From: Alexander Lobakin <aleksander.lobakin@intel.com>
To: Christoph Hellwig <hch@lst.de>
Cc: "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
"Robin Murphy" <robin.murphy@arm.com>,
Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Magnus Karlsson <magnus.karlsson@intel.com>,
Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
Alexander Duyck <alexanderduyck@fb.com>, <bpf@vger.kernel.org>,
<netdev@vger.kernel.org>, <iommu@lists.linux.dev>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net-next 1/7] dma: compile-out DMA sync op calls when not used
Date: Mon, 29 Jan 2024 12:07:30 +0100 [thread overview]
Message-ID: <4e23d103-ea1c-4fd3-852e-f7e2ec9170ad@intel.com> (raw)
In-Reply-To: <20240129061136.GD19258@lst.de>
From: Christoph Hellwig <hch@lst.de>
Date: Mon, 29 Jan 2024 07:11:36 +0100
> On Fri, Jan 26, 2024 at 02:54:50PM +0100, Alexander Lobakin wrote:
>> Some platforms do have DMA, but DMA there is always direct and coherent.
>> Currently, even on such platforms DMA sync operations are compiled and
>> called.
>> Add a new hidden Kconfig symbol, DMA_NEED_SYNC, and set it only when
>> either sync operations are needed or there is DMA ops or swiotlb
>> enabled. Set dma_need_sync() and dma_skip_sync() (stub for now)
>> depending on this symbol state and don't call sync ops when
>> dma_skip_sync() is true.
>> The change allows for future optimizations of DMA sync calls depending
>> on compile-time or runtime conditions.
>
> So the idea of compiling out the calls sounds fine to me. But what
> is the point of the extra indirection through the __-prefixed calls?
Because dma_sync_* ops are external functions, not inlines, and in the
next patch I'm adding a check there.
>
> And if we need that (please document it in the commit log), please
> make the wrappers proper inline functions and not macros.
Thanks,
Olek
next prev parent reply other threads:[~2024-01-29 11:08 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-26 13:54 [PATCH net-next 0/7] dma: skip calling no-op sync ops when possible Alexander Lobakin
2024-01-26 13:54 ` [PATCH net-next 1/7] dma: compile-out DMA sync op calls when not used Alexander Lobakin
2024-01-29 6:11 ` Christoph Hellwig
2024-01-29 11:07 ` Alexander Lobakin [this message]
2024-01-29 12:15 ` Robin Murphy
2024-01-31 16:52 ` Simon Horman
2024-01-31 17:14 ` Robin Murphy
2024-01-26 13:54 ` [PATCH net-next 2/7] dma: avoid expensive redundant calls for sync operations Alexander Lobakin
2024-01-26 15:48 ` Robin Murphy
2024-01-26 16:45 ` Alexander Lobakin
2024-01-26 17:21 ` Robin Murphy
2024-01-26 18:48 ` Petr Tesařík
2024-01-26 19:13 ` Robin Murphy
2024-01-29 6:09 ` Christoph Hellwig
2024-01-29 14:36 ` Alexander Lobakin
2024-01-29 16:15 ` Petr Tesařík
2024-01-29 14:07 ` Alexander Lobakin
2024-01-29 14:29 ` Robin Murphy
2024-01-29 14:34 ` Alexander Lobakin
2024-01-26 13:54 ` [PATCH net-next 3/7] iommu/dma: avoid expensive indirect " Alexander Lobakin
2024-01-26 13:54 ` [PATCH net-next 4/7] page_pool: make sure frag API fields don't span between cachelines Alexander Lobakin
2024-01-26 13:54 ` [PATCH net-next 5/7] page_pool: don't use driver-set flags field directly Alexander Lobakin
2024-01-26 13:54 ` [PATCH net-next 6/7] page_pool: check for DMA sync shortcut earlier Alexander Lobakin
2024-01-26 13:54 ` [PATCH net-next 7/7] xsk: use generic DMA sync shortcut instead of a custom one Alexander Lobakin
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