VM: simplify slab allocator
. only keep a list of non-empty, non-full pages with slab objects . simplifies alloc/free operations and reduces list management overhead
This commit is contained in:
Ben Gras
parent
19e6dad47b
commit
0d1f2e6be2
3 changed files with 80 additions and 132 deletions
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@ -185,11 +185,9 @@ static u32_t findhole(void)
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/*===========================================================================*
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* vm_freepages *
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*===========================================================================*/
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static void vm_freepages(vir_bytes vir, vir_bytes phys, int pages, int reason)
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void vm_freepages(vir_bytes vir, int pages)
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{
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assert(reason >= 0 && reason < VMP_CATEGORIES);
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assert(!(vir % I386_PAGE_SIZE));
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assert(!(phys % I386_PAGE_SIZE));
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extern char _end;
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if(vir < (vir_bytes) &_end) {
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@ -197,9 +195,9 @@ static void vm_freepages(vir_bytes vir, vir_bytes phys, int pages, int reason)
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return;
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}
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free_mem(ABS2CLICK(phys), pages);
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if(pt_writemap(vmprocess, &vmprocess->vm_pt, vir,
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MAP_NONE, pages*I386_PAGE_SIZE, 0, WMF_OVERWRITE) != OK)
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MAP_NONE, pages*I386_PAGE_SIZE, 0,
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WMF_OVERWRITE | WMF_FREE) != OK)
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panic("vm_freepages: pt_writemap failed");
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#if SANITYCHECKS
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@ -1080,8 +1078,7 @@ void pt_free(pt_t *pt)
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for(i = 0; i < I386_VM_DIR_ENTRIES; i++)
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if(pt->pt_pt[i])
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vm_freepages((vir_bytes) pt->pt_pt[i],
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I386_VM_PFA(pt->pt_dir[i]), 1, VMP_PAGETABLE);
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vm_freepages((vir_bytes) pt->pt_pt[i], 1);
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return;
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}
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@ -82,6 +82,7 @@ int handle_memory(struct vmproc *vmp, vir_bytes mem, vir_bytes len, int
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/* $(ARCH)/pagetable.c */
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void pt_init();
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void vm_freepages(vir_bytes vir, int pages);
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void pt_init_mem(void);
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void pt_check(struct vmproc *vmp);
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int pt_new(pt_t *pt);
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@ -23,6 +23,8 @@
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#include <memory.h>
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#include <sys/param.h>
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#include "glo.h"
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#include "proto.h"
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#include "util.h"
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@ -72,6 +74,8 @@
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#define SETBIT(f, b) {OFF(f,b); SLABDATAUSE(f, BITEL(f,b)|= BITPAT(b); (f)->sdh.nused++;); }
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#define CLEARBIT(f, b) {ON(f, b); SLABDATAUSE(f, BITEL(f,b)&=~BITPAT(b); (f)->sdh.nused--; (f)->sdh.freeguess = (b);); }
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#define OBJALIGN 8
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#define MINSIZE 8
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#define MAXSIZE (SLABSIZES-1+MINSIZE)
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#define USEELEMENTS (1+(VM_PAGE_SIZE/MINSIZE/8))
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@ -97,8 +101,6 @@ struct sdh {
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#if SANITYCHECKS
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u32_t magic1;
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#endif
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u8_t list;
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u16_t nused; /* Number of data items used in this slab. */
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int freeguess;
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struct slabdata *next, *prev;
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elements_t usebits;
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@ -107,6 +109,7 @@ struct sdh {
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int writable; /* data item number or WRITABLE_* */
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u32_t magic2;
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#endif
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u16_t nused; /* Number of data items used in this slab. */
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};
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#define DATABYTES (VM_PAGE_SIZE-sizeof(struct sdh))
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@ -116,17 +119,11 @@ struct sdh {
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#define JUNK 0xdeadbeef
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#define NOJUNK 0xc0ffee
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#define LIST_UNUSED 0
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#define LIST_FREE 1
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#define LIST_USED 2
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#define LIST_FULL 3
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#define LIST_NUMBER 4
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static struct slabheader {
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struct slabdata {
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struct sdh sdh;
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u8_t data[DATABYTES];
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} *list_head[LIST_NUMBER];
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struct sdh sdh;
