linux-kernel - Re: [PATCH net-next v2] lib: Allow for the DIM library to be modular

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Date: Wed, 8 May 2024 11:17:08 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Florian Fainelli <florian.fainelli@...adcom.com>
CC: <netdev@...r.kernel.org>, <kuba@...nel.org>, <jgg@...dia.com>,
	<leonro@...dia.com>, <horms@...nel.org>, Andrew Morton
	<akpm@...ux-foundation.org>, Tal Gilboa <talgi@...dia.com>, "open
 list:LIBRARY CODE" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v2] lib: Allow for the DIM library to be modular

From: Florian Fainelli <florian.fainelli@...adcom.com>
Date: Tue, 7 May 2024 10:08:19 -0700

> On 5/7/24 06:13, Alexander Lobakin wrote:
>> From: Florian Fainelli <florian.fainelli@...adcom.com>
>> Date: Mon,  6 May 2024 10:50:40 -0700
>>
>>> Allow the Dynamic Interrupt Moderation (DIM) library to be built as a
>>> module. This is particularly useful in an Android GKI (Google Kernel
>>> Image) configuration where everything is built as a module, including
>>> Ethernet controller drivers. Having to build DIMLIB into the kernel
>>> image with potentially no user is wasteful.
>>
>> Some bloat-o-meter -c vmlinux.{before,after} would be good to have here.
>> The library is small, but I personally would like to see it modular.
> 
> ./scripts/bloat-o-meter vmlinux vmlinux.after
> add/remove: 1/16 grow/shrink: 0/0 up/down: 8/-1980 (-1972)
> Function                                     old     new   delta
> e843419@...0_00005048_4014                     -       8      +8
> e843419@...3_000055c6_5944                     8       -      -8
> dim_park_on_top                                8       -      -8
> dim_park_tired                                16       -     -16
> net_dim_get_def_tx_moderation                 24       -     -24
> net_dim_get_def_rx_moderation                 24       -     -24
> dim_turn                                      52       -     -52
> net_dim_get_rx_moderation                     60       -     -60
> net_dim_get_tx_moderation                     64       -     -64
> tx_profile                                    80       -     -80
> rx_profile                                    80       -     -80
> dim_on_top                                    84       -     -84
> net_dim_step                                 132       -    -132
> dim_calc_stats                               172       -    -172
> net_dim_stats_compare                        176       -    -176
> net_dim                                      464       -    -464
> rdma_dim                                     536       -    -536
> Total: Before=12668884, After=12666912, chg -0.02%
> 
> This is on arm64 FWIW.

-2 Kb sounds reasonable I'd say. This doesn't even require adding new
exports, nice.

> 
>>
>>>
>>> Signed-off-by: Florian Fainelli <florian.fainelli@...adcom.com>
>>
>> Reviewed-by: Alexander Lobakin <aleksander.lobakin@...el.com>
>>
>>> ---
>>> Changes in v2:
>>>
>>> - Added MODULE_DESCRIPTION()
>>>
>>>   lib/Kconfig      | 2 +-
>>>   lib/dim/Makefile | 4 ++--
>>>   lib/dim/dim.c    | 3 +++
>>>   3 files changed, 6 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/lib/Kconfig b/lib/Kconfig
>>> index 4557bb8a5256..d33a268bc256 100644
>>> --- a/lib/Kconfig
>>> +++ b/lib/Kconfig
>>> @@ -628,7 +628,7 @@ config SIGNATURE
>>>         Implementation is done using GnuPG MPI library
>>>     config DIMLIB
>>> -    bool
>>> +    tristate
>>>       help
>>>         Dynamic Interrupt Moderation library.
>>>         Implements an algorithm for dynamically changing CQ
>>> moderation values
>>> diff --git a/lib/dim/Makefile b/lib/dim/Makefile
>>> index 1d6858a108cb..c4cc4026c451 100644
>>> --- a/lib/dim/Makefile
>>> +++ b/lib/dim/Makefile
>>> @@ -2,6 +2,6 @@
>>>   # DIM Dynamic Interrupt Moderation library
>>>   #
>>>   -obj-$(CONFIG_DIMLIB) += dim.o
>>> +obj-$(CONFIG_DIMLIB) += dimlib.o
>>
>> I guess you renamed it due to that there's already a module named 'dim'?
> 
> This is required to avoid the follow recursive dependency:
> 
> make[4]: Circular lib/dim/dim.o <- lib/dim/dim.o dependency dropped.

Aaah I see!

Thanks,
Olek