From: Peter Zijlstra <peterz@infradead.org>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: kernel test robot <xiaolong.ye@intel.com>,
Ingo Molnar <mingo@kernel.org>, Juergen Gross <jgross@suse.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Andy Lutomirski <luto@amacapital.net>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Jork Loeser <Jork.Loeser@microsoft.com>,
KY Srinivasan <kys@microsoft.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
lkp@01.org
Subject: Re: [lkp-robot] [x86/mm] 9e52fc2b50: will-it-scale.per_thread_ops -16% regression
Date: Fri, 29 Sep 2017 15:13:29 +0200 [thread overview]
Message-ID: <20170929131329.tekd6a7yfrkm7lwl@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <87d169zo9o.fsf@vitty.brq.redhat.com>
On Fri, Sep 29, 2017 at 02:24:03PM +0200, Vitaly Kuznetsov wrote:
> 1) In case the system is under extreme memory pressure and
> __get_free_page() is failing in tlb_remove_table() we'll be doing
> smp_call_function() for _each_ call (avoiding batching). We may want to
> have a pre-allocated pool.
MMU_GATHER_BUNDLE should avoid it being for _every_ call.
Also, note that tlb_gather is preemptible, so pre-alloc is 'difficult'
and you will run out, esp. when memory is right.
> 2) The default MAX_TABLE_BATCH is static (it is equal to the number of
> pointer we can fit into one page - sizeof(struct mmu_table_batch) ==
> 509), we may want to adjust it for very big systems.
That would then put more stress on the memory allocator because you're
then asking for higher order pages.
next prev parent reply other threads:[~2017-09-29 13:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-27 5:59 kernel test robot
2017-09-29 12:24 ` Vitaly Kuznetsov
2017-09-29 13:13 ` Peter Zijlstra [this message]
2017-09-29 13:16 ` Peter Zijlstra
2017-09-29 14:02 ` Vitaly Kuznetsov
2017-11-20 16:58 ` Vitaly Kuznetsov
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