From: Shaokun Zhang <zhangshaokun@hisilicon.com>
To: <linux-fsdevel@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Cc: Shaokun Zhang <zhangshaokun@hisilicon.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Boqun Feng <boqun.feng@gmail.com>, Yuqi Jin <jinyuqi@huawei.com>
Subject: [PATCH RESEND] fs: Move @f_count to different cacheline with @f_mode
Date: Wed, 24 Jun 2020 16:32:28 +0800 [thread overview]
Message-ID: <1592987548-8653-1-git-send-email-zhangshaokun@hisilicon.com> (raw)
get_file_rcu_many, which is called by __fget_files, has used
atomic_try_cmpxchg now and it can reduce the access number of the global
variable to improve the performance of atomic instruction compared with
atomic_cmpxchg.
__fget_files does check the @f_mode with mask variable and will do some
atomic operations on @f_count, but both are on the same cacheline.
Many CPU cores do file access and it will cause much conflicts on @f_count.
If we could make the two members into different cachelines, it shall relax
the siutations.
We have tested this on ARM64 and X86, the result is as follows:
Syscall of unixbench has been run on Huawei Kunpeng920 with this patch:
24 x System Call Overhead 1
System Call Overhead 3160841.4 lps (10.0 s, 1 samples)
System Benchmarks Partial Index BASELINE RESULT INDEX
System Call Overhead 15000.0 3160841.4 2107.2
========
System Benchmarks Index Score (Partial Only) 2107.2
Without this patch:
24 x System Call Overhead 1
System Call Overhead 2222456.0 lps (10.0 s, 1 samples)
System Benchmarks Partial Index BASELINE RESULT INDEX
System Call Overhead 15000.0 2222456.0 1481.6
========
System Benchmarks Index Score (Partial Only) 1481.6
And on Intel 6248 platform with this patch:
40 CPUs in system; running 24 parallel copies of tests
System Call Overhead 4288509.1 lps (10.0 s, 1 samples)
System Benchmarks Partial Index BASELINE RESULT INDEX
System Call Overhead 15000.0 4288509.1 2859.0
========
System Benchmarks Index Score (Partial Only) 2859.0
Without this patch:
40 CPUs in system; running 24 parallel copies of tests
System Call Overhead 3666313.0 lps (10.0 s, 1 samples)
System Benchmarks Partial Index BASELINE RESULT INDEX
System Call Overhead 15000.0 3666313.0 2444.2
========
System Benchmarks Index Score (Partial Only) 2444.2
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Yuqi Jin <jinyuqi@huawei.com>
Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
---
include/linux/fs.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3f881a892ea7..0faeab5622fb 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -955,7 +955,6 @@ struct file {
*/
spinlock_t f_lock;
enum rw_hint f_write_hint;
- atomic_long_t f_count;
unsigned int f_flags;
fmode_t f_mode;
struct mutex f_pos_lock;
@@ -979,6 +978,7 @@ struct file {
struct address_space *f_mapping;
errseq_t f_wb_err;
errseq_t f_sb_err; /* for syncfs */
+ atomic_long_t f_count;
} __randomize_layout
__attribute__((aligned(4))); /* lest something weird decides that 2 is OK */
--
2.7.4
next reply other threads:[~2020-06-24 8:34 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-24 8:32 Shaokun Zhang [this message]
2020-07-08 7:23 ` [fs] 936e92b615: unixbench.score 32.3% improvement kernel test robot
2020-07-13 8:49 ` Shaokun Zhang
2020-08-21 16:02 ` [PATCH RESEND] fs: Move @f_count to different cacheline with @f_mode Will Deacon
2020-08-26 7:24 ` Shaokun Zhang
2020-08-26 8:24 ` Aleksa Sarai
2020-08-27 8:27 ` Shaokun Zhang
2020-09-08 11:37 ` Jan Kara
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