Re: [PATCH 10/12] mm: page_alloc_wait
On Thu, 2007-04-05 at 15:57 -0700, Andrew Morton wrote: > On Thu, 05 Apr 2007 19:42:19 +0200 > [EMAIL PROTECTED] wrote: > > > Introduce a mechanism to wait on free memory. > > > > Currently congestion_wait() is abused to do this. > > Such a very small explanation for such a terrifying change. Yes, I suck at writing changelogs, bad me. Normally I would take a day to write them, but I just wanted to get this code out there. Perhaps a bad decision. > > ... > > > > --- linux-2.6-mm.orig/mm/vmscan.c 2007-04-05 16:29:46.0 +0200 > > +++ linux-2.6-mm/mm/vmscan.c2007-04-05 16:29:49.0 +0200 > > @@ -1436,6 +1436,7 @@ static int kswapd(void *p) > > finish_wait(>kswapd_wait, ); > > > > balance_pgdat(pgdat, order); > > + page_alloc_ok(); > > } > > return 0; > > } > > For a start, we don't know that kswapd freed pages which are in a suitable > zone. And we don't know that kswapd freed pages which are in a suitable > cpuset. > > congestion_wait() is similarly ignorant of the suitability of the pages, > but the whole idea behind congestion_wait is that it will throttle page > allocators to some speed which is proportional to the speed at which the IO > systems can retire writes - view it as a variable-speed polling operation, > in which the polling frequency goes up when the IO system gets faster. > This patch changes that philosophy fundamentally. That's worth more than a > 2-line changelog. > > Also, there might be situations in which kswapd gets stuck in some dark > corner. Perhaps the process which is waiting in the page allocator holds > filesystem locks which kswapd is blocked on. Or kswapd might be blocked on > a particular request queue, or a dead NFS server or something. The timeout > will save us, but things will be slow. > > There could be other problems too, dunno - this stuff is tricky. Why are > you changing it, what problems are being solved, etc? Lets start with the why, because of 12/12; I wanted to introduce per BDI congestion feedback, and hence needed a BDI context for congestion_wait(). These specific callers weren't in the context of a BDI but of a more global idea. Perhaps I could call page_alloc_ok() from bdi_congestion_end() irrespective of the actual BDI uncongested? That would more or less give the old semantics. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 10/12] mm: page_alloc_wait
On Thu, 2007-04-05 at 15:57 -0700, Andrew Morton wrote: On Thu, 05 Apr 2007 19:42:19 +0200 [EMAIL PROTECTED] wrote: Introduce a mechanism to wait on free memory. Currently congestion_wait() is abused to do this. Such a very small explanation for such a terrifying change. Yes, I suck at writing changelogs, bad me. Normally I would take a day to write them, but I just wanted to get this code out there. Perhaps a bad decision. ... --- linux-2.6-mm.orig/mm/vmscan.c 2007-04-05 16:29:46.0 +0200 +++ linux-2.6-mm/mm/vmscan.c2007-04-05 16:29:49.0 +0200 @@ -1436,6 +1436,7 @@ static int kswapd(void *p) finish_wait(pgdat-kswapd_wait, wait); balance_pgdat(pgdat, order); + page_alloc_ok(); } return 0; } For a start, we don't know that kswapd freed pages which are in a suitable zone. And we don't know that kswapd freed pages which are in a suitable cpuset. congestion_wait() is similarly ignorant of the suitability of the pages, but the whole idea behind congestion_wait is that it will throttle page allocators to some speed which is proportional to the speed at which the IO systems can retire writes - view it as a variable-speed polling operation, in which the polling frequency goes up when the IO system gets faster. This patch changes that philosophy fundamentally. That's worth more than a 2-line changelog. Also, there might be situations in which kswapd gets stuck in some dark corner. Perhaps the process which is waiting in the page allocator holds filesystem