From: "H. Peter Anvin" <hpa@zytor.com>
To: Alex Shi <alex.shi@intel.com>
Cc: mgorman@suse.de, npiggin@gmail.com, tglx@linutronix.de,
mingo@redhat.com, arnd@arndb.de, rostedt@goodmis.org,
fweisbec@gmail.com, jeremy@goop.org, gregkh@linuxfoundation.org,
glommer@redhat.com, riel@redhat.com, luto@mit.edu,
avi@redhat.com, len.brown@intel.com, dhowells@redhat.com,
fenghua.yu@intel.com, borislav.petkov@amd.com,
yinghai@kernel.org, ak@linux.intel.com, cpw@sgi.com,
steiner@sgi.com, akpm@linux-foundation.org, penberg@kernel.org,
hughd@google.com, rientjes@google.com,
kosaki.motohiro@jp.fujitsu.com, n-horiguchi@ah.jp.nec.com,
paul.gortmaker@windriver.com, trenn@suse.de, tj@kernel.org,
oleg@redhat.com, axboe@kernel.dk, a.p.zijlstra@chello.nl,
kamezawa.hiroyu@jp.fujitsu.com, viro@zeniv.linux.org.uk,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 4/7] x86/tlb: add tlb flush all factor for specific CPUs
Date: Tue, 08 May 2012 08:15:58 -0700 [thread overview]
Message-ID: <4FA938AE.9070209@zytor.com> (raw)
In-Reply-To: <1336485790-30902-5-git-send-email-alex.shi@intel.com>
On 05/08/2012 07:03 AM, Alex Shi wrote:
>
> like some machine in my hands, balance points is 16 entries on Romely-EP;
> while it is at 8 entries on Bloomfield NHM-EP; but on model 15 core2 Xeon
> using invlpg has nothing help.
>
> For untested machine, no optimization now.
>
This seems a bit concerning from a forward compatibility point of view.
It would make more sense to assume that future processors would behave
more like the most recent (Sandy Bridge in your case) unless there is
evidence to the contrary.
>
> - if ((end - start)/PAGE_SIZE > act_entries/FLUSHALL_BAR)
> + if ((end - start)/PAGE_SIZE >
> + act_entries/tlb_flushall_factor)
> local_flush_tlb();
You are doing a dynamic division (and on unknown/older CPUs you're
dividing by zero!!) but all your divisors are powers of two. Make it a
shift instead.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2012-05-08 15:16 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-08 14:03 [PATCH v3] TLB flush optimization Alex Shi
2012-05-08 14:03 ` [PATCH v3 1/7] x86/tlb_info: get last level TLB entry number of CPU Alex Shi
2012-05-08 14:03 ` [PATCH v3 2/7] x86/flush_tlb: try flush_tlb_single one by one in flush_tlb_range Alex Shi
2012-05-08 14:03 ` [PATCH v3 3/7] x86/tlb: fall back to flush all when meet a THP large page Alex Shi
2012-05-08 14:03 ` [PATCH v3 4/7] x86/tlb: add tlb flush all factor for specific CPUs Alex Shi
2012-05-08 15:08 ` Peter Zijlstra
2012-05-09 2:03 ` Alex Shi
2012-05-08 15:12 ` H. Peter Anvin
2012-05-09 2:10 ` Alex Shi
2012-05-08 15:15 ` H. Peter Anvin [this message]
2012-05-08 15:56 ` Andi Kleen
2012-05-08 16:40 ` H. Peter Anvin
2012-05-08 15:18 ` H. Peter Anvin
2012-05-09 1:41 ` Alex Shi
2012-05-08 14:03 ` [PATCH v3 5/7] x86/tlb: remove comments for tlb_flush_range implement suggestion Alex Shi
2012-05-09 8:22 ` Nick Piggin
2012-05-08 14:03 ` [PATCH v3 6/7] x86/tlb: optimizing flush_tlb_mm Alex Shi
2012-05-08 15:09 ` Peter Zijlstra
2012-05-08 14:03 ` [PATCH v3 7/7] x86/tlb: add tlb_flushall_factor into sysfs for user change Alex Shi
2012-05-08 15:11 ` Peter Zijlstra
2012-05-08 15:20 ` H. Peter Anvin
2012-05-08 15:25 ` Borislav Petkov
2012-05-08 15:31 ` H. Peter Anvin
2012-05-08 15:41 ` Borislav Petkov
2012-05-08 15:48 ` H. Peter Anvin
2012-05-08 16:10 ` Greg KH
2012-05-08 16:28 ` Borislav Petkov
2012-05-09 5:03 ` Alex Shi
2012-05-08 15:01 ` [PATCH v3] TLB flush optimization Peter Zijlstra
2012-05-09 1:58 ` Alex Shi
2012-05-09 23:45 ` Andi Kleen
2012-05-10 5:06 ` Alex Shi
2012-05-10 7:49 ` HATAYAMA Daisuke
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