From: Arnd Bergmann <arnd@arndb.de>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Nishanth Menon <nm@ti.com>, Michal Hocko <mhocko@suse.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Rik van Riel <riel@surriel.com>, Roman Gushchin <guro@fb.com>,
Santosh Shilimkar <santosh.shilimkar@oracle.com>,
Dave Chinner <david@fromorbit.com>,
Russell King - ARM Linux admin <linux@armlinux.org.uk>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Tero Kristo <t-kristo@ti.com>, Linux-MM <linux-mm@kvack.org>,
Yafang Shao <laoar.shao@gmail.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Santosh Shilimkar <ssantosh@kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
kernel-team@fb.com, Kishon Vijay Abraham I <kishon@ti.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] vfs: keep inodes with page cache off the inode shrinker LRU
Date: Wed, 11 Mar 2020 23:21:01 +0100 [thread overview]
Message-ID: <CAK8P3a0QTKsqoxE7HS7aNrASSHOfFJHfp3+KZNTVoQ12wHi3VQ@mail.gmail.com> (raw)
In-Reply-To: <20200311172631.GN3216816@arrakis.emea.arm.com>
On Wed, Mar 11, 2020 at 6:26 PM Catalin Marinas <catalin.marinas@arm.com> wrote:
> On Wed, Mar 11, 2020 at 05:59:53PM +0100, Arnd Bergmann wrote:
> > On Wed, Mar 11, 2020 at 3:29 PM Catalin Marinas <catalin.marinas@arm.com> wrote:
> > Do you have an estimate of how long writing to TTBR0_64 takes on Cortex-A7
> > and A15, respectively?
>
> I don't have numbers but it's usually not cheap since you need an ISB to
> synchronise the context after TTBR0 update (basically flushing the
> pipeline).
Ok.
> > Another way might be to use a use a temporary buffer that is already
> > mapped, and add a memcpy() through L1-cache to reduce the number
> > of ttbr0 changes. The buffer would probably have to be on the stack,
> > which limits the size, but for large copies get_user_pages()+memcpy()
> > may end up being faster anyway.
>
> IIRC, the x86 attempt from Ingo some years ago was using
> get_user_pages() for uaccess. Depending on the size of the buffer, this
> may be faster than copying twice.
I guess the tradeoffs for that were rather different, as x86 back
then had no ASIDs, so changing the page tables required a full
TLB flush.
Arnd
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prev parent reply other threads:[~2020-03-11 22:21 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200211175507.178100-1-hannes@cmpxchg.org>
[not found] ` <29b6e848ff4ad69b55201751c9880921266ec7f4.camel@surriel.com>
[not found] ` <20200211193101.GA178975@cmpxchg.org>
[not found] ` <20200211154438.14ef129db412574c5576facf@linux-foundation.org>
[not found] ` <CAHk-=wiGbz3oRvAVFtN-whW-d2F-STKsP1MZT4m_VeycAr1_VQ@mail.gmail.com>
[not found] ` <20200211164701.4ac88d9222e23d1e8cc57c51@linux-foundation.org>
2020-02-12 1:03 ` [PATCH] vfs: keep inodes with page cache off the inode shrinker LRU Linus Torvalds
2020-02-12 8:50 ` Russell King - ARM Linux admin
2020-02-13 9:50 ` Lucas Stach
2020-02-13 16:52 ` Arnd Bergmann
2020-02-15 11:25 ` Geert Uytterhoeven
2020-02-15 16:59 ` Arnd Bergmann
2020-02-16 9:44 ` Geert Uytterhoeven
2020-02-16 19:54 ` Chris Paterson
2020-02-16 20:38 ` Arnd Bergmann
2020-02-20 14:35 ` Chris Paterson
2020-02-26 18:04 ` santosh.shilimkar
2020-02-26 21:01 ` Arnd Bergmann
2020-02-26 21:11 ` santosh.shilimkar
2020-03-06 20:34 ` Nishanth Menon
2020-03-07 1:08 ` santosh.shilimkar
2020-03-08 10:58 ` Arnd Bergmann
2020-03-08 14:19 ` Russell King - ARM Linux admin
2020-03-09 13:33 ` Arnd Bergmann
2020-03-09 14:04 ` Russell King - ARM Linux admin
2020-03-09 15:04 ` Arnd Bergmann
2020-03-10 9:16 ` Michal Hocko
2020-03-09 15:59 ` Catalin Marinas
2020-03-09 16:09 ` Russell King - ARM Linux admin
2020-03-09 16:57 ` Catalin Marinas
2020-03-09 19:46 ` Arnd Bergmann
2020-03-11 14:29 ` Catalin Marinas
2020-03-11 16:59 ` Arnd Bergmann
2020-03-11 17:26 ` Catalin Marinas
2020-03-11 22:21 ` Arnd Bergmann [this message]
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