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smp: 64 processors, and say how many there are

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NCPU was 16, under what a desktop has today. 64 costs 48 more TSS
I/O bitmaps and scheduler stacks, about 800 KB of BSS. Past 254 the
APIC would need x2APIC mode, which is a separate change.

With more than 16 there were two other ceilings. sched_getaffinity
wrote "CPU 0" and returned 0, and musl clears every byte past the
count returned -- so the mask came back empty and nproc, make -j and
sysconf(_SC_NPROCESSORS_ONLN) all said 1, on any machine. It returns
the mask of processors that started, and its size, now. And /proc
rendered every file into 2 KB, which /proc/cpuinfo ran out of at the
eighteenth processor without a word; /proc/pci, /proc/interrupts and
/proc/mounts were each one bigger machine from the same cut. There is
one 64 KB buffer for it now behind a sleeplock, since there is no
allocator for contiguous pages, and the generators that write raw
are given the real capacity instead of a constant.

Checked under QEMU with -smp 24: nproc 24, /proc/cpuinfo whole.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
This commit is contained in:
Nexoniarz 2026-10-23 13:50:08 +02:00
commit c1af31f75a
5 changed files with 69 additions and 36 deletions
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2
include/param.h
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@ -25,7 +25,7 @@
#define NPROC 128 // maximum number of processes
#define KSTACKSIZE 8192 // per-process kernel stack; see kstacks[] in proc.c
#define KSTACK_CANARY 0xDEADC0DEDEADC0DEULL // sentinel at kstack[0], see kstack_check_canary()
#define NCPU 16 // maximum number of CPUs
#define NCPU 64 // maximum number of CPUs
#define NOFILE 128 // open files per process
#define NFILE 512 // open files per system
#define NINODE 200 // maximum number of active i-nodes