locks which kswapd is blocked on. Or kswapd might be blocked on a particular request queue, or a dead NFS server or something. The timeout will save us, but things will be slow. There could be other problems too, dunno - this stuff is tricky. Why are you changing it, what problems are being solved, etc? Lets start with the why, because of 12/12; I wanted to introduce per BDI congestion feedback, and hence needed a BDI context for congestion_wait(). These specific callers weren't in the context of a BDI but of a more global idea. Perhaps I could call page_alloc_ok() from bdi_congestion_end() irrespective of the actual BDI uncongested? That would more or less give the old semantics. - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 10/12] mm: page_alloc_wait
On Thu, 05 Apr 2007 19:42:19 +0200 [EMAIL PROTECTED] wrote: > Introduce a mechanism to wait on free memory. > > Currently congestion_wait() is abused to do this. Such a very small explanation for such a terrifying change. > ... > > --- linux-2.6-mm.orig/mm/vmscan.c 2007-04-05 16:29:46.0 +0200 > +++ linux-2.6-mm/mm/vmscan.c 2007-04-05 16:29:49.0 +0200 > @@ -1436,6 +1436,7 @@ static int kswapd(void *p) > finish_wait(>kswapd_wait, ); > > balance_pgdat(pgdat, order); > + page_alloc_ok(); > } > return 0; > } For a start, we don't know that kswapd freed pages which are in a suitable zone. And we don't know that kswapd freed pages which are in a suitable cpuset. congestion_wait() is similarly ignorant of the suitability of the pages, but the whole idea behind congestion_wait is that it will throttle page allocators to some speed which is proportional to the speed at which the IO systems can retire writes - view it as a variable-speed polling operation, in which the polling frequency goes up when the IO system gets faster. This patch changes that philosophy fundamentally. That's worth more than a 2-line changelog. Also, there might be situations in which kswapd gets stuck in some dark corner. Perhaps the process which is waiting in the page allocator holds filesystem locks which kswapd is blocked on. Or kswapd might be blocked on a particular request queue, or a dead NFS server or something. The timeout will save us, but things will be slow. There could be other problems too, dunno - this stuff is tricky. Why are you changing it, what problems are being solved, etc? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH 10/12] mm: page_alloc_wait
Introduce a mechanism to wait on free memory.
Currently congestion_wait() is abused to do this.
Signed-off-by: Peter Zijlstra <[EMAIL PROTECTED]>
---
arch/i386/lib/usercopy.c |2 +-
fs/xfs/linux-2.6/kmem.c |4 ++--
include/linux/mm.h |3 +++
mm/page_alloc.c | 25 +++--
mm/shmem.c |2 +-
mm/vmscan.c |1 +
6 files changed, 31 insertions(+), 6 deletions(-)
Index: linux-2.6-mm/arch/i386/lib/usercopy.c
===
--- linux-2.6-mm.orig/arch/i386/lib/usercopy.c 2007-04-05 16:24:15.0
+0200
+++ linux-2.6-mm/arch/i386/lib/usercopy.c 2007-04-05 16:29:49.0
+0200
@@ -751,7 +751,7 @@ survive:
if (retval == -ENOMEM && is_init(current)) {
up_read(>mm->mmap_sem);
- congestion_wait(WRITE, HZ/50);
+ page_alloc_wait(HZ/50);
goto survive;
}
Index: linux-2.6-mm/fs/xfs/linux-2.6/kmem.c
===
--- linux-2.6-mm.orig/fs/xfs/linux-2.6/kmem.c 2007-04-05 16:24:15.0
+0200
+++ linux-2.6-mm/fs/xfs/linux-2.6/kmem.c2007-04-05 16:29:49.0
+0200
@@ -53,7 +53,7 @@ kmem_alloc(size_t size, unsigned int __n
printk(KERN_ERR "XFS: possible memory allocation "
"deadlock in %s (mode:0x%x)\n",
__FUNCTION__, lflags);
- congestion_wait(WRITE, HZ/50);
+ page_alloc_wait(HZ/50);
} while (1);
}
@@ -131,7 +131,7 @@ kmem_zone_alloc(kmem_zone_t *zone, unsig
printk(KERN_ERR "XFS: possible memory allocation "
"deadlock in %s (mode:0x%x)\n",
__FUNCTION__, lflags);
- congestion_wait(WRITE, HZ/50);
+ page_alloc_wait(HZ/50);
} while (1);
}
