The patch titled
Subject: mm/damon/sysfs: fix unnecessary monitoring results removal when online-commit inputs
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-damon-sysfs-remove-requested-targets-when-online-commit-inputs-fix.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-sysfs-remove-requested-targets-when-online-commit-inputs-fix.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: SeongJae Park <sj@xxxxxxxxxx>
Subject: mm/damon/sysfs: fix unnecessary monitoring results removal when online-commit inputs
Date: Sat, 28 Oct 2023 21:33:53 +0000
Commit db27869df6ed ("mm/damon/sysfs: remove requested targets when
online-commit inputs") of mm-hotfixes-unstable tree[1] makes all targets
to removed and then added again based on the user input, for online-commit
inputs. The commit says it is inefficient but ok as below:
This could cause unnecessary memory dealloc and realloc operations,
but this is not a hot code path. Also, note that damon_target is
stateless, and hence no data is lost
But that's not true. 'struct target' is containing the monitoring results
('->regions_list'). As a result, the patch makes all previous monitoring
results to be removed for every online-commit inputs. Fix it by removing
targets only when really changed or removal is requested.
[1] https://lore.kernel.org/damon/20231022210735.46409-2-sj@xxxxxxxxxx/
Link: https://lkml.kernel.org/r/20231028213353.45397-1-sj@xxxxxxxxxx
Fixes: db27869df6ed ("mm/damon/sysfs: remove requested targets when online-commit inputs") # mm-hotfixes-unstable
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/damon/sysfs.c | 44 +++++++++++++++++++++++++++++++++++++++-----
1 file changed, 39 insertions(+), 5 deletions(-)
--- a/mm/damon/sysfs.c~mm-damon-sysfs-remove-requested-targets-when-online-commit-inputs-fix
+++ a/mm/damon/sysfs.c
@@ -1150,23 +1150,57 @@ destroy_targets_out:
return err;
}
+static int damon_sysfs_update_target(struct damon_target *target,
+ struct damon_ctx *ctx,
+ struct damon_sysfs_target *sys_target)
+{
+ struct pid *pid;
+ struct damon_region *r, *next;
+
+ if (!damon_target_has_pid(ctx))
+ return 0;
+
+ pid = find_get_pid(sys_target->pid);
+ if (!pid)
+ return -EINVAL;
+
+ /* no change to the target */
+ if (pid == target->pid) {
+ put_pid(pid);
+ return 0;
+ }
+
+ /* remove old monitoring results and update the target's pid */
+ damon_for_each_region_safe(r, next, target)
+ damon_destroy_region(r, target);
+ put_pid(target->pid);
+ target->pid = pid;
+ return 0;
+}
+
static int damon_sysfs_set_targets(struct damon_ctx *ctx,
struct damon_sysfs_targets *sysfs_targets)
{
struct damon_target *t, *next;
- int i, err;
+ int i = 0, err;
/* Multiple physical address space monitoring targets makes no sense */
if (ctx->ops.id == DAMON_OPS_PADDR && sysfs_targets->nr > 1)
return -EINVAL;
damon_for_each_target_safe(t, next, ctx) {
- if (damon_target_has_pid(ctx))
- put_pid(t->pid);
- damon_destroy_target(t);
+ if (i < sysfs_targets->nr) {
+ damon_sysfs_update_target(t, ctx,
+ sysfs_targets->targets_arr[i]);
+ } else {
+ if (damon_target_has_pid(ctx))
+ put_pid(t->pid);
+ damon_destroy_target(t);
+ }
+ i++;
}
- for (i = 0; i < sysfs_targets->nr; i++) {
+ for (; i < sysfs_targets->nr; i++) {
struct damon_sysfs_target *st = sysfs_targets->targets_arr[i];
err = damon_sysfs_add_target(st, ctx);
_
Patches currently in -mm which might be from sj@xxxxxxxxxx are
mm-damon-sysfs-remove-requested-targets-when-online-commit-inputs.patch
mm-damon-sysfs-remove-requested-targets-when-online-commit-inputs-fix.patch