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} *list_head;
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} slabs[SLABSIZES];
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static int objstats(void *, int, struct slabheader **, struct slabdata
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@ -141,32 +138,12 @@ static int objstats(void *, int, struct slabheader **, struct slabdata
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s = &slabs[i]; \
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}
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#define LH(sl, l) (sl)->list_head[l]
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/* move head of list l1 to list of l2 in slabheader sl. */
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#define MOVEHEAD(sl, l1, l2) { \
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struct slabdata *t; \
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assert(LH(sl,l1)); \
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REMOVEHEAD(sl, l1, t); \
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ADDHEAD(t, sl, l2); \
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}
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/* remove head of list 'list' in sl, assign it unlinked to 'to'. */
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#define REMOVEHEAD(sl, list, to) { \
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struct slabdata *dat; \
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dat = (to) = LH(sl, list); \
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assert(dat); \
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LH(sl, list) = dat->sdh.next; \
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UNLINKNODE(dat); \
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}
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/* move slabdata nw to slabheader sl under list number l. */
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#define ADDHEAD(nw, sl, l) { \
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#define ADDHEAD(nw, sl) { \
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SLABDATAUSE(nw, \
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(nw)->sdh.next = LH(sl, l); \
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(nw)->sdh.prev = NULL; \
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(nw)->sdh.list = l;); \
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LH(sl, l) = (nw); \
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(nw)->sdh.next = sl->list_head; \
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(nw)->sdh.prev = NULL;); \
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sl->list_head = nw; \
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if((nw)->sdh.next) { \
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SLABDATAUSE((nw)->sdh.next, \
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(nw)->sdh.next->sdh.prev = (nw);); \
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@ -181,7 +158,7 @@ static int objstats(void *, int, struct slabheader **, struct slabdata
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if(next) { SLABDATAUSE(next, next->sdh.prev = prev;); } \
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}
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struct slabdata *newslabdata(int list)
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static struct slabdata *newslabdata()
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{
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struct slabdata *n;
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phys_bytes p;
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@ -202,7 +179,6 @@ struct slabdata *newslabdata(int list)
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#endif
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n->sdh.nused = 0;
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n->sdh.freeguess = 0;
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n->sdh.list = list;
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#if SANITYCHECKS
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n->sdh.writable = WRITABLE_HEADER;
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@ -218,9 +194,9 @@ struct slabdata *newslabdata(int list)
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* checklist *
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*===========================================================================*/
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static int checklist(char *file, int line,
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struct slabheader *s, int l, int bytes)
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struct slabheader *s, int bytes)
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{
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struct slabdata *n = s->list_head[l];
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struct slabdata *n = s->list_head;
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int ch = 0;
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while(n) {
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@ -258,9 +234,7 @@ void slab_sanitycheck(char *file, int line)
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int s;
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for(s = 0; s < SLABSIZES; s++) {
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int l;
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for(l = 0; l < LIST_NUMBER; l++) {
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checklist(file, line, &slabs[s], l, s + MINSIZE);
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}
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checklist(file, line, &slabs[s], s + MINSIZE);
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}
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}
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@ -289,7 +263,10 @@ void *slaballoc(int bytes)
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int i;
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int count = 0;
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struct slabheader *s;
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struct slabdata *firstused;
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struct slabdata *newslab;
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char *ret;
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bytes = roundup(bytes, OBJALIGN);
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SLABSANITYCHECK(SCL_FUNCTIONS);
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@ -297,53 +274,42 @@ void *slaballoc(int bytes)
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GETSLAB(bytes, s);
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assert(s);
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/* To make the common case more common, make space in the 'used'
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* queue first.
