linux-kernel - Re: [PATCH v3] sparc64: Reduce TLB flushes during hugepte changes

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Date:	Tue, 29 Mar 2016 19:41:05 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	nitin.m.gupta@...cle.com
Cc:	akpm@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
	khalid.aziz@...cle.com, minchan@...nel.org,
	aneesh.kumar@...ux.vnet.ibm.com, zhenzhang.zhang@...wei.com,
	sfr@...b.auug.org.au, mingo@...nel.org, chris.hyser@...cle.com,
	dahi@...ux.vnet.ibm.com, toshi.kani@....com, tony.luck@...el.com,
	sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] sparc64: Reduce TLB flushes during hugepte changes

From: Nitin Gupta <nitin.m.gupta@...cle.com>
Date: Tue, 29 Mar 2016 14:11:14 -0700

> During hugepage map/unmap, TSB and TLB flushes are currently
> issued at every PAGE_SIZE'd boundary which is unnecessary.
> We now issue the flush at REAL_HPAGE_SIZE boundaries only.
> 
> Without this patch workloads which unmap a large hugepage
> backed VMA region get CPU lockups due to excessive TLB
> flush calls.
> 
> Orabug: 22365539, 22643230, 22995196
> 
> Signed-off-by: Nitin Gupta <nitin.m.gupta@...cle.com>

You really need to put some more work into this, there are lots of
config variants you didn't even test.

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