search for: swappiness

Hi, I'm looking for a way to prevent qemu processes on a libvirt host to use swap unless there is no physical memory free but apparently this is not as easy as I'd hoped it would be. This is on a CentOS 7 system. At first I tried setting /proc/sys/vm/swappiness to 1 (apparently setting it to 0 now means even the OOM killer takes precedence over swapping: https://www.percona.com/blog/2014/04/28/oom-relation-vm-swappiness0-new-kernel/ ). After doing this I could still see the used swap increase for a guest even though there were 28G of memory used only as p...

...this behaviour to this extent/on so many servers. So you can say that I'm kind of a newbie in swapping ;) > If you don't explicitly lock things into memory, file I/O can and will > cause idle pages to get pushed out. It happens less often if you > manipulate swappines. So, is a swappiness value of 60 not recommended for servers? I worked with hundreds of servers (swappiness 60) on a social platform and swapping very rarely happened and then only on databases (which had swappiness set to 0). The only two differences (that I can see) to my current servers are that I used Debian an...

Hi All, I have a server that has its swappiness set to 0. It is running a little tight on memory and so there have been a couple of events where the OOM_killer has been invoked and killed off MySQL, which you would expect. Now if you have your swappiness at 0 then "A value of 0 instructs the kernel not to initiate swap until the amount of...

Hi all, This might not be CentOS related at all. Sorry about that. I have lots of C6 & C7 machines in use and all of them have the default swappiness of 60. The problem now is that a lot of those machines do swap although there is no memory pressure. I'm now thinking about lowering swappiness to 1. But I'd still like to find out why this happens. The only common thing between all those machines is that there are nightly backups done with...

..., I used to use centos 4.5 on an AMD 4800+ with 2GIG ram. Now I use centos 5.1 on AMD 6400+ with 4GIG RAM. The system responsiveness is different between the two. I noticed that centos 5.1 seems to be swapping programs out of memory at times resulting in slowness (perceived by me). I played with swappiness (/proc/sys/vm/) setting to 10, then 1 then 0. Still resulted in the same perceived slowness. Today I did swapoff -a and now the system obviously does not swap anything out all all. I thought thats what swappiness of 0 would have done. Are others experiencing this also? The perceived slowness maks...

...m and/or /proc/<pid>/smaps again. You can compare swap use before and after accessing the service to see how much was swapped out beforehand (presumably because of the backup), and how much had to be recovered for your test query. I'd suggest collecting that information at the normal swappiness setting and at 0. If the kernel is swapping out processes in favor of filesystem cache when swappiness is 0, I believe that would be a bug, and should be reported to the kernel developers. > Our salt-minion would be a candidate > for this. Allthough we constantly check if it's alive,...

...it's very low. AFAIK it's, as you already suggested, just that some (probably unused) parts are swapped out. But, some of those parts are the salt-minion, php-fpm or mysqld. All services which are important for us and which suffer badly from being swapped out. I already made some tests with swappiness 10 which mildly made it better. But there still was swap usage. So I tend to set swappiness to 1. Which I don't like to do, since those default values aren't there for nothing. Is it possible that this happens because the servers are VMs on an ESX-server. How could that affect this? How ca...

Am 05.06.2015 um 18:33 schrieb Gordon Messmer: > On 06/05/2015 03:29 AM, Markus "Shorty" Uckelmann wrote: >> some (probably unused) parts are swapped out. But, some of >> those parts are the salt-minion, php-fpm or mysqld. All services which >> are important for us and which suffer badly from being swapped out. > > Those two things can't really both be

On 04.06.2015 22:18, Markus "Shorty" Uckelmann wrote: > Hi all, > > This might not be CentOS related at all. Sorry about that. > > I have lots of C6 & C7 machines in use and all of them have the default > swappiness of 60. The problem now is that a lot of those machines do > swap although there is no memory pressure. I'm now thinking about > lowering swappiness to 1. But I'd still like to find out why this > happens. The only common thing between all those machines is that there > are night...

On 09/16/2015 09:11 AM, Callum Scott wrote: > It is running a little > tight on memory and so there have been a couple of events where the > OOM_killer has been invoked and killed off MySQL, which you would expect. One thing that should be noted is that regardless of swappiness, overcommit might be an issue. If a single process is using most of the memory in a system, and attempts to fork(), as it will if it calls system(), then the system may require that there is enough memory for a second instance of that huge process. This is one of the reasons why swap should b...

