From: Andrew Morton <akpm@linux-foundation.org>
To: "Joel Fernandes (Google)" <joel@joelfernandes.org>
Cc: linux-kernel@vger.kernel.org,
Alexey Dobriyan <adobriyan@gmail.com>,
Borislav Petkov <bp@alien8.de>,
Brendan Gregg <bgregg@netflix.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Christian Hansen <chansen3@cisco.com>,
dancol@google.com, fmayer@google.com,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
joelaf@google.com, Jonathan Corbet <corbet@lwn.net>,
Kees Cook <keescook@chromium.org>,
kernel-team@android.com, linux-api@vger.kernel.org,
linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, Michal Hocko <mhocko@suse.com>,
Mike Rapoport <rppt@linux.ibm.com>,
minchan@kernel.org, namhyung@google.com, paulmck@linux.ibm.com,
Robin Murphy <robin.murphy@arm.com>, Roman Gushchin <guro@fb.com>,
Stephen Rothwell <sfr@canb.auug.org.au>,
surenb@google.com, Thomas Gleixner <tglx@linutronix.de>,
tkjos@google.com, Vladimir Davydov <vdavydov.dev@gmail.com>,
Vlastimil Babka <vbabka@suse.cz>, Will Deacon <will@kernel.org>,
Brendan Gregg <brendan.d.gregg@gmail.com>
Subject: Re: [PATCH v4 1/5] mm/page_idle: Add per-pid idle page tracking using virtual indexing
Date: Tue, 6 Aug 2019 15:19:21 -0700 [thread overview]
Message-ID: <20190806151921.edec128271caccb5214fc1bd@linux-foundation.org> (raw)
In-Reply-To: <20190805170451.26009-1-joel@joelfernandes.org>
(cc Brendan's other email address, hoping for review input ;))
On Mon, 5 Aug 2019 13:04:47 -0400 "Joel Fernandes (Google)" <joel@joelfernandes.org> wrote:
> The page_idle tracking feature currently requires looking up the pagemap
> for a process followed by interacting with /sys/kernel/mm/page_idle.
> Looking up PFN from pagemap in Android devices is not supported by
> unprivileged process and requires SYS_ADMIN and gives 0 for the PFN.
>
> This patch adds support to directly interact with page_idle tracking at
> the PID level by introducing a /proc/<pid>/page_idle file. It follows
> the exact same semantics as the global /sys/kernel/mm/page_idle, but now
> looking up PFN through pagemap is not needed since the interface uses
> virtual frame numbers, and at the same time also does not require
> SYS_ADMIN.
>
> In Android, we are using this for the heap profiler (heapprofd) which
> profiles and pin points code paths which allocates and leaves memory
> idle for long periods of time. This method solves the security issue
> with userspace learning the PFN, and while at it is also shown to yield
> better results than the pagemap lookup, the theory being that the window
> where the address space can change is reduced by eliminating the
> intermediate pagemap look up stage. In virtual address indexing, the
> process's mmap_sem is held for the duration of the access.
Quite a lot of changes to the page_idle code. Has this all been
runtime tested on architectures where
CONFIG_HAVE_ARCH_PTE_SWP_PGIDLE=n? That could be x86 with a little
Kconfig fiddle-for-testing-purposes.
> 8 files changed, 376 insertions(+), 45 deletions(-)
Quite a lot of new code unconditionally added to major architectures.
Are we confident that everyone will want this feature?
>
> ...
>
> +static int proc_page_idle_open(struct inode *inode, struct file *file)
> +{
> + struct mm_struct *mm;
> +
> + mm = proc_mem_open(inode, PTRACE_MODE_READ);
> + if (IS_ERR(mm))
> + return PTR_ERR(mm);
> + file->private_data = mm;
> + return 0;
> +}
> +
> +static int proc_page_idle_release(struct inode *inode, struct file *file)
> +{
> + struct mm_struct *mm = file->private_data;
> +
> + if (mm)
I suspect the test isn't needed? proc_page_idle_release) won't be
called if proc_page_idle_open() failed?
> + mmdrop(mm);
> + return 0;
> +}
>
> ...
>
next prev parent reply other threads:[~2019-08-06 22:19 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-05 17:04 [PATCH v4 1/5] mm/page_idle: Add per-pid idle page tracking using virtual indexing Joel Fernandes (Google)
2019-08-05 17:04 ` [PATCH v4 2/5] [RFC] x86: Add support for idle bit in swap PTE Joel Fernandes (Google)
2019-08-05 17:04 ` [PATCH v4 3/5] [RFC] arm64: " Joel Fernandes (Google)
2019-08-06 8:42 ` Michal Hocko
2019-08-06 10:36 ` Joel Fernandes
2019-08-06 10:47 ` Michal Hocko
2019-08-06 11:07 ` Minchan Kim
2019-08-06 11:14 ` Michal Hocko
2019-08-06 11:26 ` Joel Fernandes
2019-08-06 11:14 ` Joel Fernandes
2019-08-06 11:57 ` Michal Hocko
2019-08-06 13:43 ` Joel Fernandes
2019-08-06 14:09 ` Michal Hocko
2019-08-06 14:47 ` Minchan Kim
2019-08-06 15:20 ` Joel Fernandes
2019-08-05 17:04 ` [PATCH v4 4/5] page_idle: Drain all LRU pagevec before idle tracking Joel Fernandes (Google)
2019-08-06 8:43 ` Michal Hocko
2019-08-06 10:45 ` Joel Fernandes
2019-08-06 10:51 ` Michal Hocko
2019-08-06 11:19 ` Joel Fernandes
2019-08-06 11:44 ` Michal Hocko
2019-08-06 13:48 ` Joel Fernandes
2019-08-05 17:04 ` [PATCH v4 5/5] doc: Update documentation for page_idle virtual address indexing Joel Fernandes (Google)
2019-08-06 8:56 ` [PATCH v4 1/5] mm/page_idle: Add per-pid idle page tracking using virtual indexing Michal Hocko
2019-08-06 10:47 ` Joel Fernandes
2019-08-06 22:19 ` Andrew Morton [this message]
2019-08-07 10:00 ` Joel Fernandes
2019-08-07 20:01 ` Andrew Morton
2019-08-07 20:44 ` Joel Fernandes
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