linux-kernel - Re: [v6 15/15] mm: debug for raw alloctor

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Message-ID: <20170814115000.GJ19063@dhcp22.suse.cz>
Date:   Mon, 14 Aug 2017 13:50:01 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Pasha Tatashin <pasha.tatashin@...cle.com>
Cc:     linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        x86@...nel.org, kasan-dev@...glegroups.com, borntraeger@...ibm.com,
        heiko.carstens@...ibm.com, davem@...emloft.net,
        willy@...radead.org, ard.biesheuvel@...aro.org,
        will.deacon@....com, catalin.marinas@....com, sam@...nborg.org
Subject: Re: [v6 15/15] mm: debug for raw alloctor

On Fri 11-08-17 12:18:24, Pasha Tatashin wrote:
> >>When CONFIG_DEBUG_VM is enabled, this patch sets all the memory that is
> >>returned by memblock_virt_alloc_try_nid_raw() to ones to ensure that no
> >>places excpect zeroed memory.
> >
> >Please fold this into the patch which introduces
> >memblock_virt_alloc_try_nid_raw.
> 
> OK
> 
>  I am not sure CONFIG_DEBUG_VM is the
> >best config because that tends to be enabled quite often. Maybe
> >CONFIG_MEMBLOCK_DEBUG? Or even make it kernel command line parameter?
> >
> 
> Initially, I did not want to make it CONFIG_MEMBLOCK_DEBUG because we really
> benefit from this debugging code when VM debug is enabled, and especially
> struct page debugging asserts which also depend on CONFIG_DEBUG_VM.
> 
> However, now thinking about it, I will change it to CONFIG_MEMBLOCK_DEBUG,
> and let users decide what other debugging configs need to be enabled, as
> this is also OK.

Actually the more I think about it the more I am convinced that a kernel
boot parameter would be better because it doesn't need the kernel to be
recompiled and it is a single branch in not so hot path.
-- 
Michal Hocko
SUSE Labs