Messages in this thread | | | Date | Mon, 25 May 2009 21:39:08 +0300 | From | Pekka Enberg <> | Subject | Re: [GIT PULL] scheduler fixes |
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Hi Linus,
Linus Torvalds wrote: > On Mon, 25 May 2009, Pekka J Enberg wrote: >> diff --git a/init/main.c b/init/main.c >> index 33ce929..fb0e004 100644 >> --- a/init/main.c >> +++ b/init/main.c >> @@ -576,6 +576,22 @@ asmlinkage void __init start_kernel(void) >> setup_nr_cpu_ids(); >> smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */ >> >> + build_all_zonelists(); >> + page_alloc_init(); >> + >> + printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line); >> + parse_early_param(); >> + parse_args("Booting kernel", static_command_line, __start___param, >> + __stop___param - __start___param, >> + &unknown_bootoption); >> + pidhash_init(); >> + vmalloc_init(); >> + vfs_caches_init_early(); >> + /* >> + * Set up kernel memory allocators >> + */ >> + mem_init(); >> + kmem_cache_init(); > > So what strikes me is a question: > > - why do we want to do pidhash_init and vfs_caches_init_early() so early? > > Yes, pidhash_init() now uses alloc_bootmem. It's an allocation that is not > trivially small, but it's not humongous either (max 4096 hash list heads, > one pointer each).
I can certainly fix that up to use kmalloc() or vmalloc(). I moved it because I wasn't sure how much it's actually allocating and wanted to do the conservative thing here.
Linus Torvalds wrote: > And vfs_caches_init_early() is actually doing some rather strange things, > like doing a "alloc_large_system_hash()" but not unconditionally: it does > it in the "late" initialization too, if not done early. inode_init_early > does soemthing very similar (ie a _conditional_ early init). > > So none of this seems to really get a huge advantage from the early init. > There seems to be some subtle NUMA issues, but do we really want that? I > get the feeling that nobody ever wanted to do it early, and then the NUMA > people said "I don't wnt to do this early, but I don't want to touch the > non-NUMA case, so I'll do it early for non-numa, and late for numa".
SLUB does sysfs setup in kmem_cache_init() and if I saw some oopses if I don't call vfs_caches_init_early() first. I didn't look too closely, though.
Linus Torvalds wrote: > I'm also not entirely sure we really need to do vmalloc_init() that early, > but I dunno. It also uses alloc_bootmem().
We can do that later but then we need to fix up vmalloc_init(). There's actually a patch floating around to do that.
Pekka
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