linux-kernel - Re: [PATCH 3/5] x86: mm: Eliminate redundant page table walk during TLB range flushing

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <52CEFD4F.3080804@redhat.com>
Date:	Thu, 09 Jan 2014 14:49:35 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Mel Gorman <mgorman@...e.de>, Alex Shi <alex.shi@...aro.org>,
	Ingo Molnar <mingo@...nel.org>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Fengguang Wu <fengguang.wu@...el.com>,
	H Peter Anvin <hpa@...or.com>, Linux-X86 <x86@...nel.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/5] x86: mm: Eliminate redundant page table walk during
 TLB range flushing

On 01/09/2014 09:34 AM, Mel Gorman wrote:
> When choosing between doing an address space or ranged flush, the x86
> implementation of flush_tlb_mm_range takes into account whether there are
> any large pages in the range. A per-page flush typically requires fewer
> entries than would covered by a single large page and the check is redundant.
>
> There is one potential exception. THP migration flushes single THP entries
> and it conceivably would benefit from flushing a single entry instead
> of the mm. However, this flush is after a THP allocation, copy and page
> table update potentially with any other threads serialised behind it. In
> comparison to that, the flush is noise. It makes more sense to optimise
> balancing to require fewer flushes than to optimise the flush itself.
>
> This patch deletes the redundant huge page check.
>
> Signed-off-by: Mel Gorman <mgorman@...e.de>

Reviewed-by: Rik van Riel <riel@...hat.com>

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/