System swappiness setting warning - important enough to display when shell starts?

[David Medinets <da...@gmail.com>]

I don't know the impact when this setting is too high. Apparently the
default in Ubuntu is 60. I only noticed the warning because I was
looking at log files randomly. I'm wondering if this check is
important enough to be done when the shell starts and to display the
error to the console at that time.

This was the message:

[server.Accumulo] WARN : System swappiness setting is greater than ten
(60) which can cause time-sensitive operations to be delayed.
Accumulo is time sensitive b
ecause it needs to maintain distributed lock agreement.

Re: System swappiness setting warning - important enough to display when shell starts?

[Eric Newton <er...@gmail.com>]

That's true, but this is not for performance.  If you run a large VM on
linux, with swappiness at 60, the OS will steal your pages, cause you to
swap, miss your deadlines, and crash your tserver.  But only after letting
you think everything is fine for an hour or so.

Another example: accumulo will now detect configurations where
cache+memory-map > max memory.  Before, it would work for a while, and then
... slow death by stop-the-world garbage collection.  Better to detect it
up-front an not have to sherlock it from log files.

-Eric

On Thu, Jun 7, 2012 at 9:31 PM, Jim Klucar <kl...@gmail.com> wrote:

> I think that could be a slippery slope. We can't possibly support all
> the Linux settings required for optimal performance on all
> distributions.
>
> Sent from my iPhone
>
> On Jun 7, 2012, at 7:36 PM, David Medinets <da...@gmail.com>
> wrote:
>
> > I don't know the impact when this setting is too high. Apparently the
> > default in Ubuntu is 60. I only noticed the warning because I was
> > looking at log files randomly. I'm wondering if this check is
> > important enough to be done when the shell starts and to display the
> > error to the console at that time.
> >
> > This was the message:
> >
> > [server.Accumulo] WARN : System swappiness setting is greater than ten
> > (60) which can cause time-sensitive operations to be delayed.
> > Accumulo is time sensitive b
> > ecause it needs to maintain distributed lock agreement.
>

Re: System swappiness setting warning - important enough to display when shell starts?

[Jim Klucar <kl...@gmail.com>]

I think that could be a slippery slope. We can't possibly support all
the Linux settings required for optimal performance on all
distributions.

Sent from my iPhone

On Jun 7, 2012, at 7:36 PM, David Medinets <da...@gmail.com> wrote:

> I don't know the impact when this setting is too high. Apparently the
> default in Ubuntu is 60. I only noticed the warning because I was
> looking at log files randomly. I'm wondering if this check is
> important enough to be done when the shell starts and to display the
> error to the console at that time.
>
> This was the message:
>
> [server.Accumulo] WARN : System swappiness setting is greater than ten
> (60) which can cause time-sensitive operations to be delayed.
> Accumulo is time sensitive b
> ecause it needs to maintain distributed lock agreement.

Re: System swappiness setting warning - important enough to display when shell starts?

[Eric Newton <er...@gmail.com>]

The message makes it to the monitoring page and is displayed in scary
yellow.

I'm trying to turn all my support calls into "go to the monitoring page,
look for red or yellow."

-Eric

On Thu, Jun 7, 2012 at 7:41 PM, William Slacum <ws...@gmail.com> wrote:

> Personally, I like that non-deal-breaking settings are kept reasonably
> quiet at start up. In my dev environment I haven't run into an issue
> with it on Linux and have never messed with it on OSX.
>
> On Thu, Jun 7, 2012 at 7:36 PM, David Medinets <da...@gmail.com>
> wrote:
> > I don't know the impact when this setting is too high. Apparently the
> > default in Ubuntu is 60. I only noticed the warning because I was
> > looking at log files randomly. I'm wondering if this check is
> > important enough to be done when the shell starts and to display the
> > error to the console at that time.
> >
> > This was the message:
> >
> > [server.Accumulo] WARN : System swappiness setting is greater than ten
> > (60) which can cause time-sensitive operations to be delayed.
> > Accumulo is time sensitive b
> > ecause it needs to maintain distributed lock agreement.
>

Re: System swappiness setting warning - important enough to display when shell starts?

[William Slacum <ws...@gmail.com>]

Personally, I like that non-deal-breaking settings are kept reasonably
quiet at start up. In my dev environment I haven't run into an issue
with it on Linux and have never messed with it on OSX.

On Thu, Jun 7, 2012 at 7:36 PM, David Medinets <da...@gmail.com> wrote:
> I don't know the impact when this setting is too high. Apparently the
> default in Ubuntu is 60. I only noticed the warning because I was
> looking at log files randomly. I'm wondering if this check is
> important enough to be done when the shell starts and to display the
> error to the console at that time.
>
> This was the message:
>
> [server.Accumulo] WARN : System swappiness setting is greater than ten
> (60) which can cause time-sensitive operations to be delayed.
> Accumulo is time sensitive b
> ecause it needs to maintain distributed lock agreement.