diff mbox series

[6.1.y] mm/damon/reclaim: fix quota stauts loss due to online tunings

Message ID 20240227051335.168121-1-sj@kernel.org
State New
Headers
Series [6.1.y] mm/damon/reclaim: fix quota stauts loss due to online tunings |

Commit Message

SeongJae Park Feb. 27, 2024, 5:13 a.m. UTC 
  Patch series "mm/damon: fix quota status loss due to online tunings".

DAMON_RECLAIM and DAMON_LRU_SORT is not preserving internal quota status
when applying new user parameters, and hence could cause temporal quota
accuracy degradation.  Fix it by preserving the status.

This patch (of 2):

For online parameters change, DAMON_RECLAIM creates new scheme based on
latest values of the parameters and replaces the old scheme with the new
one.  When creating it, the internal status of the quota of the old
scheme is not preserved.  As a result, charging of the quota starts from
zero after the online tuning.  The data that collected to estimate the
throughput of the scheme's action is also reset, and therefore the
estimation should start from the scratch again.  Because the throughput
estimation is being used to convert the time quota to the effective size
quota, this could result in temporal time quota inaccuracy.  It would be
recovered over time, though.  In short, the quota accuracy could be
temporarily degraded after online parameters update.

Fix the problem by checking the case and copying the internal fields for
the status.

Link: https://lkml.kernel.org/r/20240216194025.9207-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20240216194025.9207-2-sj@kernel.org
Fixes: e035c280f6df ("mm/damon/reclaim: support online inputs update")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>	[5.19+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 1b0ca4e4ff10a2c8402e2cf70132c683e1c772e4)
---
 mm/damon/reclaim.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

Comments

Greg KH Feb. 27, 2024, 9:19 a.m. UTC | #1 
On Mon, Feb 26, 2024 at 09:13:35PM -0800, SeongJae Park wrote:
> Patch series "mm/damon: fix quota status loss due to online tunings".
> 
> DAMON_RECLAIM and DAMON_LRU_SORT is not preserving internal quota status
> when applying new user parameters, and hence could cause temporal quota
> accuracy degradation.  Fix it by preserving the status.
> 
> This patch (of 2):
> 
> For online parameters change, DAMON_RECLAIM creates new scheme based on
> latest values of the parameters and replaces the old scheme with the new
> one.  When creating it, the internal status of the quota of the old
> scheme is not preserved.  As a result, charging of the quota starts from
> zero after the online tuning.  The data that collected to estimate the
> throughput of the scheme's action is also reset, and therefore the
> estimation should start from the scratch again.  Because the throughput
> estimation is being used to convert the time quota to the effective size
> quota, this could result in temporal time quota inaccuracy.  It would be
> recovered over time, though.  In short, the quota accuracy could be
> temporarily degraded after online parameters update.
> 
> Fix the problem by checking the case and copying the internal fields for
> the status.
> 
> Link: https://lkml.kernel.org/r/20240216194025.9207-1-sj@kernel.org
> Link: https://lkml.kernel.org/r/20240216194025.9207-2-sj@kernel.org
> Fixes: e035c280f6df ("mm/damon/reclaim: support online inputs update")
> Signed-off-by: SeongJae Park <sj@kernel.org>
> Cc: <stable@vger.kernel.org>	[5.19+]
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> (cherry picked from commit 1b0ca4e4ff10a2c8402e2cf70132c683e1c772e4)
> ---
>  mm/damon/reclaim.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 

Now queued up, thanks.

greg k-h
diff mbox series

Patch

diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
index 162c9b1ca00f..cc337e94acfd 100644
--- a/mm/damon/reclaim.c
+++ b/mm/damon/reclaim.c
@@ -141,9 +141,20 @@  static struct damos *damon_reclaim_new_scheme(void)
 			&damon_reclaim_wmarks);
 }
 
+static void damon_reclaim_copy_quota_status(struct damos_quota *dst,
+		struct damos_quota *src)
+{
+	dst->total_charged_sz = src->total_charged_sz;
+	dst->total_charged_ns = src->total_charged_ns;
+	dst->charged_sz = src->charged_sz;
+	dst->charged_from = src->charged_from;
+	dst->charge_target_from = src->charge_target_from;
+	dst->charge_addr_from = src->charge_addr_from;
+}
+
 static int damon_reclaim_apply_parameters(void)
 {
-	struct damos *scheme;
+	struct damos *scheme, *old_scheme;
 	int err = 0;
 
 	err = damon_set_attrs(ctx, &damon_reclaim_mon_attrs);
@@ -154,6 +165,11 @@  static int damon_reclaim_apply_parameters(void)
 	scheme = damon_reclaim_new_scheme();
 	if (!scheme)
 		return -ENOMEM;
+	if (!list_empty(&ctx->schemes)) {
+		damon_for_each_scheme(old_scheme, ctx)
+			damon_reclaim_copy_quota_status(&scheme->quota,
+					&old_scheme->quota);
+	}
 	damon_set_schemes(ctx, &scheme, 1);
 
 	return damon_set_region_biggest_system_ram_default(target,