From: SeongJae Park <sjpark@amazon.com>
To: Shakeel Butt <shakeelb@google.com>
Cc: SeongJae Park <sjpark@amazon.com>,
Andrea Arcangeli <aarcange@redhat.com>, <acme@kernel.org>,
<alexander.shishkin@linux.intel.com>, <amit@kernel.org>,
<benh@kernel.crashing.org>, <brendan.d.gregg@gmail.com>,
Brendan Higgins <brendanhiggins@google.com>,
Qian Cai <cai@lca.pw>, Colin Ian King <colin.king@canonical.com>,
Jonathan Corbet <corbet@lwn.net>,
"David Hildenbrand" <david@redhat.com>, <dwmw@amazon.com>,
Marco Elver <elver@google.com>, "Du, Fan" <fan.du@intel.com>,
<foersleo@amazon.de>, "Greg Thelen" <gthelen@google.com>,
Ian Rogers <irogers@google.com>, <jolsa@redhat.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Mark Rutland <mark.rutland@arm.com>, Mel Gorman <mgorman@suse.de>,
Minchan Kim <minchan@kernel.org>, Ingo Molnar <mingo@redhat.com>,
<namhyung@kernel.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
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Steven Rostedt <rostedt@goodmis.org>,
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Shuah Khan <shuah@kernel.org>, <sj38.park@gmail.com>,
<snu@amazon.de>, Vlastimil Babka <vbabka@suse.cz>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Yang Shi <yang.shi@linux.alibaba.com>,
Huang Ying <ying.huang@intel.com>, <zgf574564920@gmail.com>,
<linux-damon@amazon.com>, Linux MM <linux-mm@kvack.org>,
<linux-doc@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v23 07/15] mm/damon: Implement a debugfs-based user space interface
Date: Tue, 2 Feb 2021 16:45:06 +0100 [thread overview]
Message-ID: <20210202154506.29682-1-sjpark@amazon.com> (raw)
In-Reply-To: <CALvZod7tv=z3XwGx3pn5qNHQd1EAnhvBaM3EGRjWmo7G2RJEuw@mail.gmail.com>
On Tue, 2 Feb 2021 07:07:24 -0800 Shakeel Butt <shakeelb@google.com> wrote:
> On Tue, Feb 2, 2021 at 2:30 AM SeongJae Park <sjpark@amazon.com> wrote:
> >
> >> On Mon, 1 Feb 2021 09:37:39 -0800 Shakeel Butt <shakeelb@google.com> wrote:
> >>
> >>> On Tue, Dec 15, 2020 at 3:59 AM SeongJae Park <sjpark@amazon.com> wrote:
> >>>>
> >>>> From: SeongJae Park <sjpark@amazon.de>
> >>>>
> >>>> DAMON is designed to be used by kernel space code such as the memory
> >>>> management subsystems, and therefore it provides only kernel space API.
> >>>
> >>> Which kernel space APIs are being referred here?
> >>
> >> The symbols in 'include/linux/damon.h'
> >>
> >>>
> >>>> That said, letting the user space control DAMON could provide some
> >>>> benefits to them. For example, it will allow user space to analyze
> >>>> their specific workloads and make their own special optimizations.
> >>>>
> >>>> For such cases, this commit implements a simple DAMON application kernel
> >>>> module, namely 'damon-dbgfs', which merely wraps the DAMON api and
> >>>> exports those to the user space via the debugfs.
> >>>>
> >> [...]
> >>>> +static ssize_t dbgfs_target_ids_write(struct file *file,
> >>>> + const char __user *buf, size_t count, loff_t *ppos)
> >>>> +{
> >>>> + struct damon_ctx *ctx = file->private_data;
> >>>> + char *kbuf, *nrs;
> >>>> + unsigned long *targets;
> >>>> + ssize_t nr_targets;
> >>>> + ssize_t ret = count;
> >>>> + int i;
> >>>> + int err;
> >>>> +
> >>>> + kbuf = user_input_str(buf, count, ppos);
> >>>> + if (IS_ERR(kbuf))
> >>>> + return PTR_ERR(kbuf);
> >>>> +
> >>>> + nrs = kbuf;
> >>>> +
> >>>> + targets = str_to_target_ids(nrs, ret, &nr_targets);
> >>>> + if (!targets) {
> >>>> + ret = -ENOMEM;
> >>>> + goto out;
> >>>> + }
> >>>> +
> >>>> + if (targetid_is_pid(ctx)) {
> >>>> + for (i = 0; i < nr_targets; i++)
> >>>> + targets[i] = (unsigned long)find_get_pid(
> >>>> + (int)targets[i]);
> >>>> + }
> >>>> +
> >>>> + mutex_lock(&ctx->kdamond_lock);
> >>>> + if (ctx->kdamond) {
> >>>> + ret = -EINVAL;
> >>>> + goto unlock_out;
> >>>
> >>> You need to put_pid on the targets array.
> >>
> >> Good catch!
> >>
> >>>
> >>>> + }
> >>>> +
> >>>> + err = damon_set_targets(ctx, targets, nr_targets);
> >>>> + if (err)
> >>>> + ret = err;
> >>>
> >>> You need to handle the partial failure from damon_set_targets().
> >>
> >> My intention is to keep partial success as is.
> >
> > But, we should put_pid() partial failures... I will simply make this to
> > completely fail with no registered target.
> >
>
> You can simplify by simply restricting to one pid/target per each write syscall.
Right, thanks for the suggestion. However, I already almost finished writing
the fix. If there is no other concern, I'd like to keep current interface.
Thanks,
SeongJae Park
next prev parent reply other threads:[~2021-02-02 15:46 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-02 10:29 [PATCH v23 07/15] mm/damon: Implement a debugfs-based user space interface SeongJae Park
2021-02-02 15:07 ` Shakeel Butt
2021-02-02 15:45 ` SeongJae Park [this message]
2021-02-02 16:08 ` Shakeel Butt
-- strict thread matches above, loose matches on Subject: below --
2020-12-15 11:54 [PATCH v23 00/15] Introduce Data Access MONitor (DAMON) SeongJae Park
2020-12-15 11:54 ` [PATCH v23 07/15] mm/damon: Implement a debugfs-based user space interface SeongJae Park
2021-02-01 17:37 ` Shakeel Butt
2021-02-02 10:00 ` SeongJae Park
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