Re: SWAP priority
Bob wrote: It became obvious after a short while, that I had too little physical memory (1GB), and I was using swap often. While swapping, things slowed down. So, I added an additional 1GB of swap space (via swap file) on the secondary file system. I did this as per the manual. I now have more swap; my question is this: How can I tell the OS to use the new swap file BEFORE using the old one? Is there a way to tell the system to prioritize the use of multiple swaps? The swap system knows how to interleave data between the additional swap areas relatively efficiently, but if your current workload is so demanding that you need to use more than 2GB of swapspace on a machine with 1GB of RAM, you should add more RAM, not more swapspace -- -Chuck ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: SWAP priority
On Monday 02 October 2006 09:14, Chuck Swiger wrote: The swap system knows how to interleave data between the additional swap areas relatively efficiently, Yes I discovered that. The additional swap space was instantly used as soon as I activated it; and the added swap improved things measurably. Does the swap system take into account current disk activity when it decides to use a particular swap? that you need to use more than 2GB of swapspace on a machine with 1GB of RAM, you should add more RAM, not more swapspace It is on order. The basis for my question about swap priority was based on an observation that the slowdown was due to swapping AND heavy disk usage. I noticed that when snapshots were being made on the main drive (the one I am using all the time), all other processes went to slow-mode. You see, the lack of enough memory caused the system to swap, and it swapped to the heaviest used raid array. I thought if I could force the system to swap to the other raid array (much less used) with the new swapfile, things would improve even more. All will be cured when more ram is installed, but I thought it would be interesting playing with swap priority. Bob ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: SWAP priority
On Oct 2, 2006, at 2:06 PM, Bob wrote: On Monday 02 October 2006 09:14, Chuck Swiger wrote: The swap system knows how to interleave data between the additional swap areas relatively efficiently, Yes I discovered that. The additional swap space was instantly used as soon as I activated it; and the added swap improved things measurably. Does the swap system take into account current disk activity when it decides to use a particular swap? Sort of. The syncer process runs at idle priority, so normal I/O initiated by your processes will take priority over paging/swapping idle pages of RAM out. There may be additional logic involved to help balance I/O in terms of which swapfile is being used if one drive remains busier than another, but I am not completely familiar with FreeBSD's implementation. that you need to use more than 2GB of swapspace on a machine with 1GB of RAM, you should add more RAM, not more swapspace It is on order. The basis for my question about swap priority was based on an observation that the slowdown was due to swapping AND heavy disk usage. I noticed that when snapshots were being made on the main drive (the one I am using all the time), all other processes went to slow-mode. You see, the lack of enough memory caused the system to swap, and it swapped to the heaviest used raid array. I thought if I could force the system to swap to the other raid array (much less used) with the new swapfile, things would improve even more. Well, you might try benchmarking the system with both arrays used for swapping and with only the less-busy RAID array being used for swapping, and see which one does better. -- -Chuck ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: SWAP priority
On Monday 02 October 2006 14:23, Charles Swiger wrote: Well, you might try benchmarking the system with both arrays used for swapping and with only the less-busy RAID array being used for swapping, and see which one does better. Yes, this is what I will do; if not benchmark, at least get a subjective feel for which is faster. Sorry to be a pest, but how can I do what you suggest? My SWAP0 is a _partition_ on the raid0 volume , and SWAP1 is a swapfile on raid1 created as a Vnode; and activated in rc.conf by swapfile=/raid1/swap1 How can I tell FreeBSD to ignore the primary swap partition? I set that partition up during the online install process if I recall, and none of my /etc/ files seem to reference it directly :-( I will also want to double the size of SWAP1 to 2GB, so the experiment is comparing the same swap space; but that part is simplistic. Bob ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: SWAP priority
On Mon, 2 Oct 2006 16:31:47 -0400
Bob [EMAIL PROTECTED] wrote:
Sorry to be a pest, but how can I do what you suggest? My SWAP0 is a
_partition_ on the raid0 volume , and SWAP1 is a swapfile on raid1 created
as a Vnode; and activated in rc.conf by swapfile=/raid1/swap1
How can I tell FreeBSD to ignore the primary swap partition? I set that
partition up during the online install process if I recall, and none of
my /etc/ files seem to reference it directly :-(
comment out the line swapfile in rc.conf .
B
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SWAP priority
Hi: OK, I have 2 swaps, one on the main raid (4 20GB hot-swap drives) 1/0 and another on the secondary (2 20GB hot-swap drives) raid 1. All hardware raid via dell PERC2 Controllers. This is on my personal work-station, which I am now using multi-tasking more then I have ever done. When I first installed the system I allocated SWAP as a seperate partition on the main (logical) drive equal to 2X my phisical memory. It became obvious after a short while, that I had too little physical memory (1GB), and I was using swap often. While swapping, things slowed down. So, I added an additional 1GB of swap space (via swap file) on the secondary file system. I did this as per the manual. I now have more swap; my question is this: How can I tell the OS to use the new swap file BEFORE using the old one? Is there a way to tell the system to prioritize the use of multiple swaps? Bob ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
