Date: Sat, 12 Jan 2002 16:03:24 -0500 From: Dan Moschuk <dan@freebsd.org> To: arch@freebsd.org Subject: review request: new malloc flag M_SHORTWAIT Message-ID: <20020112160324.A32256@spirit.jaded.net>
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The following patch adds a new malloc flag M_SHORTWAIT. All this really
does is pass a small timeout (0.5 seconds) to the msleep() call in
the event that no memory is available. It's needed for things like the
md driver that don't want to block until memory is available (but still would
like to wait a short time).
Catching a case where M_SHORTWAIT | M_WAITOK is passed may want to be
added for the sake of adding it.
Comments?
Index: kern/kern_malloc.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/kern_malloc.c,v
retrieving revision 1.93
diff -u -r1.93 kern_malloc.c
--- kern/kern_malloc.c 12 Sep 2001 08:37:44 -0000 1.93
+++ kern/kern_malloc.c 10 Jan 2002 17:25:49 -0000
@@ -133,7 +133,7 @@
register struct kmemusage *kup;
register struct freelist *freep;
long indx, npg, allocsize;
- int s;
+ int s, timo, r;
caddr_t va, cp, savedlist;
#ifdef INVARIANTS
long *end, *lp;
@@ -147,6 +147,7 @@
KASSERT(curthread->td_intr_nesting_level == 0,
("malloc(M_WAITOK) in interrupt context"));
#endif
+ timo = (flags & M_SHORTWAIT) ? (hz / 2) : 0;
indx = BUCKETINDX(size);
kbp = &bucket[indx];
s = splmem();
@@ -159,8 +160,13 @@
}
if (ksp->ks_limblocks < 65535)
ksp->ks_limblocks++;
- msleep((caddr_t)ksp, &malloc_mtx, PSWP+2, type->ks_shortdesc,
- 0);
+ r = msleep((caddr_t)ksp, &malloc_mtx, PSWP+2,
+ type->ks_shortdesc, timo);
+ if (r == EWOULDBLOCK) {
+ splx(s);
+ mtx_unlock(&malloc_mtx);
+ return ((void *) NULL);
+ }
}
ksp->ks_size |= 1 << indx;
#ifdef INVARIANTS
Index: sys/malloc.h
===================================================================
RCS file: /home/ncvs/src/sys/sys/malloc.h,v
retrieving revision 1.54
diff -u -r1.54 malloc.h
--- sys/malloc.h 10 Aug 2001 06:37:04 -0000 1.54
+++ sys/malloc.h 10 Jan 2002 17:26:00 -0000
@@ -46,6 +46,7 @@
#define M_NOWAIT 0x0001 /* do not block */
#define M_USE_RESERVE 0x0002 /* can alloc out of reserve memory */
#define M_ZERO 0x0004 /* bzero the allocation */
+#define M_SHORTWAIT 0x0008 /* wait for 1s */
#define M_MAGIC 877983977 /* time when first defined :-) */
--
Build a man a fire and he'll be warm for a day.
Set a man on fire and he'll be warm for the rest of his life.
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