From: Andi Kleen <andi.kleen@intel.com>
To: Feng Tang <feng.tang@intel.com>
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>,
Qian Cai <cai@lca.pw>,
tim.c.chen@intel.com, dave.hansen@intel.com,
ying.huang@intel.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 2/4] mm/util.c: make vm_memory_committed() more accurate
Date: Wed, 3 Jun 2020 07:28:53 -0700 [thread overview]
Message-ID: <20200603142853.GE621576@tassilo.jf.intel.com> (raw)
In-Reply-To: <1590714370-67182-3-git-send-email-feng.tang@intel.com>
> Its time cost is about 800 nanoseconds on a 2C/4T platform and
> 2~3 microseconds on a 2S/36C/72T server in normal case, and in
> worst case where vm_committed_as's spinlock is under severe
> contention, it costs 30~40 microseconds for the 2S/36C/72T sever,
This will be likely 40-80us on larger systems, although the overhead
is often non linear so it might get worse.
> which should be fine for its only two users: /proc/meminfo and
> HyperV balloon driver's status trace per second.
There are some setups who do frequent sampling of /proc/meminfo
in the background. Increased overhead could be a problem for them.
But not proposing a change now. If someone complains have to
revisit I guess, perhaps adding a rate limit of some sort.
-Andi
next prev parent reply other threads:[~2020-06-03 14:28 UTC|newest]
Thread overview: 12+ 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 [this message]
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
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
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