1991/0723/ss/bbmalloc.c (diff list | history)

ss/bbmalloc.c on 1991/0723
1991/0723		#include "u.h" #include "lib.h" #include "mem.h" #include "dat.h" #include "fns.h" #include "io.h" /* * Allocate memory for use in kernel bitblts. * The allocated memory must have a flushed instruction * cache, and the data cache must be flushed by bbdflush(). * To avoid the need for frequent cache flushes, the memory * is allocated out of an arena, and the i-cache is only * flushed when it has to be reused. By returning an * address in non-cached space, the need for flushing the * d-cache is avoided. * * Currently, the only kernel users of bitblt are devbit, * print, and the cursor stuff in devbit. The cursor * can get drawn at clock interrupt time, so it might need * to bbmalloc while another bitblt is going on. * * This code will have to be interlocked if we ever get * a multiprocessor with a bitmapped display. */ /* a 0->3 bitblt can take 900 words */ enum { nbbarena=8192 /* number of words in an arena */ }; static ulong bbarena[nbbarena]; static ulong *bbcur = bbarena; static ulong *bblast = 0; void * bbmalloc(int nbytes) { int nw; int s; ulong *ans; nw = nbytes/sizeof(long); s = splhi(); if(bbcur + nw > &bbarena[nbbarena]) ans = bbarena; else ans = bbcur; bbcur = ans + nw; splx(s); /* if(ans == bbarena) icflush(ans, sizeof(bbarena)); */ bblast = ans; ans = (void *)ans; return ans; } void bbfree(void *p, int n) { ulong *up; if(p == bblast) bbcur = (ulong *)(((char *)bblast) + n); } void * bbdflush(void *p, int n) { return p; }