Index: linux-2.6-mm/include/linux/mm.h
===
--- linux-2.6-mm.orig/include/linux/mm.h2007-04-05 16:24:15.0
+0200
+++ linux-2.6-mm/include/linux/mm.h 2007-04-05 16:29:49.0 +0200
@@ -1028,6 +1028,9 @@ extern void setup_per_cpu_pageset(void);
static inline void setup_per_cpu_pageset(void) {}
#endif
+void page_alloc_ok(void);
+long page_alloc_wait(long timeout);
+
/* prio_tree.c */
void vma_prio_tree_add(struct vm_area_struct *, struct vm_area_struct *old);
void vma_prio_tree_insert(struct vm_area_struct *, struct prio_tree_root *);
Index: linux-2.6-mm/mm/page_alloc.c
===
--- linux-2.6-mm.orig/mm/page_alloc.c 2007-04-05 16:24:15.0 +0200
+++ linux-2.6-mm/mm/page_alloc.c2007-04-05 16:35:04.0 +0200
@@ -107,6 +107,9 @@ unsigned long __meminitdata nr_kernel_pa
unsigned long __meminitdata nr_all_pages;
static unsigned long __initdata dma_reserve;
+static wait_queue_head_t page_alloc_wqh =
+ __WAIT_QUEUE_HEAD_INITIALIZER(page_alloc_wqh);
+
#ifdef CONFIG_ARCH_POPULATES_NODE_MAP
/*
* MAX_ACTIVE_REGIONS determines the maxmimum number of distinct
@@ -1698,7 +1701,7 @@ nofail_alloc:
if (page)
goto got_pg;
if (gfp_mask & __GFP_NOFAIL) {
- congestion_wait(WRITE, HZ/50);
+ page_alloc_wait(HZ/50);
goto nofail_alloc;
}
}
@@ -1763,7 +1766,7 @@ nofail_alloc:
do_retry = 1;
}
if (do_retry) {
- congestion_wait(WRITE, HZ/50);
+ page_alloc_wait(HZ/50);
goto rebalance;
}
@@ -4217,3 +4220,21 @@ void set_pageblock_flags_group(struct pa
else
__clear_bit(bitidx + start_bitidx, bitmap);
}
+
+void page_alloc_ok(void)
+{
+ if (waitqueue_active(_alloc_wqh))
+ wake_up(_alloc_wqh);
+}
+
+long page_alloc_wait(long timeout)
+{
+ long ret;
+ DEFINE_WAIT(wait);
+
+ prepare_to_wait(_alloc_wqh, , TASK_UNINTERRUPTIBLE);
+ ret = schedule_timeout(timeout);
+ finish_wait(_alloc_wqh, );
+ return ret;
+}
+EXPORT_SYMBOL(page_alloc_wait);
Index: linux-2.6-mm/mm/shmem.c
===
--- linux-2.6-mm.orig/mm/shmem.c2007-04-05 16:24:15.0 +0200
+++ linux-2.6-mm/mm/shmem.c 2007-04-05 16:30:31.0 +0200
@@ -1216,7 +1216,7 @@ repeat:
page_cache_release(swappage);
if (error == -ENOMEM) {
/* let kswapd refresh zone for
Re: [PATCH 10/12] mm: page_alloc_wait
On Thu, 05 Apr 2007 19:42:19 +0200 [EMAIL PROTECTED] wrote: Introduce a mechanism to wait on free memory. Currently congestion_wait() is abused to do this. Such a very small explanation for such a terrifying change. ... --- linux-2.6-mm.orig/mm/vmscan.c 2007-04-05 16:29:46.0 +0200 +++ linux-2.6-mm/mm/vmscan.c 2007-04-05 16:29:49.0 +0200 @@ -1436,6 +1436,7 @@ static int kswapd(void *p) finish_wait(pgdat-kswapd_wait, wait); balance_pgdat(pgdat, order); + page_alloc_ok(); } return 0; } For a start, we don't know that kswapd freed pages which are in a suitable zone. And we don't know that kswapd freed pages which are in a suitable cpuset. congestion_wait() is similarly ignorant of the suitability of the pages, but the whole idea behind congestion_wait is that it will throttle page allocators to some speed which is proportional to the speed at which the IO systems can retire writes - view it as a variable-speed polling operation, in which the polling frequency goes up when the IO system gets faster. This patch changes that philosophy fundamentally. That's worth more than a 2-line changelog. Also, there might be situations in which kswapd gets stuck in some dark corner. Perhaps the process which is waiting in the page allocator holds filesystem locks which kswapd is blocked on. Or kswapd might be blocked on a particular request queue, or a dead NFS server or something. The timeout will save us, but things will be slow. There could be other problems too, dunno - this stuff is tricky. Why are you changing it, what problems are being solved, etc? - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH 10/12] mm: page_alloc_wait
Introduce a mechanism to wait on free memory.
Currently congestion_wait() is abused to do this.
