Re: [CentOS] Memory Usage in Top and System Monitor
On 07/21/2011 04:57 PM, Michael McNulty wrote: > > Yes I am copying files there but as my first post shows I have plenty of free > memory so I thought it should not be using swap space. > > I guess this is my problem. > http://www.cyberciti.biz/faq/howto-create-linux-ram-disk-filesystem/ > > "tmpfs (also known as > shmfs) is a little different from the Linux ramdisk. It allocate memory > dynamically and by allowing less-used pages to be moved onto swap space. > ramfs, in contrast, does not make use of swap which can be an advantage > or disadvantage in many cases." > > So it looks like I need to use "ramfs" as described here? That sound about > right? A ramfs is still using memory. If the remaining memory is inadequate to satisfy the needs of processes, _something_ is going to be forced out to swap. Since that won't be the pages used by the ramfs, it will be pages in use by processes. Whether that is better or worse, from a performance standpoint, than swapping out pages from your tmpfs files is something you would have to determine, but there is no free lunch here. One thing that may be confusing your view of free memory is that a tmpfs uses pages from the buffer cache, and the 'free' command shows that usage in the "cached" category. (No, I didn't realize that, either.) This is a place where pages listed as "cached" are _not_ available to satisfy processes' memory requests. It looks like you need to run "df -t tmpfs" and add up the numbers in the "Used" column to see how much memory falls in the category of "looks like cached, but can't be discarded." -- Bob Nichols "NOSPAM" is really part of my email address. Do NOT delete it. ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Memory Usage in Top and System Monitor
Yes I am copying files there but as my first post shows I have plenty of free memory so I thought it should not be using swap space. I guess this is my problem. http://www.cyberciti.biz/faq/howto-create-linux-ram-disk-filesystem/ "tmpfs (also known as shmfs) is a little different from the Linux ramdisk. It allocate memory dynamically and by allowing less-used pages to be moved onto swap space. ramfs, in contrast, does not make use of swap which can be an advantage or disadvantage in many cases." So it looks like I need to use "ramfs" as described here? That sound about right? > To: centos@centos.org > From: rnicholsnos...@comcast.net > Date: Thu, 21 Jul 2011 16:28:15 -0500 > Subject: Re: [CentOS] Memory Usage in Top and System Monitor > > On 07/21/2011 03:20 PM, Michael McNulty wrote: > > > > --- On Thu, 7/21/11, Robert Nichols wrote: > > > >> Perhaps by not storing so much stuff in it? That, or > >> adding more RAM. Seriously, if you're going to fill up a large portion of > >> your available memory with a ramdisk, demands for memory are going to have > >> to be met by pushing pages out to swap space. By default, a > >> ramdisk can grow to up to half of the available RAM after the kernel has > >> been > >> loaded. If programs and I/O buffers need more than the other memory > >> you have available, what option is there besides swap? > >> > > > > Actually I am not storing too much stuff in it since there is plenty of > > free memory. That was the point of my earlier posts asking why swap when > > there is plenty of free memory. > > > > Correct me if I am wrong, but I believe behavior is unused files in > > /dev/shm use swap space? I want to make it so it does not do that since it > > slows the system down > > and since there is plenty of available free memory. > > A ramdisk does not consume any memory at all until you store stuff > in it, and then it uses only such memory as is required to hold its > current contents, i.e., it will shrink again if stored files are > truncated or removed. From your comment, I presumed you knew you > were actually storing data in /dev/shm. If you are not, then you > will have to look elsewhere to see what is sometimes consuming a lot > of memory. > > -- > Bob Nichols "NOSPAM" is really part of my email address. > Do NOT delete it. > > ___ > CentOS mailing list > CentOS@centos.org > http://lists.centos.org/mailman/listinfo/centos ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Memory Usage in Top and System Monitor
On 07/21/2011 03:20 PM, Michael McNulty wrote: > > --- On Thu, 7/21/11, Robert Nichols wrote: > >> Perhaps by not storing so much stuff in it? That, or >> adding more RAM. Seriously, if you're going to fill up a large portion of >> your available memory with a ramdisk, demands for memory are going to have >> to be met by pushing pages out to swap space. By default, a >> ramdisk can grow to up to half of the available RAM after the kernel has been >> loaded. If programs and I/O buffers need more than the other memory >> you have available, what option is there besides swap? >> > > Actually I am not storing too much stuff in it since there is plenty of free > memory. That was the point of my earlier posts asking why swap when there is > plenty of free memory. > > Correct me if I am wrong, but I believe behavior is unused files in /dev/shm > use swap space? I want to make it so it does not do that since it slows the > system down > and since there is plenty of available free memory. A ramdisk does not consume any memory at all until you store stuff in it, and then it uses only such memory as is required to hold its current contents, i.e., it will shrink again if stored files are truncated or removed. From your comment, I presumed you knew you were actually storing data in /dev/shm. If you are not, then you will have to look elsewhere to see what is sometimes consuming a lot of memory. -- Bob Nichols "NOSPAM" is really part of my email address. Do NOT delete it. ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Memory Usage in Top and System Monitor
