From bae5df8cbb88dd3a3930f1c4f5281e1782961a36 Mon Sep 17 00:00:00 2001 From: kib Date: Tue, 1 Sep 2009 11:41:51 +0000 Subject: Reintroduce the r196640, after fixing the problem with my testing. Remove the altkstacks, instead instantiate threads with kernel stack allocated with the right size from the start. For the thread that has kernel stack cached, verify that requested stack size is equial to the actual, and reallocate the stack if sizes differ [1]. This fixes the bug introduced by r173361 that was committed several days after r173004 and consisted of kthread_add(9) ignoring the non-default kernel stack size. Also, r173361 removed the caching of the kernel stacks for a non-first thread in the process. Introduce separate kernel stack cache that keeps some limited amount of preallocated kernel stacks to lower the latency of thread allocation. Add vm_lowmem handler to prune the cache on low memory condition. This way, system with reasonable amount of the threads get lower latency of thread creation, while still not exhausting significant portion of KVA for unused kstacks. Submitted by: peter [1] Discussed with: jhb, julian, peter Reviewed by: jhb Tested by: pho (and retested according to new test scenarious) MFC after: 1 week --- sys/kern/kern_fork.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) (limited to 'sys/kern/kern_fork.c') diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c index 4e2eaa9..03d8cbc 100644 --- a/sys/kern/kern_fork.c +++ b/sys/kern/kern_fork.c @@ -39,6 +39,7 @@ __FBSDID("$FreeBSD$"); #include "opt_kdtrace.h" #include "opt_ktrace.h" +#include "opt_kstack_pages.h" #include #include @@ -276,25 +277,29 @@ norfproc_fail: mem_charged = 0; vm2 = NULL; + if (pages == 0) + pages = KSTACK_PAGES; /* Allocate new proc. */ newproc = uma_zalloc(proc_zone, M_WAITOK); - if (TAILQ_EMPTY(&newproc->p_threads)) { - td2 = thread_alloc(); + td2 = FIRST_THREAD_IN_PROC(newproc); + if (td2 == NULL) { + td2 = thread_alloc(pages); if (td2 == NULL) { error = ENOMEM; goto fail1; } proc_linkup(newproc, td2); - } else - td2 = FIRST_THREAD_IN_PROC(newproc); - - /* Allocate and switch to an alternate kstack if specified. */ - if (pages != 0) { - if (!vm_thread_new_altkstack(td2, pages)) { - error = ENOMEM; - goto fail1; + } else { + if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { + if (td2->td_kstack != 0) + vm_thread_dispose(td2); + if (!thread_alloc_stack(td2, pages)) { + error = ENOMEM; + goto fail1; + } } } + if ((flags & RFMEM) == 0) { vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); if (vm2 == NULL) { -- cgit v1.1