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Message-Id: <20110111135547.ce6c273c.akpm@linux-foundation.org>
Date: Tue, 11 Jan 2011 13:55:47 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: David Rientjes <rientjes@...gle.com>
Cc: linux-kernel@...r.kernel.org, hughd@...gle.com, mel@....ul.ie
Subject: Re: +
mm-vmscan-reclaim-order-0-and-use-compaction-instead-of-lumpy-reclaim-avoid-a-potential-deadlock-due-to-lock_page-during-direct-compaction-fix.patch
added to -mm tree
On Tue, 11 Jan 2011 13:43:06 -0800 (PST)
David Rientjes <rientjes@...gle.com> wrote:
> On Tue, 11 Jan 2011, akpm@...ux-foundation.org wrote:
>
> > diff -puN mm/page_alloc.c~mm-vmscan-reclaim-order-0-and-use-compaction-instead-of-lumpy-reclaim-avoid-a-potential-deadlock-due-to-lock_page-during-direct-compaction-fix mm/page_alloc.c
> > --- a/mm/page_alloc.c~mm-vmscan-reclaim-order-0-and-use-compaction-instead-of-lumpy-reclaim-avoid-a-potential-deadlock-due-to-lock_page-during-direct-compaction-fix
> > +++ a/mm/page_alloc.c
> > @@ -1815,15 +1815,15 @@ __alloc_pages_direct_compact(gfp_t gfp_m
> > int migratetype, unsigned long *did_some_progress)
> > {
> > struct page *page;
> > - struct task_struct *p = current;
> > + struct task_struct *tsk = current;
> >
> > if (!order || compaction_deferred(preferred_zone))
> > return NULL;
> >
> > - p->flags |= PF_MEMALLOC;
> > + tsk->flags |= PF_MEMALLOC;
> > *did_some_progress = try_to_compact_pages(zonelist, order, gfp_mask,
> > nodemask);
> > - p->flags &= ~PF_MEMALLOC;
> > + tsk->flags &= ~PF_MEMALLOC;
> > if (*did_some_progress != COMPACT_SKIPPED) {
> >
> > /* Page migration frees to the PCP lists but we want merging */
>
> This could be done for all of the page allocator functions in
> mm/page_alloc.c, I think it would be inconsistent and slightly harder to
> read if it were done in only one.
Using "p" for any identifier which has less-than-teeny scope is plain
dumb. It's meaningless and useless.
Anyway...
Subject: mm/page_alloc.c: don't cache `current' in a local
From: Andrew Morton <akpm@...ux-foundation.org>
It's old-fashioned and unneeded.
akpm:/usr/src/25> size mm/page_alloc.o
text data bss dec hex filename
39884 1241317 18808 1300009 13d629 mm/page_alloc.o (before)
39838 1241317 18808 1299963 13d5fb mm/page_alloc.o (after)
Cc: David Rientjes <rientjes@...gle.com>
Cc: Mel Gorman <mel@....ul.ie>
Cc: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---
mm/page_alloc.c | 24 ++++++++++--------------
1 file changed, 10 insertions(+), 14 deletions(-)
diff -puN mm/page_alloc.c~mm-page_allocc-dont-cache-current-in-a-local mm/page_alloc.c
--- a/mm/page_alloc.c~mm-page_allocc-dont-cache-current-in-a-local
+++ a/mm/page_alloc.c
@@ -1809,15 +1809,14 @@ __alloc_pages_direct_compact(gfp_t gfp_m
bool sync_migration)
{
struct page *page;
- struct task_struct *tsk = current;
if (!order || compaction_deferred(preferred_zone))
return NULL;
- tsk->flags |= PF_MEMALLOC;
+ current->flags |= PF_MEMALLOC;
*did_some_progress = try_to_compact_pages(zonelist, order, gfp_mask,
nodemask, sync_migration);
- tsk->flags &= ~PF_MEMALLOC;
+ current->flags &= ~PF_MEMALLOC;
if (*did_some_progress != COMPACT_SKIPPED) {
/* Page migration frees to the PCP lists but we want merging */
@@ -1869,23 +1868,22 @@ __alloc_pages_direct_reclaim(gfp_t gfp_m
{
struct page *page = NULL;
struct reclaim_state reclaim_state;
- struct task_struct *p = current;
bool drained = false;
cond_resched();
/* We now go into synchronous reclaim */
cpuset_memory_pressure_bump();
- p->flags |= PF_MEMALLOC;
+ current->flags |= PF_MEMALLOC;
lockdep_set_current_reclaim_state(gfp_mask);
reclaim_state.reclaimed_slab = 0;
- p->reclaim_state = &reclaim_state;
+ current->reclaim_state = &reclaim_state;
*did_some_progress = try_to_free_pages(zonelist, order, gfp_mask, nodemask);
- p->reclaim_state = NULL;
+ current->reclaim_state = NULL;
lockdep_clear_current_reclaim_state();
- p->flags &= ~PF_MEMALLOC;
+ current->flags &= ~PF_MEMALLOC;
cond_resched();
@@ -1950,7 +1948,6 @@ void wake_all_kswapd(unsigned int order,
static inline int
gfp_to_alloc_flags(gfp_t gfp_mask)
{
- struct task_struct *p = current;
int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;
const gfp_t wait = gfp_mask & __GFP_WAIT;
@@ -1977,12 +1974,12 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
* See also cpuset_zone_allowed() comment in kernel/cpuset.c.
*/
alloc_flags &= ~ALLOC_CPUSET;
- } else if (unlikely(rt_task(p)) && !in_interrupt())
+ } else if (unlikely(rt_task(current)) && !in_interrupt())
alloc_flags |= ALLOC_HARDER;
if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {
if (!in_interrupt() &&
- ((p->flags & PF_MEMALLOC) ||
+ ((current->flags & PF_MEMALLOC) ||
unlikely(test_thread_flag(TIF_MEMDIE))))
alloc_flags |= ALLOC_NO_WATERMARKS;
}
@@ -2001,7 +1998,6 @@ __alloc_pages_slowpath(gfp_t gfp_mask, u
int alloc_flags;
unsigned long pages_reclaimed = 0;
unsigned long did_some_progress;
- struct task_struct *p = current;
bool sync_migration = false;
/*
@@ -2060,7 +2056,7 @@ rebalance:
goto nopage;
/* Avoid recursion of direct reclaim */
- if (p->flags & PF_MEMALLOC)
+ if (current->flags & PF_MEMALLOC)
goto nopage;
/* Avoid allocations with no watermarks from looping endlessly */
@@ -2153,7 +2149,7 @@ nopage:
if (!(gfp_mask & __GFP_NOWARN) && printk_ratelimit()) {
printk(KERN_WARNING "%s: page allocation failure."
" order:%d, mode:0x%x\n",
- p->comm, order, gfp_mask);
+ current->comm, order, gfp_mask);
dump_stack();
show_mem();
}
_
--
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