From: Robin Murphy <robin.murphy@arm.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Eric Dumazet <edumazet@google.com>,
Christoph Hellwig <hch@lst.de>, Joerg Roedel <jroedel@suse.de>,
Linux IOMMU <iommu@lists.linux-foundation.org>,
Eric Dumazet <eric.dumazet@gmail.com>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] dma-debug: dynamic allocation of hash table
Date: Fri, 31 Jan 2020 11:33:48 +0000 [thread overview]
Message-ID: <a305bd1f-8142-6557-4228-aae10c5114e1@arm.com> (raw)
In-Reply-To: <CAMuHMdVSyD62nvRmN-v6CbJ2UyqH=d7xdVeCD8_X5us+mvCXUQ@mail.gmail.com>
On 2020-01-31 9:06 am, Geert Uytterhoeven wrote:
> Hi Robin,
>
> On Fri, Jan 31, 2020 at 12:46 AM Robin Murphy <robin.murphy@arm.com> wrote:
>> On 2020-01-30 7:10 pm, Eric Dumazet via iommu wrote:
>>> Increasing the size of dma_entry_hash size by 327680 bytes
>>> has reached some bootloaders limitations.
>>
>> [ That might warrant some further explanation - I don't quite follow how
>> this would relate to a bootloader specifically :/ ]
>
> Increasing the size of a static array increases kernel size.
> Some (all? ;-) bootloaders have limitations on the maximum size of a
> kernel image they can boot (usually something critical gets overwritten
> when handling a too large image). While boot loaders can be fixed and
> upgraded, this is usually much more cumbersome than updating the
> kernel.
Ah, OK - I'm all too familiar with bootloaders having image size limits,
but I'm also used to implicitly-initialised statics being collected into
a runtime-initialised .bss section, so I hadn't realised that there
might still be platforms where that space is actually allocated in the
image at link-time.
> Besides, a static array always consumes valuable unswapable memory,
> even when the feature would not be used (e.g. disabled by a command
> line option).
Indeed, and that alone might have been a reasonable rationale for the
patch - I was merely querying the wording of the commit message, not its
intent :)
Thanks,
Robin.
prev parent reply other threads:[~2020-01-31 11:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-30 19:10 [PATCH] dma-debug: dynamic allocation of hash table Eric Dumazet
2020-01-30 23:46 ` Robin Murphy
2020-01-31 0:17 ` Eric Dumazet
2020-01-31 12:30 ` Robin Murphy
2020-01-31 14:42 ` Eric Dumazet
2020-01-31 17:43 ` Robin Murphy
2020-01-31 17:46 ` Eric Dumazet
2020-02-01 0:06 ` Robin Murphy
2020-01-31 9:06 ` Geert Uytterhoeven
2020-01-31 11:33 ` Robin Murphy [this message]
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