Re: [PATCH] Revert "lib: sparse: Make CHUNK_TYPE_RAW buffer aligned"

Sean Anderson
2022-11-21T15:10:21Z

On 11/21/22 09:50, Gary Bisson wrote:
> Hi,
>
> On Fri, Nov 18, 2022 at 10:36:58AM -0500, Sean Anderson wrote:
>> On 11/18/22 07:13, Gary Bisson wrote:
>> > This reverts commit 62649165cb02ab95b57360bb362886935f524f26.
>> >
>> > The patch decreased the write performance quite a bit.
>> > Here is an example on an i.MX 8M Quad platform.
>> > - Before the revert:
>> > Sending sparse 'vendor' 1/2 (516436 KB) OKAY [ 5.113s]
>> > Writing 'vendor' OKAY [128.335s]
>> > Sending sparse 'vendor' 2/2 (76100 KB) OKAY [ 0.802s]
>> > Writing 'vendor' OKAY [ 27.902s]
>> > - After the revert:
>> > Sending sparse 'vendor' 1/2 (516436 KB) OKAY [ 5.310s]
>> > Writing 'vendor' OKAY [ 18.041s]
>> > Sending sparse 'vendor' 2/2 (76100 KB) OKAY [ 1.244s]
>> > Writing 'vendor' OKAY [ 2.663s]
>> >
>> > Considering that the patch only moves buffer around to avoid a warning
>> > message about misaligned buffers, let's keep the best performances.
>>
>> So what is the point of this warning?
>
> Well the warning does say something true that the cache operation is not
> aligned. Better ask Simon as he's the one who changed the print from a
> debug to warn_non_spl one:
> bcc53bf0958 arm: Show cache warnings in U-Boot proper only
>
> BTW, in my case I couldn't see the misaligned messages, yet I saw the
> performance hit described above.

Maybe it is better to keep this as a Kconfig? Some arches may support
unaligned access but others may not. I wonder if we have something like
this already.

--Seam