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Re: Fedora Bounties (seeking ideas)



Dnia 17-04-2006, pon o godzinie 21:45 -0400, seth vidal napisał(a):
> It just means we have to make an additional temp file and compare it
> every time. It costs time for the generic case where the files have
> changed and are newer. That being the most common case.
The most common case? Maybe if you use one server only. I use FC5
default config which uses a ton of mirrors. I am downloading "new"
version of the same repo's "primary.xml.gz" every half an hour (with
many versions spread among the mirrors) and other users are doing the
same thing. Yes, I know I can use "yum -C", but I really want to have
the newer data downloaded when I use yum list/yum install (which I do
pretty often), why can't I?

When I think about the cost I see one assembly jlt/jgt (how many CPU
cycles? ;)) to check if a timestamp is less (file is older) and issuing
a "move file" operation from (let's say) repomd.xml.tmp to repomd.xml,
which 1. is handled by kernel and kept in cache for a while, so no
slowup for yum and 2. "download xml.tmp;remove xml;move xml.tmp to xml"
instead of "remove xml;download xml" doesn't cost much more instructions
as I see it.

Oh, and last night I updated updates' cache with the updates at 1:00,
but wanted to download it when I sleep (86 MiB of updates after manually
taking pilot-link from updates-testing - this took over 2,5 hours on my
link), so (stupid me) instead of "yum -C" I did a "yum update" an hour
later.

Turned out there were three repo versions on the mirrors (with
primary.xml.gz having 122, 130 and 161 "k"B). I ended up doing "yum
clean all; yum update" (with only one repo enabled) for 10 straight
minutes just to see the data I already had over an hour earlier. It also
downloaded megabytes of useless data from the mirrors - to hell with my
link, but it costs the mirrors' bandwidth. All this IS a cost, but
simple "if timestamp2 > timestamp1" isn't.

I'm really not moaning, I can live with that until I get my hands on the
new apt, but I think about the others - why do they have to live with
it? :)

Lam

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