Date: Mon, 4 Mar 1996 21:02:38 +1100 From: Bruce Evans <bde@zeta.org.au> To: julian@ref.tfs.com, rashid@rk.ios.com Cc: hackers@FreeBSD.ORG Subject: Re: pwd_mkdb - really slow :( Message-ID: <199603041002.VAA05866@godzilla.zeta.org.au>
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>> I have quite afew systems here with ~10.00 accounts >> on ea ... and pwd_mkdb is _very slow now ... Takes >> 2+ minutes to rebuild the damn databases every time. I have only 14 accounts (12 distribution ones, bde and ftp), so I created dummy master.passwd files with thousands of accounts named "nobodyNNNNN" (NNNN = 0-29999) to test this. A real password file may take longer. On a P133, for 15014 accounts, `pwd_mkd -d /usr/tmp /usr/tmp/dummy_passwd' took about 39 seconds real, 3 user, 4 sys. For 30014 accounts, it took about 234 seconds real, 7 user, 16 sys. The main problem is obviously that the disk cache doesn't really work. ufs writes full blocks as soon as possible. This gives very poor performance for random writes if the same block is written many times. db often does this. I think it can be programmed to do more buffering in memory, but often isn't. kvm_mkdb was speeded up by a factor of about 5 by rewriting it to use mmap and more buffering; now it is only about twice as slow as the old version would be with a working disk cache ;-). >it might also be quicker to build the entire databse in ram >and bang it out to disk as a single write.. :) Not much, if write() is suitably buffered. Bruce
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