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*/
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if(!LH(s, LIST_USED)) {
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if(!(newslab = s->list_head)) {
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/* Make sure there is something on the freelist. */
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SLABSANITYCHECK(SCL_DETAIL);
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if(!LH(s, LIST_FREE)) {
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struct slabdata *nd = newslabdata(LIST_FREE);
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SLABSANITYCHECK(SCL_DETAIL);
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if(!nd) return NULL;
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ADDHEAD(nd, s, LIST_FREE);
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SLABSANITYCHECK(SCL_DETAIL);
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}
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newslab = newslabdata();
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if(!newslab) return NULL;
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ADDHEAD(newslab, s);
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assert(newslab->sdh.nused == 0);
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} else assert(newslab->sdh.nused > 0);
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assert(newslab->sdh.nused < ITEMSPERPAGE(bytes));
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SLABSANITYCHECK(SCL_DETAIL);
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MOVEHEAD(s, LIST_FREE, LIST_USED);
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SLABSANITYCHECK(SCL_DETAIL);
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}
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SLABSANITYCHECK(SCL_DETAIL);
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assert(s);
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firstused = LH(s, LIST_USED);
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assert(firstused);
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#if SANITYCHECKS
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assert(firstused->sdh.magic1 == MAGIC1);
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assert(firstused->sdh.magic2 == MAGIC2);
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assert(newslab->sdh.magic1 == MAGIC1);
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assert(newslab->sdh.magic2 == MAGIC2);
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#endif
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assert(firstused->sdh.nused < ITEMSPERPAGE(bytes));
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for(i = firstused->sdh.freeguess;
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for(i = newslab->sdh.freeguess;
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count < ITEMSPERPAGE(bytes); count++, i++) {
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SLABSANITYCHECK(SCL_DETAIL);
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i = i % ITEMSPERPAGE(bytes);
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if(!GETBIT(firstused, i)) {
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char *ret;
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SETBIT(firstused, i);
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SLABSANITYCHECK(SCL_DETAIL);
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if(firstused->sdh.nused == ITEMSPERPAGE(bytes)) {
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SLABSANITYCHECK(SCL_DETAIL);
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MOVEHEAD(s, LIST_USED, LIST_FULL);
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SLABSANITYCHECK(SCL_DETAIL);
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if(!GETBIT(newslab, i))
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break;
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}
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SLABSANITYCHECK(SCL_DETAIL);
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ret = ((char *) firstused->data) + i*bytes;
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SLABSANITYCHECK(SCL_FUNCTIONS);
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assert(count < ITEMSPERPAGE(bytes));
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assert(i >= 0 && i < ITEMSPERPAGE(bytes));
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SETBIT(newslab, i);
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if(newslab->sdh.nused == ITEMSPERPAGE(bytes)) {
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UNLINKNODE(newslab);
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s->list_head = newslab->sdh.next;
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}
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ret = ((char *) newslab) + i*bytes;
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#if SANITYCHECKS
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#if MEMPROTECT
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@ -358,31 +324,22 @@ void *slaballoc(int bytes)
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#endif
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#endif
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SLABSANITYCHECK(SCL_FUNCTIONS);
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SLABDATAUSE(firstused, firstused->sdh.freeguess = i+1;);
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SLABDATAUSE(newslab, newslab->sdh.freeguess = i+1;);
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#if SANITYCHECKS
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if(bytes >= SLABSIZES+MINSIZE) {
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printf("slaballoc: odd, bytes %d?\n", bytes);
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}
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if(!slabsane_f(__FILE__, __LINE__, ret, bytes))
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panic("slaballoc: slabsane failed");
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#endif
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assert(!((vir_bytes) ret % OBJALIGN));
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return ret;
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}
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SLABSANITYCHECK(SCL_DETAIL);
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}
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SLABSANITYCHECK(SCL_FUNCTIONS);
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panic("slaballoc: no space in 'used' slabdata");
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/* Not reached. */
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return NULL;
