From: Dan Smith <danms@us.ibm.com>
To: David Rientjes <rientjes@google.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Ensure that walk_page_range()'s start and end are page-aligned
Date: Tue, 14 Feb 2012 06:59:51 -0800 [thread overview]
Message-ID: <87pqdh1mvs.fsf@caffeine.danplanet.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1202131350500.17296@chino.kir.corp.google.com> (David Rientjes's message of "Mon, 13 Feb 2012 13:55:31 -0800 (PST)")
DR> That's not a precedent, there's a big difference between the
DR> performance of gup_fast(), where we can't spare an additional
DR> compare and branch, and walk_page_range(). VM_BUG_ON() is typically
DR> used in situations where a debug kernel has been built, including
DR> CONFIG_DEBUG_VM, and the check helps to isolate a problem that would
DR> be otherwise difficult to find.
Okay, fair enough. I was trying to stay in line with the other
conventions, knowing that the check would only be done with
CONFIG_DEBUG_VM enabled.
I'd rather just make it always do the check in walk_page_range(). Does
that sound reasonable?
--
Dan Smith
IBM Linux Technology Center
email: danms@us.ibm.com
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WARNING: multiple messages have this Message-ID (diff)
From: Dan Smith <danms@us.ibm.com>
To: David Rientjes <rientjes@google.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Ensure that walk_page_range()'s start and end are page-aligned
Date: Tue, 14 Feb 2012 06:59:51 -0800 [thread overview]
Message-ID: <87pqdh1mvs.fsf@caffeine.danplanet.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1202131350500.17296@chino.kir.corp.google.com> (David Rientjes's message of "Mon, 13 Feb 2012 13:55:31 -0800 (PST)")
DR> That's not a precedent, there's a big difference between the
DR> performance of gup_fast(), where we can't spare an additional
DR> compare and branch, and walk_page_range(). VM_BUG_ON() is typically
DR> used in situations where a debug kernel has been built, including
DR> CONFIG_DEBUG_VM, and the check helps to isolate a problem that would
DR> be otherwise difficult to find.
Okay, fair enough. I was trying to stay in line with the other
conventions, knowing that the check would only be done with
CONFIG_DEBUG_VM enabled.
I'd rather just make it always do the check in walk_page_range(). Does
that sound reasonable?
--
Dan Smith
IBM Linux Technology Center
email: danms@us.ibm.com
next prev parent reply other threads:[~2012-02-14 14:59 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-10 19:39 [PATCH] Ensure that walk_page_range()'s start and end are page-aligned Dan Smith
2012-02-10 19:39 ` Dan Smith
2012-02-10 19:45 ` Michal Nazarewicz
2012-02-10 19:45 ` Michal Nazarewicz
2012-02-10 19:57 ` Dan Smith
2012-02-10 19:57 ` Dan Smith
2012-02-10 20:13 ` Michal Nazarewicz
2012-02-10 20:13 ` Michal Nazarewicz
2012-02-13 10:12 ` David Rientjes
2012-02-13 10:12 ` David Rientjes
2012-02-13 14:52 ` Dan Smith
2012-02-13 14:52 ` Dan Smith
2012-02-13 21:55 ` David Rientjes
2012-02-13 21:55 ` David Rientjes
2012-02-14 14:59 ` Dan Smith [this message]
2012-02-14 14:59 ` Dan Smith
2012-02-14 21:04 ` David Rientjes
2012-02-14 21:04 ` David Rientjes
2012-02-15 14:39 ` Dan Smith
2012-02-15 14:39 ` Dan Smith
2012-02-24 19:19 ` Dan Smith
2012-02-24 19:19 ` Dan Smith
2012-02-24 20:55 ` Andrew Morton
2012-02-24 20:55 ` Andrew Morton
2012-02-24 21:03 ` Dan Smith
2012-02-24 21:03 ` Dan Smith
-- strict thread matches above, loose matches on Subject: below --
2012-02-10 15:53 Dan Smith
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