Re: Turn off Swap on boot disk
On 11/24/19 9:35 AM, Stuart Henderson wrote: On 2019-11-22, gwes wrote: First, why is your workload causing swapping? That hasn't been a good idea since the beginning of computing. Even if the main workload is OK, relinking the kernel (reorder_kernel) causes swapping on smaller-memory systems. Been there in 1980 on a KA-10. We fixed the linker to do multiple passes so it never had to have all the inputs in core at the same time. Not gonna happen to gnu ld. Just for giggles I split the link into 4 partials with -r then linked the partials with the low core. Reduced RSS from over 200M to about 80M. The output text size is identical. Unfortunately some bss allocation changed so I can't say the output is identical. That could be tracked down if there were any interest. Observation: ulimit -d 9 didn't change behavior even when dsize was well over 100. Or am I assuming wrong things? I've never seen an Alix so this may be impossible but why don't you install a larger boot drive? With how they're often used, it's usually easier to replace the whole machine. Maybe also cheaper, if they can be replaced by mailing a new machine rather than having to visit a remote site (swapping the CF card requires removing the system board from the case, not just opening the case). Adding swap on USB is one way to eke out another release or two's use from the machine that can be done fairly easily without a visit.. All very reasonable when the machine is in someone else's place. I'm thinking ahead about my little Edgerouter... will I have to replace that for 6.8? Will i386 die [well, it should have decades ago] Geoff Steckel
Re: Turn off Swap on boot disk
On 2019-11-22, gwes wrote: > First, why is your workload causing swapping? That hasn't been > a good idea since the beginning of computing. Even if the main workload is OK, relinking the kernel (reorder_kernel) causes swapping on smaller-memory systems. > I've never seen an Alix so this may be impossible but > why don't you install a larger boot drive? With how they're often used, it's usually easier to replace the whole machine. Maybe also cheaper, if they can be replaced by mailing a new machine rather than having to visit a remote site (swapping the CF card requires removing the system board from the case, not just opening the case). Adding swap on USB is one way to eke out another release or two's use from the machine that can be done fairly easily without a visit..
Re: Turn off Swap on boot disk
> On Nov 21, 2019, at 23:54, Theo de Raadt wrote: > > wait until you see the next thing i'm interested in. modern > machines will barely notice it, but alix's will quake. I look forward to what’s in store. As for all the other helpful comments (from Theo and others), thank you. The workload is non-critical, and I’m just trying to figure out the best trade-offs. If I felt the trade-offs weren’t worth it, I’d upgrade the machines. I feel I’m on the edge, and, yes, likely 6.7 will be the end of their usefulness. But I already own them, and they’re not useless yet. Sean
Re: Turn off Swap on boot disk
On 11/21/19 2:47 AM, Sean Kamath wrote: Hello. Can someone provide me a pointer to how to do this? I have a bunch of Alix 2d13 boxes. With 6.6, I’ve found I need more swap than the default layout on a 2G compact flash drive has. So, I got some 1G USB thumb drives, and want to use JUST those for swap. Despite different attempts (setting the mount_opts to xx, setting mount_opts to “priority=1”), I can’t seem to prevent the swap on the boot disk being added with priority = 0. Can I do anything to turn it off or change the priority, short of changing the filesystem type? Thanks, Sean I think you're trying to solve the wrong problem(s). First, why is your workload causing swapping? That hasn't been a good idea since the beginning of computing. Second, USB sticks are not designed to do frequent writes. If you need more swap space and have a USB port open, get a cheap 100G flash drive with a USB interface like a portable drive. I've never seen an Alix so this may be impossible but why don't you install a larger boot drive? Geoff Steckel i
Re: Turn off Swap on boot disk
Sebastien Marie wrote: > On Wed, Nov 20, 2019 at 11:47:39PM -0800, Sean Kamath wrote: > > Hello. > > > > Can someone provide me a pointer to how to do this? > > > > I have a bunch of Alix 2d13 boxes. With 6.6, I’ve found I need more swap > > than the default layout on a 2G compact flash drive has. So, I got some 1G > > USB thumb drives, and want to use JUST those for swap. Despite different > > attempts (setting the mount_opts to xx, setting mount_opts to > > “priority=1”), I can’t seem to prevent the swap on the boot disk being > > added with priority = 0. > > > > Can I do anything to turn it off or change the priority, short of changing > > the filesystem type? > > If I recall correctly, the swap on the boot disk is directly added by the > kernel, and not by rc(8). It is why priority in fstab(5) is ignored. config bsd swap generic It is part of the "swap generic" logic. > But you could change the priority of an already added swap with swapctl(8): > > # swapctl -c -p 1 myduid.b > > And you could automatically run it at boot-time by adding the command line in > /etc/rc.local file, which is sourced by rc(8). > > # echo 'swapctl -c -p 1 myduid.b' >> /etc/rc.local > > This way, at boot time: > - kernel adds the boot disk swap with priority 0 > - rc(8) adds the second swap with priority 0 (as configured in fstab(5)) > - rc(8) via rc.local changes the boot disk swap with priority 1 > - system will run with two swaps: > - second swap, priority 0, so used first > - boot disk swap, priority 1, used if second swap is full or by kernel for > dumping kernel core > > I hope it helps. It could help. Or, leave it alone. If you hit swap, you've learned something: Your machine is too small.
