From: Peter Zijlstra <peterz@infradead.org>
To: Fenghua Yu <fenghua.yu@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
H Peter Anvin <hpa@zytor.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Dave Hansen <dave.hansen@intel.com>,
Ashok Raj <ashok.raj@intel.com>,
Ravi V Shankar <ravi.v.shankar@intel.com>,
Xiaoyao Li <xiaoyao.li@intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>,
kvm@vger.kernel.org
Subject: Re: [PATCH v4 02/17] drivers/net/b44: Align pwol_mask to unsigned long for better performance
Date: Mon, 4 Mar 2019 11:00:22 +0100 [thread overview]
Message-ID: <20190304100022.GA32477@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1551494711-213533-3-git-send-email-fenghua.yu@intel.com>
On Fri, Mar 01, 2019 at 06:44:56PM -0800, Fenghua Yu wrote:
> A bit in pwol_mask is set in b44_magic_pattern automatically by set_bit.
> set_bit sets the bit in a single unsigned long location. Since pwol_mask
> may not be aligned to unsigned long, the location may cross two cache
> lines and accessing the location degradates performance. On x86, accessing
> two cache lines in locked instruction in set_bit is called split lock and
> can cause overall performance degradation.
>
> To avoid to impact performance by accessing two cache lines in set_bit,
> align pwol_mask to unsigned long.
>
> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
> ---
> drivers/net/ethernet/broadcom/b44.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/broadcom/b44.c b/drivers/net/ethernet/broadcom/b44.c
> index 97ab0dd25552..bc544b6b9c3a 100644
> --- a/drivers/net/ethernet/broadcom/b44.c
> +++ b/drivers/net/ethernet/broadcom/b44.c
> @@ -1547,7 +1547,8 @@ static void b44_setup_pseudo_magicp(struct b44 *bp)
> u32 val;
> int plen0, plen1, plen2;
> u8 *pwol_pattern;
> - u8 pwol_mask[B44_PMASK_SIZE];
> + /* Align to unsigned long for better performance in set_bit() */
> + u8 pwol_mask[B44_PMASK_SIZE] __aligned(sizeof(unsigned long));
>
> pwol_pattern = kzalloc(B44_PATTERN_SIZE, GFP_KERNEL);
> if (!pwol_pattern)
That is truly horrid code. But afaict pwol_mask is local and never
exposed to concurrency, so _why_ does it need atomic bitset in the first
place?
Would not the below be a _much_ better solution?
diff --git a/drivers/net/ethernet/broadcom/b44.c b/drivers/net/ethernet/broadcom/b44.c
index 97ab0dd25552..0b4226b406b1 100644
--- a/drivers/net/ethernet/broadcom/b44.c
+++ b/drivers/net/ethernet/broadcom/b44.c
@@ -1520,7 +1520,7 @@ static int b44_magic_pattern(u8 *macaddr, u8 *ppattern, u8 *pmask, int offset)
memset(ppattern + offset, 0xff, magicsync);
for (j = 0; j < magicsync; j++)
- set_bit(len++, (unsigned long *) pmask);
+ __set_bit(len++, (unsigned long *) pmask);
for (j = 0; j < B44_MAX_PATTERNS; j++) {
if ((B44_PATTERN_SIZE - len) >= ETH_ALEN)
@@ -1532,7 +1532,7 @@ static int b44_magic_pattern(u8 *macaddr, u8 *ppattern, u8 *pmask, int offset)
for (k = 0; k< ethaddr_bytes; k++) {
ppattern[offset + magicsync +
(j * ETH_ALEN) + k] = macaddr[k];
- set_bit(len++, (unsigned long *) pmask);
+ __set_bit(len++, (unsigned long *) pmask);
}
}
return len - 1;
next prev parent reply other threads:[~2019-03-04 10:00 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-02 2:44 [PATCH v4 00/17] x86/split_lock: Enable #AC exception for split locked accesses Fenghua Yu
2019-03-02 2:44 ` [PATCH v4 01/17] x86/common: Align cpu_caps_cleared and cpu_caps_set to unsigned long Fenghua Yu
