From: Peter Zijlstra <peterz@infradead.org>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Gerald Schaefer <gerald.schaefer@de.ibm.com>,
Steve Capper <steve.capper@linaro.org>,
Dann Frazier <dann.frazier@canonical.com>,
Catalin Marinas <catalin.marinas@arm.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, Martin Schwidefsky <schwidefsky@de.ibm.com>
Subject: Re: [PATCH] thp, mm: remove comments on serializion of THP split vs. gup_fast
Date: Fri, 11 Mar 2016 10:22:18 +0100 [thread overview]
Message-ID: <20160311092218.GY6344@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160310172249.GG30716@redhat.com>
On Thu, Mar 10, 2016 at 06:22:49PM +0100, Andrea Arcangeli wrote:
> On Thu, Mar 10, 2016 at 06:04:06PM +0100, Andrea Arcangeli wrote:
> > that costs memory in the mm unless we're lucky with the slab hw
> > alignment), then I think synchronize_srcu may actually be preferable
> > than a full synchronize_sched that affects the entire system with
> > thousand of CPUs. A per-cpu inc wouldn't be a big deal and it would at
> > least avoid to stall for the whole system if a stall eventually has to
> > happen (unless every cpu is actually running gup_fast but that's ok in
> > such case).
>
> Thinking more about this, it'd be ok if the pgtable freeing srcu
> context was global, no need of mess with the mm. A __percpu inside mm
> wouldn't fly anyway. With srcu we'd wait only for those CPUs that are
> effectively inside gup_fast, most of the time none or a few.
You've not looked at srcu, right? That's not going to make it faster,
not without some serious surgery.
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prev parent reply other threads:[~2016-03-11 9:22 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-24 15:59 [PATCH] thp, mm: remove comments on serializion of THP split vs. gup_fast Kirill A. Shutemov
2016-02-24 17:50 ` Gerald Schaefer
2016-02-25 15:07 ` Kirill A. Shutemov
2016-02-26 6:50 ` Hugh Dickins
2016-02-26 11:06 ` Peter Zijlstra
2016-02-26 11:41 ` Martin Schwidefsky
2016-02-29 2:38 ` Hugh Dickins
2016-03-10 16:10 ` Andrea Arcangeli
2016-03-10 16:34 ` Peter Zijlstra
2016-03-10 16:40 ` Peter Zijlstra
2016-03-10 17:04 ` Andrea Arcangeli
2016-03-10 17:22 ` Andrea Arcangeli
2016-03-11 9:22 ` Peter Zijlstra [this message]
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