nexoniarz/SchOS
nexoniarz/SchOS
Watch
1
0
Fork
You've already forked SchOS
 0
Code Issues Pull requests Projects Releases 1 Packages Wiki Activity Actions

kalloc: never-used memory stays a range; 256 GB; free is a counter

Browse source 
Every page of RAM went onto the free list at boot, which means writing
each one -- a link, and kfree()'s 4 KB of junk -- before the first
process ran: 64 GB of memset on a 64 GB machine to say it was free.
Memory nobody has used yet is kept as a cursor and an end per region
now, and kalloc() takes from those once the list of given-back pages
is empty. A page is first touched by whoever asked for it.

That makes the cap on RAM cheap to raise, and PHYSTOP_MAX goes from 64
to 256 GB, which still leaves 248 GB of the kernel PDPT for device
windows. MEMREGION_MAX goes from 32 to 64 for the firmware maps that
cut RAM into many pieces.

kalloc_free_bytes() walked the whole free list under the allocator's
lock -- two million links on 8 GB, every second top or fastfetch was
running, with every CPU that wanted a page waiting behind it. It reads
a counter now. And the buffer cache, which keeps what it grows to, is
reported as Buffers in /proc/meminfo and sysinfo(2) rather than as
memory used by nothing.

Checked under QEMU at 1, 2 and 6 GB: MemFree right, zsh splitting
200000 words, fork loops, a 74 MB write.

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 14:05:40 +02:00
commit b70e36e0a2
4 changed files with 106 additions and 23 deletions
Download patch file Download diff file Expand all files Collapse all files

6
kernel/dev/procfs.c
View file

@ -88,7 +88,11 @@ gen_meminfo(struct sbuf *sb)
sb_kv(sb, "MemTotal: ", total, "kB");
sb_kv(sb, "MemFree: ", freek, "kB");
sb_kv(sb, "MemAvailable: ", freek, "kB");
sb_kv(sb, "Buffers: ", 0, "kB");
// The buffer cache, which grows to 1/32 of RAM and keeps it: without this
// line that showed up in free(1) as memory "used" by nothing.
uint nbuf, maxbuf;
bcache_size(&nbuf, &maxbuf);
sb_kv(sb, "Buffers: ", (uint64)nbuf * (BSIZE / 1024), "kB");
sb_kv(sb, "Cached: ", 0, "kB");
sb_kv(sb, "SwapTotal: ", 0, "kB");
sb_kv(sb, "SwapFree: ", 0, "kB");