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(-)
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,