From: Dave Hansen <dave.hansen@intel.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
David Rientjes <rientjes@google.com>
Cc: linux-mm <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [PATCH] mm: Flush the TLB for a single address in a huge page
Date: Wed, 22 Jul 2015 16:05:21 -0700 [thread overview]
Message-ID: <55B021B1.5020409@intel.com> (raw)
In-Reply-To: <CAHkRjk7=VMG63VfZdWbZqYu8FOa9M+54Mmdro661E2zt3WToog@mail.gmail.com>
On 07/22/2015 03:48 PM, Catalin Marinas wrote:
> You are right, on x86 the tlb_single_page_flush_ceiling seems to be
> 33, so for an HPAGE_SIZE range the code does a local_flush_tlb()
> always. I would say a single page TLB flush is more efficient than a
> whole TLB flush but I'm not familiar enough with x86.
The last time I looked, the instruction to invalidate a single page is
more expensive than the instruction to flush the entire TLB. We also
don't bother doing ranged flushes _ever_ for hugetlbfs TLB
invalidations, but that was just because the work done around commit
e7b52ffd4 didn't see any benefit.
That said, I can't imagine this will hurt anything. We also have TLBs
that can mix 2M and 4k pages and I don't think we did back when we put
that code in originally.
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next prev parent reply other threads:[~2015-07-22 23:05 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-22 17:13 Catalin Marinas
2015-07-22 21:39 ` David Rientjes
2015-07-22 22:48 ` Catalin Marinas
2015-07-22 23:05 ` Dave Hansen [this message]
2015-07-23 10:49 ` Catalin Marinas
2015-07-23 14:13 ` Andrea Arcangeli
2015-07-23 14:41 ` Dave Hansen
2015-07-23 15:58 ` Andrea Arcangeli
2015-07-23 16:52 ` Dave Hansen
2015-07-23 16:16 ` Catalin Marinas
2015-07-23 16:55 ` Dave Hansen
2015-07-23 17:13 ` Andrea Arcangeli
2015-07-23 16:49 ` Catalin Marinas
2015-07-24 7:17 ` Martin Schwidefsky
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