Date: Tue, 11 Dec 2018 02:54:36 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r341810 - in head/sys: kern x86/x86 Message-ID: <201812110254.wBB2sa1P047791@repo.freebsd.org>
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Author: kib Date: Tue Dec 11 02:54:36 2018 New Revision: 341810 URL: https://svnweb.freebsd.org/changeset/base/341810 Log: Free bootstacks after AP startup. Bootstacks are unused after APs executed sched_throw() in init_secondary_tail() and started executing on proper idle thread stack. Add sysinit that detects that the idle thread for each CPU was scheduled at least once, and free corresponding bootstack. Slight addition of the code (~200 bytes) is compensated by the saving, because even on typical small modern desktop CPU we leak 128K of memory otherwise (4 pages x 8 threads). Reviewed by: jhb MFC after: 1 week Differential revision: https://reviews.freebsd.org/D18486 Modified: head/sys/kern/kern_thread.c head/sys/x86/x86/mp_x86.c Modified: head/sys/kern/kern_thread.c ============================================================================== --- head/sys/kern/kern_thread.c Tue Dec 11 02:48:49 2018 (r341809) +++ head/sys/kern/kern_thread.c Tue Dec 11 02:54:36 2018 (r341810) @@ -197,7 +197,7 @@ thread_ctor(void *mem, int size, void *arg, int flags) td = (struct thread *)mem; td->td_state = TDS_INACTIVE; - td->td_oncpu = NOCPU; + td->td_lastcpu = td->td_oncpu = NOCPU; td->td_tid = tid_alloc(); Modified: head/sys/x86/x86/mp_x86.c ============================================================================== --- head/sys/x86/x86/mp_x86.c Tue Dec 11 02:48:49 2018 (r341809) +++ head/sys/x86/x86/mp_x86.c Tue Dec 11 02:54:36 2018 (r341810) @@ -1071,9 +1071,23 @@ init_secondary_tail(void) /* NOTREACHED */ } -/******************************************************************* - * local functions and data - */ +static void +smp_after_idle_runnable(void *arg __unused) +{ + struct thread *idle_td; + int cpu; + + for (cpu = 1; cpu < mp_ncpus; cpu++) { + idle_td = pcpu_find(cpu)->pc_idlethread; + while (idle_td->td_lastcpu == NOCPU && + idle_td->td_oncpu == NOCPU) + cpu_spinwait(); + kmem_free((vm_offset_t)bootstacks[cpu], kstack_pages * + PAGE_SIZE); + } +} +SYSINIT(smp_after_idle_runnable, SI_SUB_SMP, SI_ORDER_ANY, + smp_after_idle_runnable, NULL); /* * We tell the I/O APIC code about all the CPUs we want to receive
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