On Saturday, June 6, 2020 1:15:35 AM MST Samuel Sieb wrote: > On 6/6/20 12:42 AM, John M. Harris Jr wrote: > > > On my laptop, a Lenovo X200T with Core(TM)2 Duo CPU U9300; 6 GiB RAM, > > enabling swap on zram led to increased CPU usage (Always above 13% where > > normally idling at 6%!), and my entire system freezing after about 30 > > minutes. In all fairness, I don't know why my system froze, as I couldn't > > get anything over netconsole and sysrq wasn't working, but I think I'm > > going to leave it disabled. Swap on disk is more than fast enough for > > buffer/cache and hibernation/resume on my system. > > > I don't know why you had problems with it, but it's working on fine on > every system I've tried it on. It's not increasing my CPU usage. It's > probably actually lower due to less swap thrashing. There wasn't any thrashing to begin with. I'm currently using 8.0Mi of my 8 GiB of swap. This is most likely the case for most casual users, those not compiling complex software on their system. This is with Firefox, Konversation, KMail, virt-manager and a few Konsole sessions open. > > I don't know why people seem to be repeating what seems to be the result > > of a placebo, saying that their system "feels more responsive" with swap > > on zram. People seem to be forgetting why swap on zram came up to begin > > with, it has nothing to do with system "responsiveness", which wasn't an > > issue. It had to do with dealing with OOM. Swap on zram isn't even a > > solution to that, it just changes how specifically it affects systems. > > > See, this is a clear indication that you don't understand what it is > doing and weren't listening to the various people trying to explain it. > It is definitely not a placebo. I gave zram 5G out of the 12G I have > and my laptop is performing way better now. It's not thrashing the disk > (SSD) every time I switch desktops or windows. Due to the number and > size of applications I'm running, I normally have to close Thunderbird > when I want to run Chrome. But now I can start Chrome up with no > problem. I converted my running system with no reboots and I didn't > change anything else about how I'm using the laptop. > > # zramctl > NAME ALGORITHM DISKSIZE DATA COMPR TOTAL STREAMS MOUNTPOINT > /dev/zram0 lz4 5G 5G 1.7G 1.8G 4 > > 5GB of swap space that normally would be on disk is now taking less than > 2G of RAM. Instead of the usual 6G in the disk swap, now I have less > than 2. > > > > For servers, swap is useful regardless of the amount of RAM. Swap is very > > nice for use as buffer/cache, and leaves space in RAM for whatever the > > server is running. For example, I always configure a 4 GiB swap partition > > on servers with 8-24 GiB of RAM, and 8 GiB swap for servers with 64-128 > > GiB, 16 GiB on servers with 128-256 GiB, etc. Beyond that, tuning is a > > bit different depending on the workload, but it sets a very nice starting > > point. > > Swap is never used as buffer or cache, that doesn't even make sense. > Buffer is storing data before writing it to disk and cache is keeping > hot data somewhere with fast access. Why do you use so much swap on > your servers? The linear correlation with RAM is an obsolete idea and > was only somewhat valid when memory sizes were smaller. If you're using > any significant fraction of that swap space, your server is in trouble. It's not used for kernel buffer/cache, that's correct. -- John M. Harris, Jr. _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx
