[PATCH 20/21] mm: a process flags to avoid blocking allocations

Peter Zijlstra
2006-09-06T13:16:50Z

[-- Attachment #1: pf_mem_nowait.patch --]
[-- Type: text/plain, Size: 1816 bytes --]

PF_MEM_NOWAIT - will make allocations fail before blocking. This is usefull
to convert process behaviour to non-blocking.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Mike Christie <michaelc@cs.wisc.edu>
---
include/linux/sched.h | 1 +
mm/page_alloc.c | 4 ++--
2 files changed, 3 insertions(+), 2 deletions(-)

Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -1056,6 +1056,7 @@ static inline void put_task_struct(struc
#define PF_SPREAD_SLAB 0x02000000 /* Spread some slab caches over cpuset */
#define PF_MEMPOLICY 0x10000000 /* Non-default NUMA mempolicy */
#define PF_MUTEX_TESTER 0x20000000 /* Thread belongs to the rt mutex tester */
+#define PF_MEM_NOWAIT 0x40000000 /* Make allocations fail instead of block */

/*
* Only the _current_ task can read/write to tsk->flags, but other
Index: linux-2.6/mm/page_alloc.c
===================================================================
--- linux-2.6.orig/mm/page_alloc.c
+++ linux-2.6/mm/page_alloc.c
@@ -912,11 +912,11 @@ struct page * fastcall
__alloc_pages(gfp_t gfp_mask, unsigned int order,
struct zonelist *zonelist)
{
- const gfp_t wait = gfp_mask & __GFP_WAIT;
+ struct task_struct *p = current;
+ const int wait = (gfp_mask & __GFP_WAIT) && !(p->flags & PF_MEM_NOWAIT);
struct zone **z;
struct page *page;
struct reclaim_state reclaim_state;
- struct task_struct *p = current;
int do_retry;
int alloc_flags;
int did_some_progress;