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Sun, 17 Oct 2021 00:58:49 +0800 From: xhao@linux.alibaba.com Reply-To: xhao@linux.alibaba.com Subject: Re: [PATCH] mm/damon/core: Optimize kdamod.%d thread creation code To: sjpark@amazon.de Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20211016165616.95849-1-xhao@linux.alibaba.com> Message-ID: <41bb07ec-8ec3-5c83-027b-172d8f2bd7a1@linux.alibaba.com> Date: Sun, 17 Oct 2021 00:58:46 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20211016165616.95849-1-xhao@linux.alibaba.com> Content-Type: text/plain; charset=utf-8; format=flowed X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 8D00510000AA X-Stat-Signature: tqryok97tgy4qh8k31b1njombgx584tr Authentication-Results: imf12.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf12.hostedemail.com: domain of xhao@linux.alibaba.com designates 115.124.30.45 as permitted sender) smtp.mailfrom=xhao@linux.alibaba.com X-HE-Tag: 1634403533-228647 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2021/10/17 =E4=B8=8A=E5=8D=8812:56, 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 > --- > 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, struc= t damon_target *t) > list_add_tail(&t->list, &ctx->adaptive_targets); > } > =20 > +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 =3D -EBUSY; > =20 > mutex_lock(&ctx->kdamond_lock); > - if (!ctx->kdamond) { > + ctx->kdamond_stop =3D false; > + ctx->kdamond =3D kthread_run(kdamond_fn, ctx, "kdamond.%d", > + nr_running_ctxs); > + if (IS_ERR(ctx->kdamond)) { > + err =3D PTR_ERR(ctx->kdamond); > + ctx->kdamond =3D 0; > + } else { > err =3D 0; > - ctx->kdamond_stop =3D false; > - ctx->kdamond =3D kthread_run(kdamond_fn, ctx, "kdamond.%d", > - nr_running_ctxs); > - if (IS_ERR(ctx->kdamond)) { > - err =3D PTR_ERR(ctx->kdamond); > - ctx->kdamond =3D 0; > - } > } > mutex_unlock(&ctx->kdamond_lock); > =20 > @@ -347,10 +351,12 @@ int damon_start(struct damon_ctx **ctxs, int nr_c= txs) > } > =20 > for (i =3D 0; i < nr_ctxs; i++) { > - err =3D __damon_start(ctxs[i]); > - if (err) > - break; > - nr_running_ctxs++; > + if (!damon_target_empty(ctxs[i]) && !ctxs[i]->kdamond) { > + err =3D __damon_start(ctxs[i]); > + if (err) > + break; > + nr_running_ctxs++; > + } > } > mutex_unlock(&damon_lock); > =20 --=20 Best Regards! Xin Hao