At Sun, 16 Jan 2005 20:55:28 +0100, Falk Hueffner wrote: > Marcelo E. Magallon writes: > > > On Sat, Jan 15, 2005 at 10:14:15PM +0900, GOTO Masanori wrote: > > > > > > occurs when you have for example an ev56 library in lib/ev56, and a > > > > ev67 CPU. Then the loader looks in lib/ev67 and then falls back to > > > > lib. Since glibc is very carefully undocumented in this area [1], I > > > > didn't want to try to change this, but rather assumed one could add > > > > a symlink. > > > > > > Yes, and if ev67 is instruction upper compatible with ev56 (I guess > > > so), I think it's acceptable to add a symlink "ln -sf > > > lib/ev67/libfoo.so lib/ev56/libfoo.so". > > > > Ugh... that pushes the burden of maitaining support for new > > architectures to the package.
Yeah - I think it's trade off - whether we support library optimization package or we don't get a bit performance improvement. > > Please bear with me, but I'm trying > > to understand the issue: is the cost of calling access(2) or stat(2) > > really so high? > > I'd consider it quite acceptable in this case. However, as I tried to > express, it's not possible with glibc's current "design", and I didn't > feel like changing that. Note that we should keep in mind: imagine most binaries on all debian system over the world start to consume access(2)/stat(2) system call cost in each binary execution time - "Many a little makes a mickle". > > I see for example that on start up the file /etc/ld.so.nohwcap is > > accessed multiple times (and it's not present, isn't that a race? > > what happens if the file suddenly appears in the middle of program > > start up? what's that file anyway, I can't find it mentioned in the > > documentation). > > It's supposed to disable the use of hwcaps. Stating it multiple times > seems like a bug. Debian glibc has been applied a special patch to check /etc/ld.so.nohwcap before loading libraries each time. You can see it in debian-glibc package ldso-disable-hwcap.dpatch written by Ben and Daniel. It enables us to upgrade smoothly even if we use optimized libraries - this effort is one of debian's nice features. But the drawback is it needs to pay access(2) lookup cost as you pointed out. Checking /etc/ld.so.nohwcap each time (some binaries call multiple times) is the current patch design - I think this is safer than checking /etc/ld.so.nohwcap once in program startup time. However, yes, it affects execution time for short life programs. I think it's acceptable because it's one of debian's nice feature... Regards, -- gotom -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
