txn performance penalty

[Greg Louis]

>> Calendar time, on an otherwise idle machine with 512Mb RAM and 1Gb
>> swap, to process 545 spam starting after cold boot (memory is clear):
>>
>> 0.92.8: 51 seconds
>> 0.93.1 with defaults: 489 seconds
>> 0.93.1 with DB_TXN_NOT_DURABLE: 492 seconds
>>
>> This was with db-4.2.52.  Processing involved scoring each message
>> individually (with formail) and then scoring the same mbox with a
>> single bogofilter run (-vM).  The idea is to scan the spams and
>> register any false negatives, then rescan to check the result; but in
>> these runs there were no fn and so no messages were registered.

>I have just fed a large mailbox (1,050 messages) through bogofilter
>with
>formail -ds bogofilter <mbox, 
>
>0.93.1 took 28 s with default settings
>   CVS took 22 s with default settings
>   CVS took 15 s with --disable-transactions
>
>(arithmetic average of three runs with warm caches)

(1) my application, and the runs I quoted, were with the cache stone
cold :)

(2) having changed notebooks since then, I can no longer reproduce
these ridiculous times; I'm now getting, for 1457 spam, 19 seconds of
wall-clock time with 0.93.1 / qdbm, and 35 seconds with 0.93.1 / db
with transactions enabled.  Again, starting stone cold, ie right after
logging in after a reboot.

No idea what produced the difference.  Maybe I wrote the wordlist
directory for db_txn on a hunk of my 3-year-old HD that happened to
have a lot of soft errors?  Not very likely; nothing else seemed unduly
slow.

-- 
| G r e g  L o u i s         | gpg public key: 0x400B1AA86D9E3E64 |
|  http://www.bgl.nu/~glouis |   (on my website or any keyserver) |
|  http://wecanstopspam.org in signatures helps fight junk email. |