From: Yu Ma <yu.ma@intel.com>
To: akpm@linux-foundation.org, tim.c.chen@intel.com
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
dave.hansen@intel.com, dan.j.williams@intel.com,
shakeelb@google.com, Liam.Howlett@Oracle.com, pan.deng@intel.com,
tianyou.li@intel.com, lipeng.zhu@intel.com,
tim.c.chen@linux.intel.com, yu.ma@intel.com
Subject: [PATCH] percpu-internal/pcpu_chunk: Re-layout pcpu_chunk structure to reduce false sharing
Date: Tue, 6 Jun 2023 08:54:04 -0400 [thread overview]
Message-ID: <20230606125404.95256-1-yu.ma@intel.com> (raw)
When running UnixBench/Execl throughput case, false sharing is observed
due to frequent read on base_addr and write on free_bytes, chunk_md.
UnixBench/Execl represents a class of workload where bash scripts
are spawned frequently to do some short jobs. It will do system call on
execl frequently, and execl will call mm_init to initialize mm_struct
of the process. mm_init will call __percpu_counter_init for
percpu_counters initialization. Then pcpu_alloc is called to read
the base_addr of pcpu_chunk for memory allocation. Inside pcpu_alloc,
it will call pcpu_alloc_area to allocate memory from a specified chunk.
This function will update "free_bytes" and "chunk_md" to record the
rest free bytes and other meta data for this chunk. Correspondingly,
pcpu_free_area will also update these 2 members when free memory.
Call trace from perf is as below:
+ 57.15% 0.01% execl [kernel.kallsyms] [k] __percpu_counter_init
+ 57.13% 0.91% execl [kernel.kallsyms] [k] pcpu_alloc
- 55.27% 54.51% execl [kernel.kallsyms] [k] osq_lock
- 53.54% 0x654278696e552f34
main
__execve
entry_SYSCALL_64_after_hwframe
do_syscall_64
__x64_sys_execve
do_execveat_common.isra.47
alloc_bprm
mm_init
__percpu_counter_init
pcpu_alloc
- __mutex_lock.isra.17
In current pcpu_chunk layout, ‘base_addr’ is in the same cache line
with ‘free_bytes’ and ‘chunk_md’, and ‘base_addr’ is at the
last 8 bytes. This patch moves ‘bound_map’ up to ‘base_addr’,
to let ‘base_addr’ locate in a new cacheline.
With this change, on Intel Sapphire Rapids 112C/224T platform,
based on v6.4-rc4, the 160 parallel score improves by 24%.
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Yu Ma <yu.ma@intel.com>
---
mm/percpu-internal.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/percpu-internal.h b/mm/percpu-internal.h
index f9847c131998..981eeb2ad0a9 100644
--- a/mm/percpu-internal.h
+++ b/mm/percpu-internal.h
@@ -41,10 +41,10 @@ struct pcpu_chunk {
struct list_head list; /* linked to pcpu_slot lists */
int free_bytes; /* free bytes in the chunk */
struct pcpu_block_md chunk_md;
+ unsigned long *bound_map; /* boundary map */
void *base_addr; /* base address of this chunk */
unsigned long *alloc_map; /* allocation map */
- unsigned long *bound_map; /* boundary map */
struct pcpu_block_md *md_blocks; /* metadata blocks */
void *data; /* chunk data */
--
2.39.3
next reply other threads:[~2023-06-06 12:27 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-06 12:54 Yu Ma [this message]
2023-06-06 19:21 ` [PATCH] percpu-internal/pcpu_chunk: Re-layout pcpu_chunk structure to reduce false sharing Liam R. Howlett
2023-06-06 21:25 ` Dennis Zhou
2023-06-07 12:50 ` Ma, Yu
2023-06-07 14:50 ` [PATCH v2] " Yu Ma
2023-06-07 15:02 ` Ma, Yu
2023-06-09 18:20 ` Dennis Zhou
2023-06-10 0:12 ` Ma, Yu
2023-06-10 3:07 ` [PATCH v3] " Yu Ma
2023-06-12 21:43 ` Andrew Morton
2023-06-12 21:55 ` Dennis Zhou
2023-06-13 17:41 ` Ma, Yu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20230606125404.95256-1-yu.ma@intel.com \
--to=yu.ma@intel.com \
--cc=Liam.Howlett@Oracle.com \
--cc=akpm@linux-foundation.org \
--cc=dan.j.williams@intel.com \
--cc=dave.hansen@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lipeng.zhu@intel.com \
--cc=pan.deng@intel.com \
--cc=shakeelb@google.com \
--cc=tianyou.li@intel.com \
--cc=tim.c.chen@intel.com \
--cc=tim.c.chen@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).