...id>/smaps again. > You can compare swap use before and after accessing the service to > see how much was swapped out beforehand (presumably because of the > backup), and how much had to be recovered for your test query. > > I'd suggest collecting that information at the normal swappiness > setting and at 0. Thank you, this will get me further. > If the kernel is swapping out processes in favor of filesystem > cache when swappiness is 0, I believe that would be a bug, and > should be reported to the kernel developers. Because of what I read in [2] I'm not planning...

.../2015 09:11 AM, Callum Scott wrote: >> It is running a little >> tight on memory and so there have been a couple of events where the >> OOM_killer has been invoked and killed off MySQL, which you would >> expect. > > One thing that should be noted is that regardless of swappiness, > overcommit might be an issue. If a single process is using most of the > memory in a system, and attempts to fork(), as it will if it calls > system(), then the system may require that there is enough memory for a > second instance of that huge process. > > This is one of the...

...tcp_rmem = 1048576 4194304 16777216 net.ipv4.tcp_wmem = 1048576 4194304 16777216 # Disable netfilter on bridges. net.bridge.bridge-nf-call-ip6tables = 0 net.bridge.bridge-nf-call-iptables = 0 net.bridge.bridge-nf-call-arptables = 0 # Virtual machines special kernel params vm.swappiness = 0 Do I need to configure something more?? Any tips?? Thanks. -- CL Martinez carlopmart {at} gmail {d0t} com

On 06/05/2015 03:29 AM, Markus "Shorty" Uckelmann wrote: > some (probably unused) parts are swapped out. But, some of > those parts are the salt-minion, php-fpm or mysqld. All services which > are important for us and which suffer badly from being swapped out. Those two things can't really both be true. If the pages swapped out are unused, then the application won't

On Fri, Jun 05, 2015 at 12:29:04PM +0200, Markus "Shorty" Uckelmann wrote: > How can I further debug this > problem and find out what's the culprit? It's working as designed. Linux does not treat various kinds of memory pages differently. If you want a daemon to be fully in core, call mlockall(). Here's one way to do that without changing the daemon's source:

On 05.06.2015 19:47, Greg Lindahl wrote: > On Fri, Jun 05, 2015 at 09:33:11AM -0700, Gordon Messmer wrote: >> On 06/05/2015 03:29 AM, Markus "Shorty" Uckelmann wrote: >>> some (probably unused) parts are swapped out. But, some of >>> those parts are the salt-minion, php-fpm or mysqld. All services which >>> are important for us and which suffer badly

On Wed, 2015-09-16 at 13:36 -0400, m.roth at 5-cent.us wrote: > Excerpt on heavy-duty servers. We're certainly not going to allocate > hundreds of gigs, or a terabyte or so, for swap. (Yes, we do have servers > with that kind of RAM, and that's not counting the small SGI > supercomputer....) Do you really run Centos on the SGI ? -- Regards, Paul. England, EU.

...tc/sysctl.d/ On Thu, Dec 24, 2015 at 8:58 AM, Gordon Messmer <gordon.messmer at gmail.com> wrote: > On 12/23/2015 05:08 AM, Ofer Hasson wrote: > >> By running "systemctl status systemd-sysctl" I also receive the same >> output, but a simple "cat /proc/sys/vm/swappiness" returns the default >> value, and not the one set by my conf file. >> > > All of mine, as set by files in /etc/sysctl.d/, are correct after boot. > Where is your conf file? > > _______________________________________________ > CentOS mailing list > CentOS at c...

On 06.06.2015 04:48, Dennis Jacobfeuerborn wrote: > On 05.06.2015 19:47, Greg Lindahl wrote: >> On Fri, Jun 05, 2015 at 09:33:11AM -0700, Gordon Messmer wrote: >>> On 06/05/2015 03:29 AM, Markus "Shorty" Uckelmann wrote: >>>> some (probably unused) parts are swapped out. But, some of >>>> those parts are the salt-minion, php-fpm or mysqld. All

On Fri, Jun 05, 2015 at 09:33:11AM -0700, Gordon Messmer wrote: > On 06/05/2015 03:29 AM, Markus "Shorty" Uckelmann wrote: > >some (probably unused) parts are swapped out. But, some of > >those parts are the salt-minion, php-fpm or mysqld. All services which > >are important for us and which suffer badly from being swapped out. > > Those two things can't