Signed-off-by: Peter Zijlstra [EMAIL PROTECTED]
---
arch/i386/lib/usercopy.c |2 +-
fs/xfs/linux-2.6/kmem.c |4 ++--
include/linux/mm.h |3 +++
mm/page_alloc.c | 25 +++--
mm/shmem.c |2 +-
mm/vmscan.c |1 +
6 files changed, 31 insertions(+), 6 deletions(-)
Index: linux-2.6-mm/arch/i386/lib/usercopy.c
===
--- linux-2.6-mm.orig/arch/i386/lib/usercopy.c 2007-04-05 16:24:15.0
+0200
+++ linux-2.6-mm/arch/i386/lib/usercopy.c 2007-04-05 16:29:49.0
+0200
@@ -751,7 +751,7 @@ survive:
if (retval == -ENOMEM is_init(current)) {
up_read(current-mm-mmap_sem);
- congestion_wait(WRITE, HZ/50);
+ page_alloc_wait(HZ/50);
goto survive;
}
Index: linux-2.6-mm/fs/xfs/linux-2.6/kmem.c
===
--- linux-2.6-mm.orig/fs/xfs/linux-2.6/kmem.c 2007-04-05 16:24:15.0
+0200
+++ linux-2.6-mm/fs/xfs/linux-2.6/kmem.c2007-04-05 16:29:49.0
+0200
@@ -53,7 +53,7 @@ kmem_alloc(size_t size, unsigned int __n
printk(KERN_ERR XFS: possible memory allocation
deadlock in %s (mode:0x%x)\n,
__FUNCTION__, lflags);
- congestion_wait(WRITE, HZ/50);
+ page_alloc_wait(HZ/50);
} while (1);
}
@@ -131,7 +131,7 @@ kmem_zone_alloc(kmem_zone_t *zone, unsig
printk(KERN_ERR XFS: possible memory allocation
deadlock in %s (mode:0x%x)\n,
__FUNCTION__, lflags);
- congestion_wait(WRITE, HZ/50);
+ page_alloc_wait(HZ/50);
} while (1);
}
Index: linux-2.6-mm/include/linux/mm.h
===
--- linux-2.6-mm.orig/include/linux/mm.h2007-04-05 16:24:15.0
+0200
+++ linux-2.6-mm/include/linux/mm.h 2007-04-05 16:29:49.0 +0200
@@ -1028,6 +1028,9 @@ extern void setup_per_cpu_pageset(void);
static inline void setup_per_cpu_pageset(void) {}
#endif
+void page_alloc_ok(void);
+long page_alloc_wait(long timeout);
+
/* prio_tree.c */
void vma_prio_tree_add(struct vm_area_struct *, struct vm_area_struct *old);
void vma_prio_tree_insert(struct vm_area_struct *, struct prio_tree_root *);
Index: linux-2.6-mm/mm/page_alloc.c
===
--- linux-2.6-mm.orig/mm/page_alloc.c 2007-04-05 16:24:15.0 +0200
+++ linux-2.6-mm/mm/page_alloc.c2007-04-05 16:35:04.0 +0200
@@ -107,6 +107,9 @@ unsigned long __meminitdata nr_kernel_pa
unsigned long __meminitdata nr_all_pages;
static unsigned long __initdata dma_reserve;
+static wait_queue_head_t page_alloc_wqh =
+ __WAIT_QUEUE_HEAD_INITIALIZER(page_alloc_wqh);
+
#ifdef CONFIG_ARCH_POPULATES_NODE_MAP
/*
* MAX_ACTIVE_REGIONS determines the maxmimum number of distinct
@@ -1698,7 +1701,7 @@ nofail_alloc:
if (page)
goto got_pg;
if (gfp_mask __GFP_NOFAIL) {
- congestion_wait(WRITE, HZ/50);
+ page_alloc_wait(HZ/50);
goto nofail_alloc;
}
}
@@ -1763,7 +1766,7 @@ nofail_alloc:
do_retry = 1;
}
if (do_retry) {
- congestion_wait(WRITE, HZ/50);
+ page_alloc_wait(HZ/50);
goto rebalance;
}
@@ -4217,3 +4220,21 @@ void set_pageblock_flags_group(struct pa
else
__clear_bit(bitidx + start_bitidx, bitmap);
}
+
+void page_alloc_ok(void)
+{
+ if (waitqueue_active(page_alloc_wqh))
+ wake_up(page_alloc_wqh);
+}
+
+long page_alloc_wait(long timeout)
+{
+ long ret;
+ DEFINE_WAIT(wait);
+
+ prepare_to_wait(page_alloc_wqh, wait, TASK_UNINTERRUPTIBLE);
+ ret = schedule_timeout(timeout);
+ finish_wait(page_alloc_wqh, wait);
+ return ret;
+}
+EXPORT_SYMBOL(page_alloc_wait);
Index: linux-2.6-mm/mm/shmem.c
===
--- linux-2.6-mm.orig/mm/shmem.c2007-04-05 16:24:15.0 +0200
+++ linux-2.6-mm/mm/shmem.c 2007-04-05 16:30:31.0 +0200
@@ -1216,7 +1216,7 @@ repeat:
page_cache_release(swappage);
if (error == -ENOMEM) {
/* let kswapd refresh
