From: Feng Tang <feng.tang@intel.com>
To: Qian Cai <cai@lca.pw>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Matthew Wilcox <willy@infradead.org>,
Mel Gorman <mgorman@suse.de>, Kees Cook <keescook@chromium.org>,
andi.kleen@intel.com, tim.c.chen@intel.com,
dave.hansen@intel.com, ying.huang@intel.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
Konstantin Khlebnikov <koct9i@gmail.com>
Subject: Re: [PATCH v4 3/4] mm/util.c: remove the VM_WARN_ONCE for vm_committed_as underflow check
Date: Fri, 29 May 2020 13:37:13 +0800 [thread overview]
Message-ID: <20200529053713.GH93879@shbuild999.sh.intel.com> (raw)
In-Reply-To: <20200529024928.GA4566@lca.pw>
On Thu, May 28, 2020 at 10:49:28PM -0400, Qian Cai wrote:
> On Fri, May 29, 2020 at 09:06:09AM +0800, Feng Tang wrote:
> > As is explained by Michal Hocko:
> >
> > : Looking at the history, this has been added by 82f71ae4a2b8
> > : ("mm: catch memory commitment underflow") to have a safety check
> > : for issues which have been fixed. There doesn't seem to be any bug
> > : reports mentioning this splat since then so it is likely just
> > : spending cycles for a hot path (yes many people run with DEBUG_VM)
> > : without a strong reason.
>
> Hmm, it looks like the warning is still useful to catch issues in,
>
> https://lore.kernel.org/linux-mm/20140624201606.18273.44270.stgit@zurg
> https://lore.kernel.org/linux-mm/54BB9A32.7080703@oracle.com/
>
> After read the whole discussion in that thread, I actually disagree with
> Michal. In order to get ride of this existing warning, it is rather
> someone needs a strong reason that could prove the performance hit is
> noticeable with some data.
One problem with current check is percpu_counter_read(&vm_committed_as)
is not accurate, and percpu_counter_sum() is way too heavy.
Thanks,
Feng
next prev parent reply other threads:[~2020-05-29 5:37 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-29 1:06 [PATCH v4 0/4] make vm_committed_as_batch aware of vm overcommit policy Feng Tang
2020-05-29 1:06 ` [PATCH v4 1/4] proc/meminfo: avoid open coded reading of vm_committed_as Feng Tang
2020-05-29 1:06 ` [PATCH v4 2/4] mm/util.c: make vm_memory_committed() more accurate Feng Tang
2020-06-03 13:35 ` Michal Hocko
2020-06-03 14:28 ` Andi Kleen
2020-06-04 1:38 ` Feng Tang
2020-05-29 1:06 ` [PATCH v4 3/4] mm/util.c: remove the VM_WARN_ONCE for vm_committed_as underflow check Feng Tang
2020-05-29 2:49 ` Qian Cai
2020-05-29 5:37 ` Feng Tang [this message]
2020-06-02 3:37 ` Feng Tang
2020-05-29 1:06 ` [PATCH v4 4/4] mm: adjust vm_committed_as_batch according to vm overcommit policy Feng Tang
2020-06-03 13:38 ` Michal Hocko
2020-06-02 4:02 [PATCH v4 3/4] mm/util.c: remove the VM_WARN_ONCE for vm_committed_as underflow check Qian Cai
2020-06-03 9:48 ` Feng Tang
2020-06-03 11:51 ` Qian Cai
2020-06-03 13:36 ` Michal Hocko
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