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SubjectRe: [PATCH] mm/damon/core: Optimize kdamod.%d thread creation code
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On 2021/10/17 上午12:56, Xin Hao wrote:
> When the ctx->adaptive_targets list is empty,
> i did some test on monitor_on interface like this.
>
> echo on > /sys/kernel/debug/damon/monitor_on
> [ 851.988307] damon: kdamond (5390) starts
>
> Though the ctx->adaptive_targets list is empty, but the
> kthread_run still be called, and the kdamond.x thread still
> be created, this is meaningless, so t

Sorry there made a mistake, i will send a new one.

>
> So there adds a judgment. only if the ctx->adaptive_targets
> list is not empty, and ctx->kdamond pointer is NULL, then call
> the __damon_start function.
>
> Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
> ---
> mm/damon/core.c | 30 ++++++++++++++++++------------
> 1 file changed, 18 insertions(+), 12 deletions(-)
>
> diff --git a/mm/damon/core.c b/mm/damon/core.c
> index 30e9211f494a..998c707fdca2 100644
> --- a/mm/damon/core.c
> +++ b/mm/damon/core.c
> @@ -107,6 +107,11 @@ void damon_add_target(struct damon_ctx *ctx, struct damon_target *t)
> list_add_tail(&t->list, &ctx->adaptive_targets);
> }
>
> +static int damon_target_empty(struct damon_ctx *ctx)
> +{
> + return list_empty(&ctx->adaptive_targets);
> +}
> +
> static void damon_del_target(struct damon_target *t)
> {
> list_del(&t->list);
> @@ -307,15 +312,14 @@ static int __damon_start(struct damon_ctx *ctx)
> int err = -EBUSY;
>
> mutex_lock(&ctx->kdamond_lock);
> - if (!ctx->kdamond) {
> + ctx->kdamond_stop = false;
> + ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond.%d",
> + nr_running_ctxs);
> + if (IS_ERR(ctx->kdamond)) {
> + err = PTR_ERR(ctx->kdamond);
> + ctx->kdamond = 0;
> + } else {
> err = 0;
> - ctx->kdamond_stop = false;
> - ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond.%d",
> - nr_running_ctxs);
> - if (IS_ERR(ctx->kdamond)) {
> - err = PTR_ERR(ctx->kdamond);
> - ctx->kdamond = 0;
> - }
> }
> mutex_unlock(&ctx->kdamond_lock);
>
> @@ -347,10 +351,12 @@ int damon_start(struct damon_ctx **ctxs, int nr_ctxs)
> }
>
> for (i = 0; i < nr_ctxs; i++) {
> - err = __damon_start(ctxs[i]);
> - if (err)
> - break;
> - nr_running_ctxs++;
> + if (!damon_target_empty(ctxs[i]) && !ctxs[i]->kdamond) {
> + err = __damon_start(ctxs[i]);
> + if (err)
> + break;
> + nr_running_ctxs++;
> + }
> }
> mutex_unlock(&damon_lock);
>

--
Best Regards!
Xin Hao

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