From: Yujie Liu <yujie.liu@intel.com>
To: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: <x86@kernel.org>, <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Daniel Sneddon <daniel.sneddon@linux.intel.com>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Alexandre Chartre <alexandre.chartre@oracle.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Peter Zijlstra <peterz@infradead.org>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
Sean Christopherson <seanjc@google.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Nikolay Borisov <nik.borisov@suse.com>,
"KP Singh" <kpsingh@kernel.org>, Waiman Long <longman@redhat.com>,
"Borislav Petkov" <bp@alien8.de>, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH v4 1/5] x86/bugs: Only harden syscalls when needed
Date: Mon, 20 May 2024 13:21:32 +0800 [thread overview]
Message-ID: <Zkrd3Cnh8EBXwGAR@yujie-X299> (raw)
In-Reply-To: <20240507051741.4crk2pd2fuh4euyd@treble>
On Mon, May 06, 2024 at 10:17:41PM -0700, Josh Poimboeuf wrote:
> On Mon, Apr 22, 2024 at 04:09:33PM +0800, Yujie Liu wrote:
> > On Fri, Apr 19, 2024 at 02:09:47PM -0700, Josh Poimboeuf wrote:
> > > Syscall hardening (converting the syscall indirect branch to a series of
> > > direct branches) has shown some performance regressions:
> > >
> > > - Red Hat internal testing showed up to 12% slowdowns in database
> > > benchmark testing on Sapphire Rapids when the DB was stressed with 80+
> > > users to cause contention.
> > >
> > > - The kernel test robot's will-it-scale benchmarks showed significant
> > > regressions on Skylake with IBRS:
> > > https://lkml.kernel.org/lkml/202404191333.178a0eed-yujie.liu@intel.com
> >
> > To clarify, we reported a +1.4% improvement (not regression) of
> > will-it-scale futex4 benchmark on Skylake. Meanwhile we did observe some
> > regressions by running other benchmarks on Ice Lake, such as:
> >
> > stress-ng.null.ops_per_sec -4.0% regression on Intel Xeon Gold 6346 (Ice Lake)
> > unixbench.fsbuffer.throughput -1.4% regression on Intel Xeon Gold 6346 (Ice Lake)
>
> Thanks for clarifying that. I'm not sure what I was looking at.
>
> I also saw your email where Ice Lake showed a ~10% regression for
> 1e3ad78334a6. Unfortunately my patch wouldn't help with that, as it's
> designed to help with older systems (e.g., Skylake) and newer (e.g.,
> Sapphire Rapids) but not Ice/Cascade Lake.
>
> Whether 1e3ad78334a6 helps or hurts seems very workload-dependent.
>
> It would be especially interesting to see if my patch helps on the newer
> systems which have the HW mitigation: Raptor Lake, Meteor Lake, Sapphire
> Rapids, Emerald Rapids.
>
> For now, maybe I'll just table this patch until we have more data.
FYI, we tested this patch on a Sapphire Rapids machine in our test
infrastructure. There are both improvements and regressions across
different benchmarks, which does show that the impact may be very
workload-dependent.
Intel Xeon Platinum 8480CTDX (Sapphire Rapids) with 512G Memory:
+-----------------------+----------+---------------+------------------+
| | mainline | + this patch | (percent change) |
+-----------------------+----------+---------------+------------------+
| will-it-scale.futex4 | 5015892 | 5118744 | +2.05% |
+-----------------------+----------+---------------+------------------+
| will-it-scale.pread1 | 2720498 | 2721206 | +0.03% |
+-----------------------+----------+---------------+------------------+
| will-it-scale.pwrite1 | 2143302 | 2164511 | +0.99% |
+-----------------------+----------+---------------+------------------+
| will-it-scale.poll1 | 4046943 | 4095046 | +1.19% |
+-----------------------+----------+---------------+------------------+
| stress-ng.null | 19400 | 18689 | -3.66% |
+-----------------------+----------+---------------+------------------+
| unixbench.fsbuffer | 369494 | 364181 | -1.44% |
+-----------------------+----------+---------------+------------------+
Thanks,
Yujie
next prev parent reply other threads:[~2024-05-20 5:21 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-19 21:09 [PATCH 0/5] x86/bugs: more BHI fixes Josh Poimboeuf
2024-04-19 21:09 ` [PATCH v4 1/5] x86/bugs: Only harden syscalls when needed Josh Poimboeuf
2024-04-22 8:09 ` Yujie Liu
2024-05-07 5:17 ` Josh Poimboeuf
2024-05-20 5:21 ` Yujie Liu [this message]
2024-04-19 21:09 ` [PATCH v4 2/5] cpu/speculation: Fix CPU mitigation defaults for !x86 Josh Poimboeuf
2024-04-20 0:09 ` Sean Christopherson
2024-04-23 14:10 ` Sean Christopherson
2024-04-24 5:35 ` Josh Poimboeuf
2024-04-19 21:09 ` [PATCH v4 3/5] x86/syscall: Mark exit[_group] syscall handlers __noreturn Josh Poimboeuf
2024-04-20 13:58 ` Paul E. McKenney
2024-04-21 5:25 ` Josh Poimboeuf
2024-04-21 20:40 ` Paul McKenney
2024-04-21 21:47 ` Paul McKenney
2024-05-02 23:48 ` Paul McKenney
2024-05-03 15:38 ` Paul E. McKenney
2024-05-03 19:56 ` Josh Poimboeuf
2024-05-03 20:44 ` Josh Poimboeuf
2024-05-03 23:33 ` Paul E. McKenney
2024-05-03 23:48 ` Josh Poimboeuf
2024-05-04 16:48 ` Paul E. McKenney
2024-04-19 21:09 ` [PATCH v4 4/5] x86/bugs: Remove duplicate Spectre cmdline option descriptions Josh Poimboeuf
2024-04-19 21:09 ` [PATCH v4 5/5] x86/bugs: Add 'spectre_bhi=vmexit' cmdline option Josh Poimboeuf
2024-04-19 21:46 ` Josh Poimboeuf
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