On Tue, 2014-04-01 at 16:15 -0400, KOSAKI Motohiro wrote: > >> Our middleware engineers has been complaining about this sysctl limit. > >> System administrator need to calculate required sysctl value by making sum > >> of all planned middlewares, and middleware provider needs to write "please > >> calculate systcl param by....." in their installation manuals. > > > > Why aren't people just setting the sysctl to a petabyte? What problems > > would that lead to? > > I don't have much Fujitsu middleware knowledges. But I'd like to explain > very funny bug I saw. > > 1. middleware-A suggest to set SHMMAX to very large value (maybe > LONG_MAX, but my memory was flushed) > 2. middleware-B suggest to set SHMMAX to increase some dozen mega byte. > > Finally, it was overflow and didn't work at all. > > Let's demonstrate. > > # echo 18446744073709551615 > /proc/sys/kernel/shmmax > # cat /proc/sys/kernel/shmmax > 18446744073709551615 > # echo 18446744073709551616 > /proc/sys/kernel/shmmax > # cat /proc/sys/kernel/shmmax > 0 hehe, what a nasty little tunable this is. Reminds me of this: https://access.redhat.com/site/solutions/16333 -- 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>