Date: Thu, 27 Jan 2011 20:50:48 +0000 From: Devin Teske <dteske@vicor.com> To: Kostik Belousov <kostikbel@gmail.com> Cc: freebsd-hackers@freebsd.org, Mark Saad <nonesuch@longcount.org>, Teske <dteske@vicor.com>, Devin Subject: Re: rtld optimizations Message-ID: <1296161448.20060.40.camel@dt.vicor.com> In-Reply-To: <20110127203126.GN2518@deviant.kiev.zoral.com.ua> References: <AANLkTikwHteyqMfMpy_B-AxQ5ZQ_Z3RKhkNpGN23fXtX@mail.gmail.com> <20110125234911.223d8f75@kan.dnsalias.net> <201101271305.21510.naylor.b.david@gmail.com> <AANLkTinkhfso3iRR4pERxhf=%2BnCqy2YDigzgyfNVtnaJ@mail.gmail.com> <20110127203126.GN2518@deviant.kiev.zoral.com.ua>
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On Thu, 2011-01-27 at 22:31 +0200, Kostik Belousov wrote: > On Thu, Jan 27, 2011 at 12:37:54PM -0500, Mark Saad wrote: > > On Thu, Jan 27, 2011 at 6:05 AM, David Naylor <naylor.b.david@gmail.com> wrote: > > > On Wednesday 26 January 2011 06:49:11 Alexander Kabaev wrote: > > >> On Tue, 25 Jan 2011 21:40:42 -0500 > > >> > > >> Mark Saad <nonesuch@longcount.org> wrote: > > >> > Hello Hackers > > >> > > > >> > The NetBSD folks have a nice improvement with the rtld-elf subsystem, > > >> > known as "Negative Symbol Cache" . > > >> > > > >> > http://blog.netbsd.org/tnf/entry/netbsd_runtime_linker_gains_negative > > >> > > > >> > Roy Marples roy@ has a simple write up of the change. > > >> > > > >> > I took the basic idea from FreeBSD, but improved the performance > > >> > drastically. Basically, the huge win is by caching both breadth and > > >> > depth of the needed/weak symbol lookup. > > >> > Easiest to think of a,b,c,d as a matrix and FreeBSD just cache a row > > >> > where we cache both rows and columns. > > >> > > > >> > Has anyone looked into porting the changes back to FreeBSD ? The > > >> > improvement on load time for things like firefox, openoffice, and java > > >> > is huge on NetBSD. It looks like this change could improve load times > > >> > on FreeBSD in the same ways. > > >> > > >> This is a second time someone posts this to public mailing list and > > >> curiously enough is a second time it suggested that someone else is to > > >> do the investigation. From the quick look, the commit in question is > > >> more or less a direct rip-off of Donelists we had for ages and as > > >> such is completely over-hyped. The only extra quirk that said commit > > >> does is an optimization of a dlsym() call, which is hardly ever in > > >> critical performance path. Said optimization is trivial and easy to > > >> try. Here you have it: > > >> http://people.freebsd.org/~kan/rtld-symlook-depth.diff > > >> > > >> Since it only applies to dlsym, it only affects programs that are heavy > > >> plugin users, which I suppose is the category OpenOffice and firefox > > >> both fall into. Care to do some benchmarks with and without the > > >> patch and report the results? I frankly doubt that you'll see any > > >> noticeable difference compared to our stock rtld's performance. > > > > > > I benchmarked the impact said patch has on the boot-time of my system. I > > > timed the boot-time to when KDE launches autostart programs and once all > > > programs have loaded (I run a few extra programs, such as amarok). The latter > > > measure requires human action thus it has extra, human, variance in its > > > measure. > > > > > > I tried an older version of rtld (about 2 months old), current version of rtld > > > and the new (patched) rtld. I ran each test three times. There was little > > > variance in the tests and I am confident that there is no difference between > > > the different rtld versions and my boot-time. > > > > > > Here is a summary of my boot times (in seconds). First measure is when KDE > > > autostarts programs, the latter is when I determined when all programs had > > > launched. > > > rtld-old: 69 96 > > > rtld: 69 94 > > > rtld-new: 69 94 > > > > > > Please note that kernel boot time is approximately 10 seconds and kdm is > > > delayed by about 10 seconds thus 20 seconds can be removed from above numbers > > > to determine non-kernel boot wall-time. > > > > > > I would like to add that the blog entry claims a substantial improvement for > > > some use cases. Is it not worth to optimism these fringe cases as one mans > > > fringe case is another mans normal case (or woman as one prefers)? > > > > > > > > > So I figured out how to properly fit my foot in my mouth and set out > > to retesting this on netbsd. > > Turns out that in most cases the speed up is not as dramatic. > > > > Firefox 3.6.16 on amd64 > > > > old ld.elf_so: 4.07 seconds > > new ld.elf_so: 3.89 seconds > > > > Openoffice 3.1 on amd64 > > > > old ld.elf_so: 2.67 seconds > > new ld.elf_so: 2.60 seconds > > > > I am slightly perturbed that I can start openoffice faster then I can > > start firefox, oh well. > > Can you, please, satisfy my curiousity ? How did you fixated the moment > of finishing the startup of interactive applications like ff or oo ? Probably did something like this: time sh -c '( firefox & ); sleep 10000000' and then pressed Ctrl-C when he felt that firefox was finished loading. The moment Ctrl-C is pressed, time(1) shows how long it ran up until you pressed Ctrl-C. NOTE: Pressing Ctrl-C will not terminate the firefox instance. -- Devin
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