linux-kernel - Re: [RFC PATCH v2 06/20] tracing/filters: Optimise scalar vs cpumask filtering when the user mask is a single CPU

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <xhsmh1qgos4xi.mognet@vschneid.remote.csb>
Date:   Mon, 31 Jul 2023 12:20:41 +0100
From:   Valentin Schneider <vschneid@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, kvm@...r.kernel.org, linux-mm@...ck.org,
        bpf@...r.kernel.org, x86@...nel.org, rcu@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Josh Triplett <josh@...htriplett.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Zqiang <qiang.zhang1211@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Christoph Hellwig <hch@...radead.org>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Jason Baron <jbaron@...mai.com>,
        Kees Cook <keescook@...omium.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Juerg Haefliger <juerg.haefliger@...onical.com>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Nadav Amit <namit@...are.com>,
        Dan Carpenter <error27@...il.com>,
        Chuang Wang <nashuiliang@...il.com>,
        Yang Jihong <yangjihong1@...wei.com>,
        Petr Mladek <pmladek@...e.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>, Song Liu <song@...nel.org>,
        Julian Pidancet <julian.pidancet@...cle.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Dionna Glaze <dionnaglaze@...gle.com>,
        Thomas Weißschuh <linux@...ssschuh.net>,
        Juri Lelli <juri.lelli@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Yair Podemsky <ypodemsk@...hat.com>
Subject: Re: [RFC PATCH v2 06/20] tracing/filters: Optimise scalar vs
 cpumask filtering when the user mask is a single CPU

On 29/07/23 15:55, Steven Rostedt wrote:
> On Thu, 20 Jul 2023 17:30:42 +0100
> Valentin Schneider <vschneid@...hat.com> wrote:
>
>> Steven noted that when the user-provided cpumask contains a single CPU,
>> then the filtering function can use a scalar as input instead of a
>> full-fledged cpumask.
>>
>> When the mask contains a single CPU, directly re-use the unsigned field
>> predicate functions. Transform '&' into '==' beforehand.
>>
>> Suggested-by: Steven Rostedt <rostedt@...dmis.org>
>> Signed-off-by: Valentin Schneider <vschneid@...hat.com>
>> ---
>>  kernel/trace/trace_events_filter.c | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
>> index 2fe65ddeb34ef..54d642fabb7f1 100644
>> --- a/kernel/trace/trace_events_filter.c
>> +++ b/kernel/trace/trace_events_filter.c
>> @@ -1750,7 +1750,7 @@ static int parse_pred(const char *str, void *data,
>>               * then we can treat it as a scalar input.
>>               */
>>              single = cpumask_weight(pred->mask) == 1;
>> -		if (single && field->filter_type == FILTER_CPUMASK) {
>> +		if (single && field->filter_type != FILTER_CPU) {
>>                      pred->val = cpumask_first(pred->mask);
>>                      kfree(pred->mask);
>>              }
>> @@ -1761,6 +1761,11 @@ static int parse_pred(const char *str, void *data,
>>                              FILTER_PRED_FN_CPUMASK;
>>              } else if (field->filter_type == FILTER_CPU) {
>>                      pred->fn_num = FILTER_PRED_FN_CPU_CPUMASK;
>> +		} else if (single) {
>> +			pred->op = pred->op == OP_BAND ? OP_EQ : pred->op;
>
> Nit, the above can be written as:
>
>                       pred->op = pret->op != OP_BAND ? : OP_EQ;
>

That's neater, thanks!

> -- Steve
>
>
>> +			pred->fn_num = select_comparison_fn(pred->op, field->size, false);
>> +			if (pred->op == OP_NE)
>> +				pred->not = 1;
>>              } else {
>>                      switch (field->size) {
>>                      case 8: