Date: Sun, 23 Apr 2000 13:22:27 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Kent Stewart <kstewart@3-cities.com> Cc: Michael Bacarella <mbac@nyct.net>, Alfred Perlstein <bright@wintelcom.net>, Kevin Day <toasty@dragondata.com>, hackers@FreeBSD.ORG Subject: Re: Double buffered cp(1) Message-ID: <200004232022.NAA64183@apollo.backplane.com> References: <Pine.BSF.4.21.0004221320250.38433-100000@bsd1.nyct.net> <200004221736.KAA55484@apollo.backplane.com> <3901F277.66DDDDAF@3-cities.com> <200004222317.QAA56834@apollo.backplane.com> <39026874.F652A405@3-cities.com> <200004230625.XAA58076@apollo.backplane.com> <3902AEE3.C4E64476@3-cities.com> <200004231737.KAA62365@apollo.backplane.com> <3903563C.6453A9E2@3-cities.com>
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:>
:> I don't know what your setup is, Kent, but when I do a buildworld
:> my system is 95% cpu bound, with virtual no idle time at all. It's
:> all going to the buildworld. On both 3.x and 4.x.
:
:It is on 4.x but it wasn't on 3.4. At least, seti was taking time that
:it shouldn't have been getting.
Right. I think we're in agreement, it's just getting lost somewhere :-)
:> (For 3.x)
:>
:> CFLAGS= -O2 -pipe
:>
:> (For 4.x)
:>
:> CFLAGS= -Os -pipe
:
:I am trying this right now. I thought that optimizing this way was
:dangerous for the kernel. The problem for the new people is what works
:and when. You have to understand that Murphy sits on my shoulder. If
:there are 2+ bugs in a product, I will eventually end up seeing one of
:them :).
-O2 and -Os are 'safe'. Other optimization levels (-O3 for example)
are *NOT* safe. Most machine-specific optimizations (-m options) should
generally be considered NOT safe.
:I have been going to turn on softupdates but haven't got there yet. I
:want to link /usr/obj to the scsi drive first. Then, I think I will
:try softupdates. Try the worst combo's first and then add features but
:write the times down when you try the different arrangements.
:...
:Kent
I also turn off atime updates ('noatime' mount option in /etc/fstab)
on /usr/src, since buildworlds do a lot of file scanning and there
is simply no reason to update every single file's inode with a new
atime. I doubt it makes much of a difference but it does leave
more clean buffer cache buffers available for other things.
-pipe makes a significant difference since without it every source
file being compiled creates several files in /tmp. Softupdates makes
a significant difference in its ability to asynchronize file creation
and meta-data updates (which helps /tmp as well as /usr/obj, though
/tmp is helped even more by using -pipe).
-Matt
Matthew Dillon
<dillon@backplane.com>
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