Re: [PATCH 09/12] mm: remove throttle_vm_writeback
On Thu, 2007-04-05 at 15:44 -0700, Andrew Morton wrote:
> On Thu, 05 Apr 2007 19:42:18 +0200
> [EMAIL PROTECTED] wrote:
>
> > rely on accurate dirty page accounting to provide enough push back
>
> I think we'd like to see a bit more justification than that, please.
it should read like this:
for ( ; ; ) {
get_dirty_limits(_thresh, _thresh, NULL, NULL);
/*
* Boost the allowable dirty threshold a bit for page
* allocators so they don't get DoS'ed by heavy writers
*/
dirty_thresh += dirty_thresh / 10; /* wh... */
if (global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS) +
global_page_state(NR_WRITEBACK) <= dirty_thresh)
break;
congestion_wait(WRITE, HZ/10);
}
[ note the extra NR_FILE_DIRTY ]
now, balance_dirty_pages() is there to ensure:
nr_dirty + nr_unstable + nr_writeback < dirty_thresh (1)
reclaim will (with the introduction of dirty page tracking) never
generate dirty pages, so the only disturbance of that equation is an
increase in nr_writeback.
[ pageout() sets wbc.for_reclaim=1, so NFS traffic will not generate
unstable pages ]
So, what throttle_vm_writeout() does is limit the number of added
writeback pages to 10% of the total limit.
pageout() seems to avoid stuffing pages down a congested bdi
(TODO: has details), along with the much smaller io-queues, the initial
purpose of this function - which was to avoid all memory getting stuck
in io-queues - seems to be handled.
Now the problems...
Trouble is that it currently does not take nr_dirty into account which
in the worst case limits it to 110% of the limit.
Also, I'm seeing (2.6.23-rc8-mm1) live-locks in throttle_vm_writeback()
where nr_dirty + nr_unstable > thresh - which according to (1) should
not happen, and will not change without explicit action.
Hmm maybe the 10% is < nr_cpus * ratelimit_pages.
2 cpus, mem=128M -> ratelimit_pages ~ 512
threshold ~ 1500
so indeed: 150 < 1024.
Still not conclusive but at least getting somewhere.
-
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Re: [PATCH 09/12] mm: remove throttle_vm_writeback
On Thu, 2007-04-05 at 15:44 -0700, Andrew Morton wrote:
On Thu, 05 Apr 2007 19:42:18 +0200
[EMAIL PROTECTED] wrote:
rely on accurate dirty page accounting to provide enough push back
I think we'd like to see a bit more justification than that, please.
it should read like this:
for ( ; ; ) {
get_dirty_limits(background_thresh, dirty_thresh, NULL, NULL);
/*
* Boost the allowable dirty threshold a bit for page
* allocators so they don't get DoS'ed by heavy writers
*/
dirty_thresh += dirty_thresh / 10; /* wh... */
if (global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS) +
global_page_state(NR_WRITEBACK) = dirty_thresh)
break;
congestion_wait(WRITE, HZ/10);
}
[ note the extra NR_FILE_DIRTY ]
now, balance_dirty_pages() is there to ensure:
nr_dirty + nr_unstable + nr_writeback dirty_thresh (1)
reclaim will (with the introduction of dirty page tracking) never
generate dirty pages, so the only disturbance of that equation is an
increase in nr_writeback.
[ pageout() sets wbc.for_reclaim=1, so NFS traffic will not generate
unstable pages ]
So, what throttle_vm_writeout() does is limit the number of added
writeback pages to 10% of the total limit.
pageout() seems to avoid stuffing pages down a congested bdi
(TODO: has details), along with the much smaller io-queues, the initial
purpose of this function - which was to avoid all memory getting stuck
in io-queues - seems to be handled.
Now the problems...
Trouble is that it currently does not take nr_dirty into account which
in the worst case limits it to 110% of the limit.
Also, I'm seeing (2.6.23-rc8-mm1) live-locks in throttle_vm_writeback()
where nr_dirty + nr_unstable thresh - which according to (1) should
not happen, and will not change without explicit action.
Hmm maybe the 10% is nr_cpus * ratelimit_pages.
2 cpus, mem=128M - ratelimit_pages ~ 512
threshold ~ 1500
so indeed: 150 1024.
Still not conclusive but at least getting somewhere.
-
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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 09/12] mm: remove throttle_vm_writeback
On Thu, 05 Apr 2007 19:42:18 +0200 [EMAIL PROTECTED] wrote: > rely on accurate dirty page accounting to provide enough push back I think we'd like to see a bit more justification than that, please. - 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 09/12] mm: remove throttle_vm_writeback
rely on accurate dirty page accounting to provide enough push back
Signed-off-by: Peter Zijlstra <[EMAIL PROTECTED]>
---
Index: linux-2.6-mm/include/linux/writeback.h
===
--- linux-2.6-mm.orig/include/linux/writeback.h 2007-04-05 13:23:51.0
+0200
+++ linux-2.6-mm/include/linux/writeback.h 2007-04-05 13:24:11.0
+0200
@@ -84,7 +84,6 @@ static inline void wait_on_inode(struct
int wakeup_pdflush(long nr_pages);
void laptop_io_completion(void);
void laptop_sync_completion(void);
-void throttle_vm_writeout(gfp_t gfp_mask);
extern struct timer_list laptop_mode_wb_timer;
static inline int laptop_spinned_down(void)
Index: linux-2.6-mm/mm/page-writeback.c
===
--- linux-2.6-mm.orig/mm/page-writeback.c 2007-04-05 13:23:51.0
+0200
+++ linux-2.6-mm/mm/page-writeback.c2007-04-05 13:24:38.0 +0200
@@ -437,37 +437,6 @@ void balance_dirty_pages_ratelimited_nr(
}
EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
-void throttle_vm_writeout(gfp_t gfp_mask)
-{
- long background_thresh;
- long dirty_thresh;
-
- if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) {
- /*
-* The caller might hold locks which can prevent IO completion
-* or progress in the filesystem. So we cannot just sit here
-* waiting for IO to complete.
