Thread: RE: Expectations of MEM requirements for a DB with
>> Anyway, I crashed my system the other day when I did a "select *" from >> one >> of my large tables (about 5.5gb in size). > > Well.... It takes abit more than that to actually crash the system. Can >you give more details? What _exactly_ happened? Did it hang? Kernel >panicked? Something else. Actually, I was watching this convo on another message board. When linux hits low memory situations (i.e. none) it thrashes for far longer than it should have to, just to free some up. In this way, NT and other OS's are much better - they can run with no memory available, very slowly, but without waiting 2 hours for processes to time out. For all intents and purposes, you will get your box back quicker with linux by rebooting than waiting a few hours for it to respond. I'm not posting that here as a gripe, but to support the guy who said it "crashed". Rob Nelson rdnelson@co.centre.pa.us
Thats very true. FreeBSD is a little smarter, and actualy kills a runaway process if it allocates more memory than is available. It of course tries to page things in and out of swap first, hoping the high memory condition will soon resolve its self. FreeBSD is also one of the only OSes I've seen that kick processes (idle ones, i.e., cron, getty, etc) out of memory for kernel buffers and disk cache to improve preformance for busier ones. Yann On Mon, 06 Nov 2000, you (Robert D. Nelson) might of written: > Actually, I was watching this convo on another message board. When linux > hits low memory situations (i.e. none) it thrashes for far longer than it > should have to, just to free some up. In this way, NT and other OS's are > much better - they can run with no memory available, very slowly, but > without waiting 2 hours for processes to time out. For all intents and > purposes, you will get your box back quicker with linux by rebooting than > waiting a few hours for it to respond. I'm not posting that here as a > gripe, but to support the guy who said it "crashed". > > > Rob Nelson > rdnelson@co.centre.pa.us -- -------------------------------------------------------------------- Yann Ramin atrus@atrustrivalie.eu.org Atrus Trivalie Productions www.redshift.com/~yramin AIM oddatrus Marina, CA http://profiles.yahoo.com/theatrus IRM Developer Network Toaster Developer SNTS Developer KLevel Developer Electronics Hobbyist person who loves toys Build a man a fire, and he's warm for a day. Set a man on fire, and he'll be warm for the rest of his life. "I'm prepared for all emergencies but totally unprepared for everyday life." --------------------------------------------------------------------
On Mon, Nov 06, 2000 at 07:45:10PM -0800, Yann Ramin wrote: > FreeBSD is also one of the only OSes I've seen that > kick processes (idle ones, i.e., cron, getty, etc) out of memory for kernel > buffers and disk cache to improve preformance for busier ones. Linux also does this, and has does this for quite some time: USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 417 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] root 418 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] root 419 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] root 420 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] root 421 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] root 422 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] root 429 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] root 430 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] bruce 431 0.0 0.0 2588 0 ? SW Sep06 0:00 [pyhttpd2] root 432 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] root 433 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] root 435 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] root 440 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] root 441 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] root 442 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] root 443 0.0 0.0 1084 0 ? SW Sep06 0:00 [supervise] root 714 0.0 0.0 1364 0 ? SW Sep06 0:18 [junkbuster] root 759 0.0 0.0 3252 0 ? SW Sep06 0:00 [python] root 782 0.0 0.0 1688 0 ? SW Sep06 0:00 [safe_mysqld] root 869 0.0 0.0 2196 0 tty1 SW Sep06 0:00 [login] root 872 0.0 0.0 2196 0 tty4 SW Sep06 0:00 [login] root 873 0.0 0.0 2196 0 tty5 SW Sep06 0:00 [login] root 2007 0.0 0.0 2196 0 tty2 SW Sep07 0:00 [login] root 2010 0.0 0.0 2196 0 tty3 SW Sep07 0:00 [login] postgres 12527 0.0 0.0 5508 0 ? SW Sep09 0:00 [postmaster] root 24968 0.0 0.0 2188 0 tty6 SW Sep13 0:00 [login] lori 26328 0.0 0.0 1712 0 tty1 SW Sep13 0:00 [bash] root 22233 0.0 0.0 1084 0 ? SW Sep12 0:00 [unixserver] bruce 19645 0.0 0.0 1976 0 ? SW Sep18 0:00 [vpyadmin-sessio] root 7411 0.0 0.0 1176 0 ? SW Sep23 0:00 [lpd] root 31969 0.0 0.0 1120 0 ? SW Sep24 0:00 [inetd] root 32052 0.0 0.0 2644 0 ? SW Sep30 0:00 [xdm] root 5925 0.0 0.0 3568 0 ? SW Oct23 0:00 [xdm] lori 31163 0.0 0.0 1708 0 pts/2 SW Oct27 0:00 [bash] -- Bruce Guenter <bruceg@em.ca> http://em.ca/~bruceg/