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}
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/*===========================================================================*
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* int objstats *
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*===========================================================================*/
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@ -404,6 +361,8 @@ static inline int objstats(void *mem, int bytes,
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struct slabdata *f;
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int i;
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assert(!(bytes % OBJALIGN));
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OBJSTATSCHECK((char *) mem >= (char *) VM_PAGE_SIZE);
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#if SANITYCHECKS
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@ -422,7 +381,6 @@ static inline int objstats(void *mem, int bytes,
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OBJSTATSCHECK(f->sdh.magic1 == MAGIC1);
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OBJSTATSCHECK(f->sdh.magic2 == MAGIC2);
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#endif
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OBJSTATSCHECK(f->sdh.list == LIST_USED || f->sdh.list == LIST_FULL);
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/* Make sure it's in range. */
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OBJSTATSCHECK((char *) mem >= (char *) f->data);
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@ -453,6 +411,8 @@ void slabfree(void *mem, int bytes)
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struct slabheader *s;
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struct slabdata *f;
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bytes = roundup(bytes, OBJALIGN);
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SLABSANITYCHECK(SCL_FUNCTIONS);
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if(objstats(mem, bytes, &s, &f, &i) != OK) {
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@ -486,24 +446,12 @@ void slabfree(void *mem, int bytes)
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/* Check if this slab changes lists. */
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if(f->sdh.nused == 0) {
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/* Now become FREE; must've been USED */
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assert(f->sdh.list == LIST_USED);
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UNLINKNODE(f);
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if(f == LH(s, LIST_USED))
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LH(s, LIST_USED) = f->sdh.next;
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ADDHEAD(f, s, LIST_FREE);
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if(f == s->list_head) s->list_head = f->sdh.next;
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vm_freepages((vir_bytes) f, 1);
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SLABSANITYCHECK(SCL_DETAIL);
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} else if(f->sdh.nused == ITEMSPERPAGE(bytes)-1) {
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/* Now become USED; must've been FULL */
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assert(f->sdh.list == LIST_FULL);
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UNLINKNODE(f);
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if(f == LH(s, LIST_FULL))
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LH(s, LIST_FULL) = f->sdh.next;
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ADDHEAD(f, s, LIST_USED);
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SLABSANITYCHECK(SCL_DETAIL);
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} else {
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/* Stay USED */
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assert(f->sdh.list == LIST_USED);
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ADDHEAD(f, s);
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}
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SLABSANITYCHECK(SCL_FUNCTIONS);
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@ -520,6 +468,8 @@ void slablock(void *mem, int bytes)
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struct slabheader *s;
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struct slabdata *f;
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bytes = roundup(bytes, OBJALIGN);
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if(objstats(mem, bytes, &s, &f, &i) != OK)
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panic("slablock objstats failed");
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@ -537,6 +487,8 @@ void slabunlock(void *mem, int bytes)
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struct slabheader *s;
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struct slabdata *f;
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bytes = roundup(bytes, OBJALIGN);
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if(objstats(mem, bytes, &s, &f, &i) != OK)
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panic("slabunlock objstats failed");
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@ -557,10 +509,9 @@ void slabstats(void)
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if(n%1000) return;
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for(s = 0; s < SLABSIZES; s++) {
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int l;
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for(l = 0; l < LIST_NUMBER; l++) {
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int b, t;
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b = s + MINSIZE;
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t = checklist(__FILE__, __LINE__, &slabs[s], l, b);
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t = checklist(__FILE__, __LINE__, &slabs[s], b);
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if(t > 0) {
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int bytes = t * b;
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@ -568,7 +519,6 @@ void slabstats(void)
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totalbytes += bytes;
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}
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}
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}
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if(pages > 0) {
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printf("VMSTATS: %dK net used in slab objects in %d pages (%dkB): %d%% utilization\n",
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