[Digikam-users] New computer for Digikam

[Gerhard Kulzer]

Am Saturday 08 December 2007 schrieb Gilles Caulier:
> 2007/12/8, Gerhard Kulzer <gerhardkgmx at gmail.com>:
> > Am Saturday 08 December 2007 schrieb Dotan Cohen:
> > > On 08/12/2007, Mikolaj Machowski <mikmach at wp.pl> wrote:
> > > > Dnia Saturday 08 of December 2007, Dotan Cohen napisał:
> > > > > I am considering replacing an aging desktop computer. The machine
> > > > > is used mostly for Digikam, Amarok, and Kopete. Only occasionally
> > > > > are other apps, such as K3B, Firefox, Skype, and Open Office ever
> > > > > used. Therefore, I want a system that is tuned best for Digikam.
> > > >
> > > > digiKam can only gain from faster disks, memory and processor. Next
> > > > version of KDE can gain from better graphic card due to increase
> > > > usage of OpenGL effects but I am not aware about usage of those in
> > > > digiKam - now or in near future (apart from slideshows).
> > >
> > > Thanks, Mikolaj. I just wanted to know where I should be careful not
> > > to bottleneck. A 3.6 GHz processor would be a waste if the system had
> > > only 256MB RAM (extreme example).
> > >
> > > Do factors such as bus speed, L2 cache, number of cores, and speed of
> > > RAM make a significant difference for Digikam specifically? I know
> > > that it seems like a silly question, but if I'm buying hardware for a
> > > specific purpose, I'd like to get the right hardware. And I _will_
> > > have to make compromises as budget allows. Where should those
> > > compromises be?
> > >
> > > Thanks.
> > >
> > > Dotan Cohen
> >
> > Right now digiKam is not yet taking much advantage of smp for the
> > heavy-load
> > plugins (CIMG), but that will change in the future, so a dual processor
> > is recommended, although not fully exploited today. There are a lot of
> > tasks running in threads by now, but those are not the time consumers. If
> > you planned for today only, a fast single CPU would be better, but I
> > don't recommend it. Don't buy a dual core machine that is too slow in
> > clock.
>
> I'm not agree. A dual core is a 2 processors in same core.
>
> DigiKam use multithreading everywhere when it's possible : compute or
> loading image for ex.
>
> With a dual core, the main thread (GUI) will run on first processor, and
> child thread will run on second processor. if clock speed is more slow than
> a fast single core processor, there is a real advantage to fork sub-tasks
> on a separate processor...
>
>  Currently, CImg based plugins use 2 sub-threads to work. This is perfectly
> adapted to dual core...

I made several tests, Gilles. It's true that CIMG splits in two threads, but 
the load never exceeds 50% per thread. So it's the same as if it was running 
in one thread. I test with htop.

> I always recommend to use :
>
> - Intel processor instead AMD (Gcc give better result especially about
> speed)
> - 32 bits processors. 64 bits is a mess under Linux. 64 bits library need
> to use a 32 bits emulation like to run...
>
> In my office, we have 3 bigs computers using 48 / 64 / and 128 processors
> and running under linux. It's used by physicians to calc thermonuclear
> reaction simulation codes...
>
> The first one is an old Alpha processor based computer. Very fast
> The second one an AMD 64 bits processor.
> The third is a 32 bits Intel based processor.
>
> The AMD based give less speed result than Alpha and Intel computer.
>
> Gilles
>
> Intels
>
> > can be overclocked, but you need the MB that goes with it. L2 cache is
> > quite
> > important in my experience. Two cores is fantastic even if you don't run
> > many
> > applications in parallel. I just enjoy my machine churning on digiKam
> > stuff
> > and still be reactive as nothing would happen in the background :-), it's
> > impressive.
> > My CPU recommendation is Intel E6750, that is really cheap for what it
> > is, cheaper than slower CPUs. But you need an 1333MHz FSB motherboard.
> > I'd recommend that anyway, because if you want to upgrade later, the CPUs
> > are likely to run at least that fast (I just sold my E6400 CPU on ebay
> > for 98% of
> > the price I bought it a year ago, upgrading is possible).
> > Buy enough memory, 1GB is not enough, buy >=2GB. The memory speed is not
> > so
> > important, between the slow ones and fast one there is hardly 10%
> > difference
> > in endperformance.
> > SATA or ATA, my hdparm tests don't show much of a difference. But modern
> > MB
> > will oblige you to go SATA-II. The file system makes more of a diff, not
> > for
> > saving the images, but for the thumbnails caching. Mount them with
> > 'noatime'.
> > Without journal is much faster. Better is (you seem to have two disks) to
> > put
> > the journal of one disk on the other drive. Speed is then as a fs without
> > journaling because of the parallel access. xfs, reiserfs or ext3 are all
> > good.
>
> I have always use reiser FS under Linux. It's probably the best...
>
>
> digiKam don't ask much of graphic cards. But nowadays even good ones are
>
> > cheap, I bought a nvidia NT8600GT for less than 100 euros, has 260MB RAM,
> > passively cooled. And I wouldn't want to miss compiz anymore.
> > Think rather of a good monitor, we had this discussion already on this
> > ML. Photos require an excellent screen, notbooks are no good in general.
>
> In my office i always use ATI card. Pro-drivers are better quality than
> NVidia, especially to use OpenGL (with slideshow plugin for ex.)
>
> Gilles



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