From: Kees Cook <keescook@chromium.org>
To: Joel Fernandes <joelaf@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Anton Vorontsov <anton@enomsg.org>,
Colin Cross <ccross@android.com>, Tony Luck <tony.luck@intel.com>
Subject: Re: [PATCH 5/7] ramoops: Split ftrace buffer space into per-CPU zones
Date: Mon, 10 Oct 2016 17:00:50 -0700 [thread overview]
Message-ID: <CAGXu5jJhFfomZu6wbgokxAAnCwVwuP3GM_G+vZGWhywb2FFWVQ@mail.gmail.com> (raw)
In-Reply-To: <CAGXu5jKErf=g58s7FUa+6RBx3rAj_SM_z7Fp5zNLAXdrf7sorQ@mail.gmail.com>
On Mon, Oct 10, 2016 at 4:59 PM, Kees Cook <keescook@chromium.org> wrote:
> On Sun, Oct 9, 2016 at 10:15 AM, Joel Fernandes <joelaf@google.com> wrote:
>> On Fri, Oct 7, 2016 at 10:28 PM, Joel Fernandes <joelaf@google.com> wrote:
>>> If FTRACE_PER_CPU flag is passed to ramoops pdata, split the space into
>>> multiple zones depending on the number of CPUs.
>>>
>>> This speeds up the performance of function tracing by about 280% in my tests as
>>> we avoid the locking. The trade off being lesser space available per CPU. Let
>>> the ramoops user decide which option they want based on pdata flag.
>>>
>>> Signed-off-by: Joel Fernandes <joelaf@google.com>
>>> ---
>>> fs/pstore/ram.c | 70 +++++++++++++++++++++++++++++++++++-----------
>>> include/linux/pstore_ram.h | 3 ++
>>> 2 files changed, 56 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
>> [..]
>>> @@ -391,14 +418,21 @@ static void ramoops_free_przs(struct ramoops_context *cxt)
>>> {
>>> int i;
>>>
>>> - if (!cxt->przs)
>>> - return;
>>> + /* Free dump PRZs */
>>> + if (cxt->przs) {
>>> + for (i = 0; i < cxt->max_dump_cnt; i++)
>>> + persistent_ram_free(cxt->przs[i]);
>>>
>>> - for (i = 0; i < cxt->max_dump_cnt; i++)
>>> - persistent_ram_free(cxt->przs[i]);
>>> + kfree(cxt->przs);
>>> + cxt->max_dump_cnt = 0;
>>> + }
>>>
>>> - kfree(cxt->przs);
>>> - cxt->max_dump_cnt = 0;
>>> + /* Free ftrace PRZs */
>>> + if (cxt->fprzs) {
>>> + for (i = 0; i < nr_cpu_ids; i++)
>>> + persistent_ram_free(cxt->przs[i]);
>>
>> I am supposed to free fprzs[i] here, instead of przs[i]. Also need to
>> check flag and free correct number of zones. Will fix for v2, sorry
>> about that.
>
> I think the cpu id needs to be bounds-checked against the size of the
> allocation. In theory, CPU hot-plug could grow the number of CPUs
> after pstore is initialized.
Oh, also, this new flag needs to be explosed as a module parameter and
Device Tree flag as well, so it's available for more than just the
dummy driver. :)
-Kees
--
Kees Cook
Nexus Security
next prev parent reply other threads:[~2016-10-11 0:00 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-08 5:28 [RFC 0/7] pstore: Improve performance of ftrace backend with ramoops Joel Fernandes
2016-10-08 5:28 ` [PATCH 1/7] pstore: Make spinlock per zone instead of global Joel Fernandes
2016-10-08 5:44 ` Joel Fernandes
2016-10-10 23:44 ` Kees Cook
2016-10-08 5:28 ` [PATCH 2/7] pstore: locking: dont lock unless caller asks to Joel Fernandes
2016-10-10 23:48 ` Kees Cook
2016-10-11 14:41 ` Joel Fernandes
2016-10-08 5:28 ` [PATCH 3/7] pstore: Remove case of PSTORE_TYPE_PMSG write using deprecated function Joel Fernandes
2016-10-10 23:52 ` Kees Cook
2016-10-11 14:46 ` Joel Fernandes
2016-10-08 5:28 ` [PATCH 4/7] pstore: Make ramoops_init_przs generic for other prz arrays Joel Fernandes
2016-10-10 23:55 ` Kees Cook
2016-10-08 5:28 ` [PATCH 5/7] ramoops: Split ftrace buffer space into per-CPU zones Joel Fernandes
2016-10-09 17:15 ` Joel Fernandes
2016-10-10 23:59 ` Kees Cook
2016-10-11 0:00 ` Kees Cook [this message]
2016-10-16 17:40 ` Joel Fernandes
2016-10-18 20:37 ` Kees Cook
2016-10-08 5:28 ` [PATCH 6/7] pstore: Add support to store timestamp counter in ftrace records Joel Fernandes
2016-10-08 5:28 ` [PATCH 7/7] pstore: Merge per-CPU ftrace zones into one zone for output Joel Fernandes
2016-10-11 9:57 ` [RFC 0/7] pstore: Improve performance of ftrace backend with ramoops Steven Rostedt
2016-10-20 7:17 [PATCH " Joel Fernandes
2016-10-20 7:17 ` [PATCH 5/7] ramoops: Split ftrace buffer space into per-CPU zones Joel Fernandes
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