Re: Turn off Swap on boot disk
Sean Kamath wrote: > > On Nov 21, 2019, at 09:55, Kenneth Gober wrote: > > ... > > The need for more swap may be related to kernel relinking -- it might be an > > interesting experiment to see if your existing swap space is enough with > > kernel relinking disabled. > > Yes, precisely. > > I did add some larger CF cards on machines that needed more space. I just > happened to have a bunch of 1g thumb drives and figured I’d spare the CF all > the writes and use the thumbdrive. > > I was just hoping to avoid removing the default swap device so that in the > even the thumb drive died or whatever that the machine would still boot > (ideally, just setting the priority to 1 instead of 0 would do what I want). > > But, it sounds like the answer is delete/change the partition or live with > it. I’ll live with it, since I don’t want to disable kernel relinking. Sigh. relinking was added because risks have moved on, and smaller machines are less relevant. my first programming was on vic-20's. i wrote in basic. i ran out of space. then i wrote video games in a mix of asm and basic. then i ran out of space, and stored stuff in the unused nibbles of colour table. the lesson is eventually we need more, because we want to do more. we are now many decades later than the vic20, and arguably 2 decades after the best years of the alix. as a result, solutions using more resources to create benefits get added. wait until you see the next thing i'm interested in. modern machines will barely notice it, but alix's will quake.
Re: Turn off Swap on boot disk
On Wed, Nov 20, 2019 at 11:47:39PM -0800, Sean Kamath wrote: > Hello. > > Can someone provide me a pointer to how to do this? > > I have a bunch of Alix 2d13 boxes. With 6.6, I’ve found I need more swap > than the default layout on a 2G compact flash drive has. So, I got some 1G > USB thumb drives, and want to use JUST those for swap. Despite different > attempts (setting the mount_opts to xx, setting mount_opts to “priority=1”), > I can’t seem to prevent the swap on the boot disk being added with priority = > 0. > > Can I do anything to turn it off or change the priority, short of changing > the filesystem type? If I recall correctly, the swap on the boot disk is directly added by the kernel, and not by rc(8). It is why priority in fstab(5) is ignored. But you could change the priority of an already added swap with swapctl(8): # swapctl -c -p 1 myduid.b And you could automatically run it at boot-time by adding the command line in /etc/rc.local file, which is sourced by rc(8). # echo 'swapctl -c -p 1 myduid.b' >> /etc/rc.local This way, at boot time: - kernel adds the boot disk swap with priority 0 - rc(8) adds the second swap with priority 0 (as configured in fstab(5)) - rc(8) via rc.local changes the boot disk swap with priority 1 - system will run with two swaps: - second swap, priority 0, so used first - boot disk swap, priority 1, used if second swap is full or by kernel for dumping kernel core I hope it helps. -- Sebastien Marie
Re: Turn off Swap on boot disk
> On Nov 21, 2019, at 09:55, Kenneth Gober wrote: > ... > The need for more swap may be related to kernel relinking -- it might be an > interesting experiment to see if your existing swap space is enough with > kernel relinking disabled. Yes, precisely. I did add some larger CF cards on machines that needed more space. I just happened to have a bunch of 1g thumb drives and figured I’d spare the CF all the writes and use the thumbdrive. I was just hoping to avoid removing the default swap device so that in the even the thumb drive died or whatever that the machine would still boot (ideally, just setting the priority to 1 instead of 0 would do what I want). But, it sounds like the answer is delete/change the partition or live with it. I’ll live with it, since I don’t want to disable kernel relinking. Sean
Re: Turn off Swap on boot disk
On Thu, Nov 21, 2019 at 3:50 AM Sean Kamath wrote: > I have a bunch of Alix 2d13 boxes. With 6.6, I’ve found I need more swap > than the default layout on a 2G compact flash drive has. So, I got some 1G > USB thumb drives, and want to use JUST those for swap. Despite different > attempts (setting the mount_opts to xx, setting mount_opts to > “priority=1”), I can’t seem to prevent the swap on the boot disk being > added with priority = 0. > > Can I do anything to turn it off or change the priority, short of changing > the filesystem type? I wouldn't. The swap space is sometimes used for other things besides swap (like crash dumps) so why risk breaking something? Just add your thumb drive as additional swap space and leave it be. If it were me this would all be a temporary solution anyway while I acquire larger CF cards to switch to. I'm a huge fan of not getting rid of old stuff if it's still working, but when your needs outgrow your hardware, sometimes the simplest path forward is to just upgrade. The need for more swap may be related to kernel relinking -- it might be an interesting experiment to see if your existing swap space is enough with kernel relinking disabled. -ken
Turn off Swap on boot disk
Hello. Can someone provide me a pointer to how to do this? I have a bunch of Alix 2d13 boxes. With 6.6, I’ve found I need more swap than the default layout on a 2G compact flash drive has. So, I got some 1G USB thumb drives, and want to use JUST those for swap. Despite different attempts (setting the mount_opts to xx, setting mount_opts to “priority=1”), I can’t seem to prevent the swap on the boot disk being added with priority = 0. Can I do anything to turn it off or change the priority, short of changing the filesystem type? Thanks, Sean
