linux-kernel - Re: [regression v4.0-rc1] mm: IPIs from TLB flushes causing significant performance degradation.

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]

Date:	Mon, 2 Mar 2015 18:22:29 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Dave Chinner <david@...morbit.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>, Matt B <jackdachef@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>, xfs@....sgi.com
Subject: Re: [regression v4.0-rc1] mm: IPIs from TLB flushes causing
 significant performance degradation.

On Mon, Mar 2, 2015 at 5:47 PM, Dave Chinner <david@...morbit.com> wrote:
>
> Anyway, the difference between good and bad is pretty clear, so
> I'm pretty confident the bisect is solid:
>
> 4d9424669946532be754a6e116618dcb58430cb4 is the first bad commit

Well, it's the mm queue from Andrew, so I'm not surprised. That said,
I don't see why that particular one should matter.

Hmm. In your profiles, can you tell which caller of "flush_tlb_page()"
 changed the most? The change from "mknnuma" to "prot_none" *should*
be 100% equivalent (both just change the page to be not-present, just
set different bits elsewhere in the pte), but clearly something
wasn't.

Oh. Except for that special "huge-zero-page" special case that got
dropped, but that got re-introduced in commit e944fd67b625.

There might be some other case where the new "just change the
protection" doesn't do the "oh, but it the protection didn't change,
don't bother flushing". I don't see it.

                          Linus
--
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/