linux-kernel - Re: [PATCH v3] efi: take size of partition entry from GPT header

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Message-ID: <CAJC2YLb+YM11jzWLVTea6gEa=Ou2rdJC1rY9TbK+yOpAfyWFyg@mail.gmail.com>
Date:   Thu, 13 Sep 2018 22:44:56 +0300
From:   Eugene Korenevsky <ekorenevsky@...il.com>
To:     David.Laight@...lab.com
Cc:     Davidlohr Bueso <dave@...olabs.net>, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [PATCH v3] efi: take size of partition entry from GPT header

> > Please rearrange this like:
> >
> >        for (i = 0; i < le32_to_cpu(gpt->num_partition_entries) &&
> >                             i < state->limit-1; i++)
>
> Better still cache le32_to_cpu(gpt->num_partition_entries) to a local
> so that it only has to be calculated once (even if it gets spilled
> to the stack).
> It can be bounded by state->limit-1 at the same time.

This is block I/O, slow path. No need for such micro optimizations here.
GCC is capable to do such optimizations automatically, and it does as
I can see from disassembly.
Anyway this would be a subject for another patch.

-- 
Eugene