Bristol Digest, Vol 637, Issue 5

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Today's Topics:

1. Re: What is with swap? (Andrew)
2. Re: What is with swap? (nick robinson)
3. Re: What is with swap? (Keith Edmunds)
4. Re: What is with swap? (Andrew)


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Message: 1
Date: Thu, 17 Mar 2016 13:28:33 +0000
From: Andrew <andrewsoltau@gmail.com>
To: Bristol and Bath Linux User Group <bristol@mailman.lug.org.uk>
Subject: Re: [bristol] What is with swap?
Message-ID: <56EAB101.2040400@1dtv.com>
Content-Type: text/plain; charset="windows-1252"; Format="flowed"

On 17/03/16 06:17, Colin M Strickland wrote:
> Swap isn't bad. Heavy page swapping is bad

Many thanks to everyone. Thanks Colin for good clear info. I flirted
with not having swap but as a precaution it always seemed warranted.

The system is 64 bit so accessing all the memory is no problem. It does
use more than 4gb, but always less than 6, hence I am puzzled.

Home is on the ssd on a second partition with of course / on the start
of the drive. So /tmp is on the ssd. Had not thought of putting that on
the hdd. Could this be useful?

A couple of outputs in case there is info here I am blind to:


# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point> <type> <options> <dump> <pass>
# / was on /dev/sda1 during installation
UUID=7ccb26df-9429-4a81-9b27-10b3a9f491d5 / ext4
errors=remount-ro 0 1
# /home was on /dev/sda5 during installation
UUID=dde11948-b584-4af4-a2cb-723f5eb1c8b9 /home ext4
defaults 0 2
# swap
UUID=f8721b19-f826-4f0f-9735-7e7e3e968bf0 none swap
sw 0 0
# mount second hdd for backup
UUID=d0854ced-43a9-444e-9a48-99748b79bb0c /mnt/hdd1 ext4
defaults 0 2
UUID=932640ca-b826-4b3d-9897-99b0b3521db8 /mnt/hdd2 ext4
defaults 0 2
UUID=74a46cee-eb8c-496a-8e65-b2fdc6db22fe /mnt/hdd3 ext4
defaults 0 2


output of ls -l /dev/disk/by-uuid

total 0
lrwxrwxrwx 1 root root 10 Mar 12 13:21
74a46cee-eb8c-496a-8e65-b2fdc6db22fe -> ../../sdb4
lrwxrwxrwx 1 root root 10 Mar 12 13:21
7ccb26df-9429-4a81-9b27-10b3a9f491d5 -> ../../sda1
lrwxrwxrwx 1 root root 10 Mar 12 13:21
932640ca-b826-4b3d-9897-99b0b3521db8 -> ../../sdb5
lrwxrwxrwx 1 root root 10 Mar 12 13:21
d0854ced-43a9-444e-9a48-99748b79bb0c -> ../../sdb1
lrwxrwxrwx 1 root root 10 Mar 12 13:21
dde11948-b584-4af4-a2cb-723f5eb1c8b9 -> ../../sda5
lrwxrwxrwx 1 root root 10 Mar 12 13:21
f8721b19-f826-4f0f-9735-7e7e3e968bf0 -> ../../sdb3

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Message: 2
Date: Thu, 17 Mar 2016 15:51:54 +0000
From: nick robinson <nick@njrobinson.net>
To: andrew@1dtv.com, Bristol and Bath Linux User Group
<bristol@mailman.lug.org.uk>
Subject: Re: [bristol] What is with swap?
Message-ID:
<CADo8qK7T4zaia7oiS-7pmvb8RBXKNCM-U6qtR78mE2t6cLcyHw@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Hi

a few questions
How many firefox windows do you have open before this becomes a problem?
Are we talking windows or tab?
what size is your swap?




On 17 March 2016 at 13:28, Andrew <andrewsoltau@gmail.com> wrote:

