From: Andrew Morton <akpm@linux-foundation.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Waiman Long <longman@redhat.com>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Dave Chinner <david@fromorbit.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] list_lru: Prefetch neighboring list entries before acquiring lock
Date: Tue, 5 Dec 2017 15:56:18 -0800 [thread overview]
Message-ID: <20171205155618.7a3a59751ed49c704210b736@linux-foundation.org> (raw)
In-Reply-To: <20171205144948.ezgo3xpjeytkq6ua@dhcp22.suse.cz>
On Tue, 5 Dec 2017 15:49:48 +0100 Michal Hocko <mhocko@kernel.org> wrote:
> On Wed 29-11-17 09:17:34, Waiman Long wrote:
> > The list_lru_del() function removes the given item from the LRU list.
> > The operation looks simple, but it involves writing into the cachelines
> > of the two neighboring list entries in order to get the deletion done.
> > That can take a while if the cachelines aren't there yet, thus
> > prolonging the lock hold time.
> >
> > To reduce the lock hold time, the cachelines of the two neighboring
> > list entries are now prefetched before acquiring the list_lru_node's
> > lock.
> >
> > Using a multi-threaded test program that created a large number
> > of dentries and then killed them, the execution time was reduced
> > from 38.5s to 36.6s after applying the patch on a 2-socket 36-core
> > 72-thread x86-64 system.
> >
> > Signed-off-by: Waiman Long <longman@redhat.com>
>
> The patch still seems to be in the mmotm tree while it breaks
> compilation. At least m32r defconfig complains with
> mm/list_lru.c: In function 'list_lru_del':
> mm/list_lru.c:141:2: error: implicit declaration of function 'prefetchw' [-Werror=implicit-function-declaration]
> prefetchw(item->prev);
erp, I forgot to cc Stephen.
> It also seems that there is no general agreement in the patch. Andrew,
> do you plan to keep it?
It's in wait-and-see mode.
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next prev parent reply other threads:[~2017-12-05 23:56 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-29 14:17 [PATCH] list_lru: Prefetch neighboring list entries before acquiring lock Waiman Long
2017-11-29 21:53 ` Andrew Morton
2017-11-30 0:42 ` Dave Chinner
2017-11-30 13:54 ` Waiman Long
2017-11-30 20:38 ` Dave Chinner
2017-11-30 20:55 ` Waiman Long
2017-11-30 20:47 ` Andrew Morton
2017-11-30 20:49 ` Waiman Long
2017-12-01 0:09 ` Minchan Kim
2017-12-01 14:14 ` Waiman Long
2017-12-01 22:02 ` Dave Chinner
2017-11-30 0:53 ` Minchan Kim
2017-11-30 13:43 ` Waiman Long
2017-11-30 23:53 ` Minchan Kim
2017-11-30 14:34 ` Matthew Wilcox
2017-12-05 14:49 ` Michal Hocko
2017-12-05 23:56 ` Andrew Morton [this message]
2017-12-06 8:07 ` Michal Hocko
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