Re: Using XCode 3.1
Re: Using XCode 3.1
- Subject: Re: Using XCode 3.1
- From: Greg Guerin <email@hidden>
- Date: Fri, 18 Jul 2008 15:59:40 -0700
Rob Lockstone wrote:
I definitely agree with Jamie. Bring up the Activity Viewer and see
what Xcode might be doing in the background. Though, honestly, even
when it's indexing, it's not horrendously slow.
With "only" 2G of RAM, you might want to make sure you don't have
several other memory hogs running at the same that you're using
Xcode. And if your project, or the individual files you're editing,
are particularly large, that could contribute to slowness as well.
The main project I work on has maybe 10-12K files, but individual
files aren't generally more than a few thousand lines, and most
much smaller.
The main reason for adding RAM is if the machine is paging. If it's
not paging, then adding RAM won't make a significant performance
difference.
Activity Monitor.app can show paging and swapping (page-out/page-in)
activity.
First, under the System Memory tab there are cumulative numbers for
page-ins and page-outs. You'll want to watch these numbers, and also
watch the pie-chart of memory consumption. If you have free RAM,
your system is almost certainly not swapping. However, it may well
be doing page-ins, as the virtual-memory system loads disk files into
RAM on-demand. Once in memory (or just in disk cache), subsequent
reads should be very fast.
Second, you can infer page-ins and page-outs by watching the Disk
Activity tab, and correlating its graph to your expectation of disk
activity. If you expect there to be no disk activity, yet you see
some, then either your system is paging (in or out), or your
expectation is not taking everything into account. Small write
spikes are typically due to file-system syncing, so don't panic. If
the system is really being constrained by swapping or even paging-in,
it will usually appears as sustained disk activity during the periods
of slowness. If you see no disk activity at all, or only brief
spikes, then your system is unlikely to be constrained by disk speed,
hence not swap-limited.
Both observations are useful ways to compare what one expects to
happen against what really happens. For example, if you observe a
complete lack of disk activity and no page-ins, yet the system is
still slow, then VM paging is unlikely to be the cause of the
slowdown, and adding RAM is unlikely to help. Conversely, if
something shouldn't be consuming a lot of memory but really is, and
thus causing swapping, that will be evident in Disk Activity and
other graphs and indicators.
Finally, there is a useful command 'purge', that clears the disk
cache and as much other memory as possible. This often leads to a
burst of page-ins, but it's one way to see what happens when VM gets
purged.
-- GG
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