From: Dave Hansen <dave.hansen@linux.intel.com>
To: Nadav Amit <namit@vmware.com>, x86@kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Nadav Amit <nadav.amit@gmail.com>,
Andy Lutomirski <luto@kernel.org>
Subject: Re: [PATCH] x86: Align TLB invalidation info
Date: Wed, 31 Jan 2018 13:01:24 -0800 [thread overview]
Message-ID: <8bb352bc-4e1f-4e87-80e3-a8e65d618d2a@linux.intel.com> (raw)
In-Reply-To: <20180131201118.1694-1-namit@vmware.com>
On 01/31/2018 12:11 PM, Nadav Amit wrote:
> The TLB invalidation info is allocated on the stack, which might cause
> it to be unaligned. Since this information may be transferred to
> different cores for TLB shootdown, this might result in an additional
> cache-line bouncing between the cores.
>
> GCC provides a way to deal with it by using
> __builtin_alloca_with_align(). Use it to avoid the bouncing cache lines.
It doesn't really *bounce*, though, does it? I don't see any writes on
the remote side. The remote use seems entirely read-only.
You also don't have to exhaustively test this, but I'd love to see at
least a sanity check with a microbenchmark (or something) that, yes,
this does help *something*. Maybe it makes the remote
flush_tlb_func_common() run faster because it's pulling in fewer lines,
or maybe you can even detect fewer misses in there.
next prev parent reply other threads:[~2018-01-31 21:01 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-31 20:11 [PATCH] x86: Align TLB invalidation info Nadav Amit
2018-01-31 20:24 ` Andy Lutomirski
2018-01-31 20:48 ` Nadav Amit
2018-01-31 20:49 ` Dave Hansen
2018-01-31 20:52 ` Nadav Amit
2018-01-31 21:00 ` Andy Lutomirski
2018-01-31 21:01 ` Dave Hansen [this message]
2018-01-31 21:09 ` Nadav Amit
2018-01-31 21:15 ` Andy Lutomirski
2018-01-31 21:17 ` Nadav Amit
[not found] ` <f7270e0d-d1d1-599d-d2c9-ddc2c263e090@linux.intel.com>
2018-02-01 5:38 ` Nadav Amit
2018-02-01 9:38 ` Peter Zijlstra
2018-02-01 18:45 ` Nadav Amit
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