Received Fri 05 Oct 2007 4:13am +1000 from Jeff King: > On Thu, Oct 04, 2007 at 09:06:10PM +1000, Graham Williams wrote: > > > I've not been able to repeat. For example: > > > > $ time wajig new > > [27 packages] > > real 0m0.996s > > user 0m0.784s > > sys 0m0.336s > > $ > > > > Wajig is essentially doing the same as you suggest. I save the list of > > packages in ~/.wajig/Available and ~/.wajig/Available.prv. I extract > > (in python though) those in one and not in the other. Then list the > > results, getting the descriptions from dpkg and print them. > > > > Do you repeatably get the 1 minute execution? > > Yes, I do. If I run 'top' while doing the 'wajig new', it looks like all > of the CPU time is spent in a single egrep process. However, doing an > strace reveals that it is simply running > > egrep ^(Package|Status|Version): > > which seems reasonable. However, this is quite curious: > > $ time egrep '^(Package|Status|Version)' \ > </var/lib/dpkg/available \ > >~/egrep.out > real 1m21.106s > user 1m19.765s > sys 0m0.244s > > $ time perl -ne 'print if /^(Package|Status|Version)/' \ > </var/lib/dpkg/available \ > >perl.out > real 0m0.734s > user 0m0.628s > sys 0m0.096s > > $ cmp perl.out egrep.out && echo same > same > > IOW, egrep takes 110 times as long to produce the same output as perl. > So it looks like this is actually a serious performance regression in > egrep. Downgrading to 2.5.1.ds2-6 is much better (although it still > takes 3.2 seconds ot perl's .734!). > > So clearly this is an egrep bug, and should be reassigned. Although now > 'wajig new' still takes 3.3 seconds, which is a little sluggish. It > looks like the data passes through a mish-mash of shell tools, which we > can probably speed up a bit. Any interest in a patch?
Thanks for that Peff. A patch is most welcome. However, that is certainly very peculiar of egrep. I'm using the same version and see the opposite behaviour? $ time egrep '^(Package|Status|Version)' \ </var/lib/dpkg/available \ >| ~/egrep.out real 0m0.129s user 0m0.068s sys 0m0.028s $ time perl -ne 'print if /^(Package|Status|Version)/' \ </var/lib/dpkg/available \ >| perl.out real 0m0.500s user 0m0.452s sys 0m0.048s $ wajig status grep Package Installed Previous Now State =======================-===============-===============-===============-===== grep 2.5.3~dfsg-2 2.5.3~dfsg-2 2.5.3~dfsg-2 install $ wajig status perl Package Installed Previous Now State =======================-===============-===============-===============-===== perl 5.8.8-11 5.8.8-7 5.8.8-11 install Regards, Graham -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
