On Wednesday 22 March 2006 09:11, Chuck Swiger wrote: > Hi, Jason-- > > First, thanks for your work on the new jemalloc. > > Jason Evans wrote: > > On Mar 21, 2006, at 2:20 PM, John-Mark Gurney wrote: > [ ... ] > >> And yes, I'm pretty sure that I have a world from before your reduction > >> in chunk size... Having a minimum of a 6meg core doesn't sound like a > >> good idea... It's definately not going to play nice with small systems.. > > > > I don't think that a 6 MB core file is the big deal you are making it > > out to be. A 50 MB core file is a pain, mainly because it takes a long > > time to dump core. > > The smallest processes that people run often are likely going to be /bin/sh and > the typical fodder of shell scripts (grep, awk, and so forth). Under 4.x, > /bin/sh tended to have VSIZE of 640K and RSS of ~300K; under 5.x and later, > /bin/sh has VSIZE of 1.6MB and RSS of ~1MB. > > Creating a 50MB corefile from a 2MB VSIZE process is unreasonable. Creating a > 6MB corefile from a 2MB VSIZE process would be reasonable but probably could be > improved by a factor of two. > > On the other hand, the staticly linked "t" program is: > > chuck 62964 0.0 0.1 232 128 p0 TX 8:09AM 0:00.03 /tmp/t > > 128K RSS, 232 VSIZE. A 6MB corefile is a factor of 25 larger, which strikes me > as something that could be improved by more than a factor of ten. > > What else is being dumped that's not counted by VSIZE, aside from a header and > maybe some per-thread state, (although aren't the per-thread stacks already part > of VSIZE)...? > > Can jemalloc only create per-CPU arenas only for processes which are themselves > multithreaded, when it's running on a multi-CPU system? Would that help reduce > the amount of allocated but unreferenced memory that is involved for the common > case of /bin/sh and friends? I think the better path is to provide sparse coredumps. I.e., when dumping a core, leave the parts of the process map that are mapped but have no backing store yet (b/c the pages haven't been touched) sparse by not writing to them, but just seeking past them. This doesn't require complicating the malloc implementation just for the sake of a core dump on a CF device. -- John Baldwin <jhb_at_FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.orgReceived on Wed Mar 22 2006 - 14:20:06 UTC
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