Sorry, I am new to using the mailing list. I put RE: in the subject line thinking it would stay in the same thread but not sure why it did not work. So I turned of daily digest to reply and replying directly now. Apologies if this reply did not work. > Date: Thu, 21 Jul 2011 22:35:47 +0200 > From: office@plnet.rsSend > To: centos@centos.org > Subject: Re: [CentOS] Memory Usage in Top and System Monitor > > Michael McNulty wrote: > > --- On Thu, 7/21/11, Robert Nichols wrote: > > > >> Perhaps by not storing so much stuff in it? That, or > >> adding more RAM. Seriously, if you're going to fill up a large portion of > >> your available memory with a ramdisk, demands for memory are going to have > >> to be met by pushing pages out to swap space. By default, a > >> ramdisk can grow to up to half of the available RAM after the kernel has > >> been > >> loaded. If programs and I/O buffers need more than the other memory > >> you have available, what option is there besides swap? > >> > > > > Actually I am not storing too much stuff in it since there is plenty of > > free memory. That was the point of my earlier posts asking why swap when > > there is plenty of free memory. > > > > Correct me if I am wrong, but I believe behavior is unused files in > > /dev/shm use swap space? I want to make it so it does not do that since it > > slows the system down > > and since there is plenty of available free memory. > > > > ___ > > CentOS mailing list > > CentOS@centos.org > > http://lists.centos.org/mailman/listinfo/centos > > Could you please use regular reply option? I can now see 3 separate > threads with the same name,and they are only your thread(s). Thanks > > -- > > Ljubomir Ljubojevic > (Love is in the Air) > PL Computers > Serbia, Europe > > Google is the Mother, Google is the Father, and traceroute is your > trusty Spiderman... > StarOS, Mikrotik and CentOS/RHEL/Linux consultant > ___ > CentOS mailing list > CentOS@centos.org > http://lists.centos.org/mailman/listinfo/centos ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Memory Usage in Top and System Monitor
Michael McNulty wrote: > --- On Thu, 7/21/11, Robert Nichols wrote: > >> Perhaps by not storing so much stuff in it? That, or >> adding more RAM. Seriously, if you're going to fill up a large portion of >> your available memory with a ramdisk, demands for memory are going to have >> to be met by pushing pages out to swap space. By default, a >> ramdisk can grow to up to half of the available RAM after the kernel has been >> loaded. If programs and I/O buffers need more than the other memory >> you have available, what option is there besides swap? >> > > Actually I am not storing too much stuff in it since there is plenty of free > memory. That was the point of my earlier posts asking why swap when there is > plenty of free memory. > > Correct me if I am wrong, but I believe behavior is unused files in /dev/shm > use swap space? I want to make it so it does not do that since it slows the > system down > and since there is plenty of available free memory. > > ___ > CentOS mailing list > CentOS@centos.org > http://lists.centos.org/mailman/listinfo/centos Could you please use regular reply option? I can now see 3 separate threads with the same name,and they are only your thread(s). Thanks -- Ljubomir Ljubojevic (Love is in the Air) PL Computers Serbia, Europe Google is the Mother, Google is the Father, and traceroute is your trusty Spiderman... StarOS, Mikrotik and CentOS/RHEL/Linux consultant ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Memory Usage in Top and System Monitor
On 07/20/2011 07:09 PM, Michael McNulty wrote: > I think I found my problem. I did not realize using /dev/shm as a ramdisk will > create swap space. Is there a way to prevent the ramdisk from swapping to > disk? Perhaps by not storing so much stuff in it? That, or adding more RAM. Seriously, if you're going to fill up a large portion of your available memory with a ramdisk, demands for memory are going to have to be met by pushing pages out to swap space. By default, a ramdisk can grow to up to half of the available RAM after the kernel has been loaded. If programs and I/O buffers need more than the other memory you have available, what option is there besides swap? -- Bob Nichols "NOSPAM" is really part of my email address. Do NOT delete it. ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Memory Usage in Top and System Monitor
I think I found my problem. I did not realize using /dev/shm as a ramdisk will create swap space. Is there a way to prevent the ramdisk from swapping to disk? ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
