linux-kernel - Re: [PATCH 5/6] treewide: use kv[mz]alloc* rather than opencoded variants

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Message-ID: <20170114084912.GB9962@dhcp22.suse.cz>
Date:   Sat, 14 Jan 2017 09:49:13 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/6] treewide: use kv[mz]alloc* rather than opencoded
 variants

On Sat 14-01-17 12:01:50, Tetsuo Handa wrote:
> On 2017/01/13 2:29, Michal Hocko wrote:
> > Ilya has noticed that I've screwed up some k[zc]alloc conversions and
> > didn't use the kvzalloc. This is an updated patch with some acks
> > collected on the way
> > ---
> > From a7b89c6d0a3c685045e37740c8f97b065f37e0a4 Mon Sep 17 00:00:00 2001
> > From: Michal Hocko <mhocko@...e.com>
> > Date: Wed, 4 Jan 2017 13:30:32 +0100
> > Subject: [PATCH] treewide: use kv[mz]alloc* rather than opencoded variants
> > 
> > There are many code paths opencoding kvmalloc. Let's use the helper
> > instead. The main difference to kvmalloc is that those users are usually
> > not considering all the aspects of the memory allocator. E.g. allocation
> > requests < 64kB are basically never failing and invoke OOM killer to
> 
> Isn't this "requests <= 32kB" because allocation requests for 33kB will be
> rounded up to 64kB?

Yes

> Same for "smaller than 64kB" in PATCH 6/6. But strictly speaking, isn't
> it bogus to refer actual size because PAGE_SIZE is not always 4096?

This is just an example and I didn't want to pull
PAGE_ALLOC_COSTLY_ORDER here. So I've instead fixed the wording to:
"
E.g. allocation requests <= 32kB (with 4kB pages) are basically never
failing and invoke OOM killer to satisfy the allocation.
"
-- 
Michal Hocko
SUSE Labs