> On 17/03/16 06:17, Colin M Strickland wrote:
>
> Swap isn't bad. Heavy page swapping is bad
>
>
> Many thanks to everyone. Thanks Colin for good clear info. I flirted with
> not having swap but as a precaution it always seemed warranted.
>
> The system is 64 bit so accessing all the memory is no problem. It does
> use more than 4gb, but always less than 6, hence I am puzzled.
>
> Home is on the ssd on a second partition with of course / on the start of
> the drive. So /tmp is on the ssd. Had not thought of putting that on the
> hdd. Could this be useful?
>
> A couple of outputs in case there is info here I am blind to:
>
>
> # /etc/fstab: static file system information.
> #
> # Use 'blkid' to print the universally unique identifier for a
> # device; this may be used with UUID= as a more robust way to name devices
> # that works even if disks are added and removed. See fstab(5).
> #
> # <file system> <mount point> <type> <options> <dump> <pass>
> # / was on /dev/sda1 during installation
> UUID=7ccb26df-9429-4a81-9b27-10b3a9f491d5 / ext4
> errors=remount-ro 0 1
> # /home was on /dev/sda5 during installation
> UUID=dde11948-b584-4af4-a2cb-723f5eb1c8b9 /home ext4
> defaults 0 2
> # swap
> UUID=f8721b19-f826-4f0f-9735-7e7e3e968bf0 none swap
> sw 0 0
> # mount second hdd for backup
> UUID=d0854ced-43a9-444e-9a48-99748b79bb0c /mnt/hdd1 ext4
> defaults 0 2
> UUID=932640ca-b826-4b3d-9897-99b0b3521db8 /mnt/hdd2 ext4
> defaults 0 2
> UUID=74a46cee-eb8c-496a-8e65-b2fdc6db22fe /mnt/hdd3 ext4
> defaults 0 2
>
>
> output of ls -l /dev/disk/by-uuid
>
> total 0
> lrwxrwxrwx 1 root root 10 Mar 12 13:21
> 74a46cee-eb8c-496a-8e65-b2fdc6db22fe -> ../../sdb4
> lrwxrwxrwx 1 root root 10 Mar 12 13:21
> 7ccb26df-9429-4a81-9b27-10b3a9f491d5 -> ../../sda1
> lrwxrwxrwx 1 root root 10 Mar 12 13:21
> 932640ca-b826-4b3d-9897-99b0b3521db8 -> ../../sdb5
> lrwxrwxrwx 1 root root 10 Mar 12 13:21
> d0854ced-43a9-444e-9a48-99748b79bb0c -> ../../sdb1
> lrwxrwxrwx 1 root root 10 Mar 12 13:21
> dde11948-b584-4af4-a2cb-723f5eb1c8b9 -> ../../sda5
> lrwxrwxrwx 1 root root 10 Mar 12 13:21
> f8721b19-f826-4f0f-9735-7e7e3e968bf0 -> ../../sdb3
>
>
> _______________________________________________
> Bristol mailing list
> Bristol@mailman.lug.org.uk
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Message: 3
Date: Thu, 17 Mar 2016 22:17:44 +0000
From: Keith Edmunds <kae@midnighthax.com>
To: bristol@mailman.lug.org.uk
Subject: Re: [bristol] What is with swap?
Message-ID: <20160317221744.727bd2d9@ws.midnighthax.com>
Content-Type: text/plain; charset=US-ASCII

On Thu, 17 Mar 2016 13:28:33 +0000, andrewsoltau@gmail.com said:

> So /tmp is on the ssd. Had not thought of putting that on
> the hdd. Could this be useful?

Probably not.

Run 'vmstat 1' in a terminal window and, when the problem occurs, see if
you have numbers other than zero in the 'si' and 'so' columns (occasional
non-zero is fine). If you consistently have numbers > 0 in those columns,
you are actively swapping which may, in turn, explain the sluggishness. If
you don't, you don't have a swap problem.

Install 'atop' and run 'atop 5' in a terminal. After the first five
seconds, look for any line that is drawn in red while the problem occurs.
If you see one (or more), let us know what those lines are.
--
"Why does God hate me so much? Is it because I don't believe in him?" -
Sidney Morgenbesser




------------------------------

Message: 4
Date: Fri, 18 Mar 2016 08:52:46 +0000
From: Andrew <andrewsoltau@gmail.com>
To: Bristol and Bath Linux User Group <bristol@mailman.lug.org.uk>
Subject: Re: [bristol] What is with swap?
Message-ID: <56EBC1DE.6060301@1dtv.com>
Content-Type: text/plain; charset="windows-1252"; Format="flowed"

On 17/03/16 22:17, Keith Edmunds wrote:
> On Thu, 17 Mar 2016 13:28:33 +0000, andrewsoltau@gmail.com said:
>
>> So /tmp is on the ssd. Had not thought of putting that on
>> the hdd. Could this be useful?
> Probably not.
>
> Run 'vmstat 1' in a terminal window and, when the problem occurs, see if
> you have numbers other than zero in the 'si' and 'so' columns (occasional
> non-zero is fine). If you consistently have numbers > 0 in those columns,
> you are actively swapping which may, in turn, explain the sluggishness. If
> you don't, you don't have a swap problem.
Yup, other numbers come up when I have the problem.
>
> Install 'atop' and run 'atop 5' in a terminal. After the first five
> seconds, look for any line that is drawn in red while the problem occurs.
> If you see one (or more), let us know what those lines are.
Got one line:
PAG | scan 6015 | | stall 0 | | |
swin 0 | | swout 125

(not easy highlighting it and right clicking it in 5 sec. I must be
really getting old!)


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