nerver used even
> > > > 2M physics memory left.
> > > >
> > > > why?
> > >
> > > Perhaps swap memory will not be used until
> > > all physical memory has been consumed.
> >
> > But I found that other linux box had used swap partition when many
> > physical RAM left.
> >
> > root@FW_knl:/home/shiy# free
> > total used free shared buffers cached
> > Mem: 255320 247564 7756 0 15652 197560
> > -/+ buffers/cache: 34352 220968
> > Swap: 996020 1484 994536
> > root@FW_knl:/home/shiy#
>
> How long has the first box been up? And how intensive is memory demand
> on that box?
>
> Swap won't be used at all until physical memory becomes close to being
> exhausted. However, after that point, even if more memory becomes
> available, data won't be moved back into RAM unless it is actually
> used.
>
> There is often some data which will never be used again (e.g. memory
> which is used by persistent daemons, but only during the
> initialisation; the 6 getty processes running on tty1-tty6 which
> typically never get used on a system which is running X, etc). Such
> data is a strong candidate for being swapped out; once that happens,
> it will typically never be swapped in again.
>
> So, when a system is booted, there will always be a period when no
> swap is used. If memory demand is low, that period may last
> indefinitely. OTOH, once memory demand has been sufficiently high to
> have required the use of swap, swap usage will probably never drop
> back to zero.
>
> --
> Glynn Clements
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
-
To unsubscribe from this list: send the line "unsubscribe linux-admin" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
perl -e '$x=3D"x"x(.9*2*2**30)'
On Tue, 25 Nov 2003, Dar=EDo Mariani wrote:
> Date: Tue, 25 Nov 2003 18:41:11 -0300
> From: Dar=EDo Mariani
> To: linux-admin@vger.kernel.org
> Subject: Re: a swap partition utilization question
>=20
> Try creating a program that consumes 90% or more of the physical memo=
ry.
>=20
> chuck gelm net wrote:
> > Hi, Bill:
> >=20
> > Perhaps swap memory will not be used until
> > all physical memory has been consumed.
> >=20
> > HTH, Chuck
> >=20
> > "Bill J.Xu" wrote:
> >=20
> >>Hello everyone,
> >>
> >>After booting my linux box,I add a swap partition using "swapon /de=
v/hda5".but I found that swap partition was nerver used even 2M physics=
memory left.
> >>
> >>why?
> >>
> >>thanks
> >>
> >>Bill
> >>-
> >>To unsubscribe from this list: send the line "unsubscribe linux-adm=
in" in
> >>the body of a message to majordomo@vger.kernel.org
> >>More majordomo info at http://vger.kernel.org/majordomo-info.html
> >=20
> >=20
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-adm=
in" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> >=20
>=20
>=20
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin=
" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>=20
-
To unsubscribe from this list: send the line "unsubscribe linux-admin" =
in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html