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From: Aaron Lu <aaron.lu@intel.com>
To: Song Liu <song@kernel.org>
Cc: <linux-kernel@vger.kernel.org>, <bpf@vger.kernel.org>,
	<linux-mm@kvack.org>, <ast@kernel.org>, <daniel@iogearbox.net>,
	<peterz@infradead.org>, <mcgrof@kernel.org>,
	<torvalds@linux-foundation.org>, <rick.p.edgecombe@intel.com>,
	<kernel-team@fb.com>
Subject: Re: [PATCH v4 bpf-next 0/8] bpf_prog_pack followup
Date: Mon, 20 Jun 2022 19:11:45 +0800	[thread overview]
Message-ID: <YrBV8darrlmUnrHR@ziqianlu-Dell-Optiplex7000> (raw)
In-Reply-To: <20220520235758.1858153-1-song@kernel.org>

Hi Song,

On Fri, May 20, 2022 at 04:57:50PM -0700, Song Liu wrote:

... ...

> The primary goal of bpf_prog_pack is to reduce iTLB miss rate and reduce
> direct memory mapping fragmentation. This leads to non-trivial performance
> improvements.
>
> For our web service production benchmark, bpf_prog_pack on 4kB pages
> gives 0.5% to 0.7% more throughput than not using bpf_prog_pack.
> bpf_prog_pack on 2MB pages 0.6% to 0.9% more throughput than not using
> bpf_prog_pack. Note that 0.5% is a huge improvement for our fleet. I
> believe this is also significant for other companies with many thousand
> servers.
>

I'm evaluationg performance impact due to direct memory mapping
fragmentation and seeing the above, I wonder: is the performance improve
mostly due to prog pack and hugepage instead of less direct mapping
fragmentation?

I can understand that when progs are packed together, iTLB miss rate will
be reduced and thus, performance can be improved. But I don't see
immediately how direct mapping fragmentation can impact performance since
the bpf code are running from the module alias addresses, not the direct
mapping addresses IIUC?

I appreciate it if you can shed some light on performance impact direct
mapping fragmentation can cause, thanks.

  parent reply	other threads:[~2022-06-20 11:14 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-20 23:57 [PATCH v4 bpf-next 0/8] bpf_prog_pack followup Song Liu
2022-05-20 23:57 ` [PATCH v4 bpf-next 1/8] bpf: fill new bpf_prog_pack with illegal instructions Song Liu
2022-05-20 23:57 ` [PATCH v4 bpf-next 2/8] x86/alternative: introduce text_poke_set Song Liu
2022-05-20 23:57 ` [PATCH v4 bpf-next 3/8] bpf: introduce bpf_arch_text_invalidate for bpf_prog_pack Song Liu
2022-05-24  7:20   ` Mike Rapoport
2022-05-20 23:57 ` [PATCH v4 bpf-next 4/8] module: introduce module_alloc_huge Song Liu
2022-05-20 23:57 ` [PATCH v4 bpf-next 5/8] bpf: use module_alloc_huge for bpf_prog_pack Song Liu
2022-05-24  7:22   ` Mike Rapoport
2022-05-24 16:42     ` Edgecombe, Rick P
2022-06-17 23:05   ` Edgecombe, Rick P
2022-05-20 23:57 ` [PATCH v4 bpf-next 6/8] vmalloc: WARN for set_vm_flush_reset_perms() on huge pages Song Liu
2022-05-20 23:57 ` [PATCH v4 bpf-next 7/8] vmalloc: introduce huge_vmalloc_supported Song Liu
2022-05-20 23:57 ` [PATCH v4 bpf-next 8/8] bpf: simplify select_bpf_prog_pack_size Song Liu
2022-05-23 21:20 ` [PATCH v4 bpf-next 0/8] bpf_prog_pack followup patchwork-bot+netdevbpf
2022-06-20 11:11 ` Aaron Lu [this message]
2022-06-20 16:03   ` Song Liu
2022-06-21  1:31     ` Aaron Lu
2022-06-21  2:51       ` Song Liu
2022-06-21  3:25         ` Aaron Lu
2022-06-20 18:31   ` Luis Chamberlain
2022-06-21  1:45     ` Aaron Lu

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