On Sat 06-01-18 19:03:13, Sergey Senozhatsky wrote: > Hello, > > On (01/06/18 10:41), Michal Hocko wrote: > > On Sat 06-01-18 13:34:07, Sergey Senozhatsky wrote: > > > Use the ratelimited printk() version for swap-device write error > > > reporting. We can use ZRAM as a swap-device, and the tricky part > > > here is that zsmalloc() stores compressed objects in memory, thus > > > it has to allocates pages during swap-out. If the system is short > > > on memory, then we begin to flood printk() log buffer with the > > > same "Write-error on swap-device XXX" error messages and sometimes > > > simply lockup the system. > > > > Should we print an error in such a situation at all? Write-error > > certainly sounds scare and it suggests something went really wrong. > > My understading is that zram failed swap-out is not critical and > > therefore the error message is not really useful. > > I don't mind to get rid of it. up to you :) I do not think we can get rid of it for all swap backends. > > Or what should an admin do when seeing it? > > zsmalloc allocation is just one possibility; an error in > compressing algorithm is another one, yet is rather unlikely. > most likely it's OOM which can cause problems. but in any case > it's sort of unclear what should be done. an error can be a > temporary one or a fatal one, just like in __swap_writepage() > case. so may be both write error printk()-s can be dropped. Then I would suggest starting with sorting out which of those errors are critical and which are not and report the error accordingly. I am sorry to be fuzzy here but I am not familiar with the code to be more specific. Anyway ratelimiting sounds more like a paper over than a real solution. Also it sounds quite scary that you can see so many failures to actually lock up the system just by printing a message... -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
