From: Andrew Morton <akpm@linux-foundation.org>
To: Chintan Pandya <cpandya@codeaurora.org>
Cc: David Rientjes <rientjes@google.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v2] mm: BUG when __kmap_atomic_idx equals KM_TYPE_NR
Date: Thu, 31 Jul 2014 15:45:40 -0700 [thread overview]
Message-ID: <20140731154540.441ab79ff32ae5c10f64bcbd@linux-foundation.org> (raw)
In-Reply-To: <53DA0C5A.3010409@codeaurora.org>
On Thu, 31 Jul 2014 14:58:58 +0530 Chintan Pandya <cpandya@codeaurora.org> wrote:
> >
> > I think Andrew's comment earlier was referring to the changelog only and
> > not the patch, which looked correct.
>
> I think Andrew asked for a BUG case details also to justify the
> overhead. But we have never encountered that BUG case. Present patch is
> only logical fix to the code. However, in the fast path, if such
> overhead is allowed, I can move BUG_ON out of any debug configs.
> Otherwise, as per Andrew's suggestion, I will convert DEBUG_HIGHMEM into
> DEBUG_VM which is used more frequently.
The v1 patch added a small amount of overhead to kmap_atomic() for what
is evidently a very small benefit.
Yes, I suggest we remove CONFIG_DEBUG_HIGHMEM from the kernel entirely
and switch all CONFIG_DEBUG_HIGHMEM sites to use CONFIG_DEBUG_VM. That way
the BUG_ON which you believe is useful will be tested by more people
more often.
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next prev parent reply other threads:[~2014-07-31 22:45 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-31 6:24 Chintan Pandya
2014-07-31 7:02 ` David Rientjes
2014-07-31 9:28 ` Chintan Pandya
2014-07-31 22:45 ` Andrew Morton [this message]
2014-08-04 9:25 ` Chintan Pandya
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