2019-03-04 8:33 ` Paolo Bonzini
2019-03-04 10:17 ` Peter Zijlstra
2019-03-04 10:48 ` Paolo Bonzini
2019-03-04 12:44 ` Peter Zijlstra
2019-03-04 13:13 ` Paolo Bonzini
2019-03-02 2:44 ` [PATCH v4 02/17] drivers/net/b44: Align pwol_mask to unsigned long for better performance Fenghua Yu
2019-03-04 10:00 ` Peter Zijlstra [this message]
2019-03-04 14:45 ` Fenghua Yu
2019-03-04 15:27 ` Peter Zijlstra
2019-03-02 2:44 ` [PATCH v4 03/17] wlcore: Align reg_ch_conf_pending and tmp_ch_bitmap " Fenghua Yu
2019-03-04 10:11 ` Peter Zijlstra
2019-03-04 10:46 ` Paolo Bonzini
2019-03-04 12:41 ` Peter Zijlstra
2019-03-04 13:09 ` Paolo Bonzini
2019-03-04 13:30 ` Peter Zijlstra
2019-03-04 14:40 ` Fenghua Yu
2019-03-04 15:54 ` Paolo Bonzini
2019-03-02 2:44 ` [PATCH v4 04/17] x86/split_lock: Align x86_capability to unsigned long to avoid split locked access Fenghua Yu
2019-03-04 18:52 ` Dave Hansen
2019-03-04 19:15 ` Fenghua Yu
2019-03-04 19:29 ` Dave Hansen
2019-03-04 20:08 ` Peter Zijlstra
2019-03-04 20:12 ` Peter Zijlstra
2019-03-02 2:44 ` [PATCH v4 05/17] x86/cpufeatures: Enumerate IA32_CORE_CAPABILITIES MSR Fenghua Yu
2019-03-04 18:53 ` Dave Hansen
2019-03-04 18:55 ` Yu, Fenghua
2019-03-04 19:01 ` Dave Hansen
2019-03-02 2:45 ` [PATCH v4 06/17] x86/msr-index: Define IA32_CORE_CAPABILITY MSR and #AC exception for split lock bit Fenghua Yu
2019-03-02 2:45 ` [PATCH v4 07/17] x86/split_lock: Enumerate #AC for split lock by MSR IA32_CORE_CAPABILITY Fenghua Yu
2019-03-04 18:58 ` Dave Hansen
2019-03-04 18:59 ` Fenghua Yu
2019-03-04 19:19 ` Dave Hansen
2019-03-02 2:45 ` [PATCH v4 08/17] x86/clearcpuid: Support multiple clearcpuid options Fenghua Yu
2019-03-02 2:45 ` [PATCH v4 09/17] x86/clearcpuid: Support feature flag string in kernel option clearcpuid Fenghua Yu
2019-03-02 2:45 ` [PATCH v4 10/17] x86/clearcpuid: Apply cleared feature bits that are forced set before Fenghua Yu
2019-03-02 2:45 ` [PATCH v4 11/17] x86/clearcpuid: Clear CPUID bit in CPUID faulting Fenghua Yu
2019-03-04 22:04 ` kbuild test robot
2019-03-05 7:27 ` kbuild test robot
2019-03-02 2:45 ` [PATCH v4 12/17] Change document for kernel option clearcpuid Fenghua Yu
2019-03-02 2:45 ` [PATCH v4 13/17] x86/split_lock: Handle #AC exception for split lock Fenghua Yu
2019-03-02 2:45 ` [PATCH v4 14/17] x86/split_lock: Add a sysfs interface to allow user to enable or disable split lock detection on all CPUs during run time Fenghua Yu
2019-03-02 2:45 ` [PATCH v4 15/17] kvm: x86: Report CORE_CAPABILITY on GET_SUPPORTED_CPUID Fenghua Yu
2019-03-04 8:38 ` Paolo Bonzini
2019-03-04 10:47 ` Xiaoyao Li
2019-03-04 10:49 ` Paolo Bonzini
2019-03-04 11:10 ` Xiaoyao Li
2019-03-04 11:14 ` Paolo Bonzini
2019-03-04 11:21 ` Xiaoyao Li
2019-03-05 7:03 ` Xiaoyao Li
2019-03-02 2:45 ` [PATCH v4 16/17] kvm: x86: Add support IA32_CORE_CAPABILITY MSR Fenghua Yu
2019-03-04 8:42 ` Paolo Bonzini
2019-03-04 12:32 ` Xiaoyao Li
2019-03-08 6:10 ` Xiaoyao Li
2019-03-08 7:54 ` Paolo Bonzini
2019-03-08 8:03 ` Xiaoyao Li
2019-03-02 2:45 ` [PATCH v4 17/17] kvm: vmx: Emulate TEST_CTL MSR Fenghua Yu
2019-03-09 2:31 ` Xiaoyao Li
2019-03-11 13:31 ` Paolo Bonzini
2019-03-11 15:10 ` Xiaoyao Li
2019-03-11 15:21 ` Paolo Bonzini
2019-03-11 16:58 ` Xiaoyao Li
2019-03-04 21:55 ` [PATCH v4 00/17] x86/split_lock: Enable #AC exception for split locked accesses Konrad Rzeszutek Wilk
2019-03-05 0:06 ` Fenghua Yu
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