-*/
- congestion_wait(WRITE, HZ/10);
- return;
- }
-
-for ( ; ; ) {
- get_dirty_limits(_thresh, _thresh, NULL, NULL);
-
-/*
- * Boost the allowable dirty threshold a bit for page
- * allocators so they don't get DoS'ed by heavy writers
- */
-dirty_thresh += dirty_thresh / 10; /* wh... */
-
-if (global_page_state(NR_UNSTABLE_NFS) +
- global_page_state(NR_WRITEBACK) <= dirty_thresh)
- break;
-congestion_wait(WRITE, HZ/10);
-}
-}
-
/*
* writeback at least _min_pages, and keep writing until the amount of dirty
* memory is less than the background threshold, or until we're all clean.
Index: linux-2.6-mm/mm/vmscan.c
===
--- linux-2.6-mm.orig/mm/vmscan.c 2007-04-03 12:17:57.0 +0200
+++ linux-2.6-mm/mm/vmscan.c2007-04-05 13:24:03.0 +0200
@@ -1047,8 +1047,6 @@ static unsigned long shrink_zone(int pri
}
}
- throttle_vm_writeout(sc->gfp_mask);
-
atomic_dec(>reclaim_in_progress);
return nr_reclaimed;
}
--
-
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Re: [PATCH 09/12] mm: remove throttle_vm_writeback
On Thu, 05 Apr 2007 19:42:18 +0200 [EMAIL PROTECTED] wrote: rely on accurate dirty page accounting to provide enough push back I think we'd like to see a bit more justification than that, please. - 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 09/12] mm: remove throttle_vm_writeback
rely on accurate dirty page accounting to provide enough push back
Signed-off-by: Peter Zijlstra [EMAIL PROTECTED]
---
Index: linux-2.6-mm/include/linux/writeback.h
===
--- linux-2.6-mm.orig/include/linux/writeback.h 2007-04-05 13:23:51.0
+0200
+++ linux-2.6-mm/include/linux/writeback.h 2007-04-05 13:24:11.0
+0200
@@ -84,7 +84,6 @@ static inline void wait_on_inode(struct
int wakeup_pdflush(long nr_pages);
void laptop_io_completion(void);
void laptop_sync_completion(void);
-void throttle_vm_writeout(gfp_t gfp_mask);
extern struct timer_list laptop_mode_wb_timer;
static inline int laptop_spinned_down(void)
Index: linux-2.6-mm/mm/page-writeback.c
===
--- linux-2.6-mm.orig/mm/page-writeback.c 2007-04-05 13:23:51.0
+0200
+++ linux-2.6-mm/mm/page-writeback.c2007-04-05 13:24:38.0 +0200
@@ -437,37 +437,6 @@ void balance_dirty_pages_ratelimited_nr(
}
EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
-void throttle_vm_writeout(gfp_t gfp_mask)
-{
- long background_thresh;
- long dirty_thresh;
-
- if ((gfp_mask (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) {
- /*
-* The caller might hold locks which can prevent IO completion
-* or progress in the filesystem. So we cannot just sit here
-* waiting for IO to complete.
-*/
- congestion_wait(WRITE, HZ/10);
- return;
- }
-
-for ( ; ; ) {
- get_dirty_limits(background_thresh, dirty_thresh, NULL, NULL);
-
-/*
- * Boost the allowable dirty threshold a bit for page
- * allocators so they don't get DoS'ed by heavy writers
- */
-dirty_thresh += dirty_thresh / 10; /* wh... */
-
-if (global_page_state(NR_UNSTABLE_NFS) +
- global_page_state(NR_WRITEBACK) = dirty_thresh)
- break;
-congestion_wait(WRITE, HZ/10);
-}
-}
-
/*
* writeback at least _min_pages, and keep writing until the amount of dirty
* memory is less than the background threshold, or until we're all clean.
Index: linux-2.6-mm/mm/vmscan.c
===
--- linux-2.6-mm.orig/mm/vmscan.c 2007-04-03 12:17:57.0 +0200
+++ linux-2.6-mm/mm/vmscan.c2007-04-05 13:24:03.0 +0200
@@ -1047,8 +1047,6 @@ static unsigned long shrink_zone(int pri
}
}
- throttle_vm_writeout(sc-gfp_mask);
-
atomic_dec(zone-reclaim_in_progress);
return nr_reclaimed;
}
--
-
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