From: "Ma, Yu" <yu.ma@intel.com>
To: "Liam.Howlett@Oracle.com" <Liam.Howlett@Oracle.com>,
Dennis Zhou <dennis@kernel.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>
Cc: "Williams, Dan J" <dan.j.williams@intel.com>,
"Hansen, Dave" <dave.hansen@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"Zhu, Lipeng" <lipeng.zhu@intel.com>,
"Deng, Pan" <pan.deng@intel.com>,
"shakeelb@google.com" <shakeelb@google.com>,
"Li, Tianyou" <tianyou.li@intel.com>,
"Chen, Tim C" <tim.c.chen@intel.com>,
"tim.c.chen@linux.intel.com" <tim.c.chen@linux.intel.com>
Subject: RE: [PATCH v2] percpu-internal/pcpu_chunk: Re-layout pcpu_chunk structure to reduce false sharing
Date: Wed, 7 Jun 2023 15:02:32 +0000 [thread overview]
Message-ID: <SN7PR11MB7590D5959AF7179137A314FEE153A@SN7PR11MB7590.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20230607145009.58899-1-yu.ma@intel.com>
Thanks Liam and Dennis for review, this is updated patch with comment around:
> 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 | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/mm/percpu-internal.h b/mm/percpu-internal.h index
> f9847c131998..ecc7be1ec876 100644
> --- a/mm/percpu-internal.h
> +++ b/mm/percpu-internal.h
> @@ -41,10 +41,16 @@ 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 */
> +
> + /*
> + * To reduce false sharing, current layout is optimized to make sure
> + * base_addr locate in the different cacheline with free_bytes and
> + * chunk_md.
> + */
> 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 prev parent reply other threads:[~2023-06-07 15:05 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-06 12:54 [PATCH] percpu-internal/pcpu_chunk: Re-layout pcpu_chunk structure to reduce false sharing Yu Ma
2023-06-06 19:21 ` 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 [this message]
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=SN7PR11MB7590D5959AF7179137A314FEE153A@SN7PR11MB7590.namprd11.prod.outlook.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=dennis@kernel.org \
--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).