From: Linus Walleij <linus.walleij@linaro.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Ulf Hansson <ulf.hansson@linaro.org>,
Christoph Hellwig <hch@lst.de>,
Russell King <linux@armlinux.org.uk>,
Nicolas Pitre <nico@fluxnic.net>,
Aaro Koskinen <aaro.koskinen@iki.fi>,
Ben Dooks <ben-linux@fluff.org>,
"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
linux-omap <linux-omap@vger.kernel.org>,
"list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
Joerg Roedel <joro@8bytes.org>,"
<iommu@lists.linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: remove block layer bounce buffering for MMC
Date: Wed, 16 Jan 2019 14:51:16 +0100 [thread overview]
Message-ID: <CACRpkdY4SRxJiH8PEwTNAyPum_=e3VhG30y8wJhfcdML--9BdQ@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a16ZoBt=HpZByb_1iH+-0e9O0F0sPX+ROfO9hWnJR94qg@mail.gmail.com>
On Wed, Jan 16, 2019 at 11:25 AM Arnd Bergmann <arnd@arndb.de> wrote:
> On Mon, Jan 14, 2019 at 11:27 AM Ulf Hansson <ulf.hansson@linaro.org> wrote:
> >
> > +Linus Walleij (recently made a cleanup of the mmc bounce buffering code).
Nah it's not THAT bounce buffer.
> Linus probably knows more here, but I have a vague recollection of
> the MMC bounce buffer code being needed mostly for performance
> reasons: when the scatterlist is discontiguous, that can result in
> a request being split up into separate MMC commands, which due
> to the lack of queued commands combined with the need for
> garbage collection on sub-page writes results in a huge slowdown
> compared to having larger bounce buffers all the time.
>
> We had discussed finding a different way to do this (separate
> from the bounce buffering), but I don't know if that ever happened,
> or if this is even the code that you are changing here.
Nope not the same code.
The term "bounce buffer" is sadly used as ambigously as
__underscores in front of function names.
That other "bounce buffer" was first deleted and then
reimplemented as a local hack in the SDHCI driver core
after it caused performance regressions on the i.MX and
some laptops, see commit:
commit bd9b902798ab14d19ca116b10bde581ddff8f905
mmc: sdhci: Implement an SDHCI-specific bounce buffer
That should be orthogonal to Christoph's changes in this
patch series.
Yours,
Linus Walleij
next prev parent reply other threads:[~2019-01-16 13:51 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-14 9:57 remove block layer bounce buffering for MMC Christoph Hellwig
2019-01-14 9:57 ` [PATCH 01/11] mmc: davinci: handle highmem pages Christoph Hellwig
2019-01-14 9:57 ` [PATCH 02/11] mmc: moxart: " Christoph Hellwig
2019-01-14 9:57 ` [PATCH 03/11] mmc: omap: " Christoph Hellwig
2019-01-14 9:57 ` [PATCH 04/11] mmc: omap: handle chained sglists Christoph Hellwig
2019-01-14 9:57 ` [PATCH 05/11] mmc: s3cmci: handle highmem pages Christoph Hellwig
2019-01-30 7:57 ` Ulf Hansson
2019-01-30 8:04 ` Christoph Hellwig
2019-01-30 8:16 ` Ulf Hansson
2019-01-14 9:57 ` [PATCH 06/11] mmc: s3cmci: handle chained sglists Christoph Hellwig
2019-01-14 9:58 ` [PATCH 07/11] mmc: mvsdio: handle highmem pages Christoph Hellwig
2019-01-14 16:29 ` Nicolas Pitre
2019-01-30 7:55 ` Ulf Hansson
2019-01-14 9:58 ` [PATCH 08/11] mmc: sh_mmcif: " Christoph Hellwig
2019-01-14 9:58 ` [PATCH 09/11] mmc: sh_mmcif: handle chained sglists Christoph Hellwig
2019-01-14 9:58 ` [PATCH 10/11] mmc: core: don't use block layer bounce buffers Christoph Hellwig
2019-01-14 9:58 ` [PATCH 11/11] dma-mapping: remove dma_max_pfn Christoph Hellwig
2019-01-14 10:26 ` remove block layer bounce buffering for MMC Ulf Hansson
2019-01-16 10:24 ` Arnd Bergmann
2019-01-16 13:51 ` Linus Walleij [this message]
2019-01-16 13:54 ` Arnd Bergmann
2019-01-14 16:52 ` Robin Murphy
2019-01-14 16:57 ` Christoph Hellwig
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