From: Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
To: Dmitry Osipenko <digetx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Jonathan Hunter
<jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
Thierry Reding
<thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH v1 4/4] iommu/tegra: gart: Optimize map/unmap
Date: Mon, 7 May 2018 10:04:20 +0200 [thread overview]
Message-ID: <20180507080420.GB18595@8bytes.org> (raw)
In-Reply-To: <6827bda3-1aa2-da60-a749-8e2dd2e595f3-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
On Mon, May 07, 2018 at 12:19:01AM +0300, Dmitry Osipenko wrote:
> Probably the best variant would be to give an explicit control over syncing to a
> user of the IOMMU API, like for example device driver may perform multiple
> mappings / unmappings and then sync/flush in the end. I'm not sure that it's
> really worth the hassle to shuffle the API right now, maybe we can implement it
> later if needed. Joerg, do you have objections to a 'compound page' approach?
Have you measured the performance difference on both variants? The
compound-page approach only works for cases when the physical memory you
map contiguous and correctly aligned.
If it is really needed I would prefer a separate iotlb_sync_map()
call-back that is just NULL when not needed. This way all users that
don't need it only get a minimal penalty in the mapping path and you
don't have any requirements on the physical memory you map to get good
performance.
Joerg
WARNING: multiple messages have this Message-ID (diff)
From: Joerg Roedel <joro@8bytes.org>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Robin Murphy <robin.murphy@arm.com>,
Thierry Reding <thierry.reding@gmail.com>,
linux-tegra@vger.kernel.org, iommu@lists.linux-foundation.org,
linux-kernel@vger.kernel.org,
Jonathan Hunter <jonathanh@nvidia.com>
Subject: Re: [PATCH v1 4/4] iommu/tegra: gart: Optimize map/unmap
Date: Mon, 7 May 2018 10:04:20 +0200 [thread overview]
Message-ID: <20180507080420.GB18595@8bytes.org> (raw)
In-Reply-To: <6827bda3-1aa2-da60-a749-8e2dd2e595f3@gmail.com>
On Mon, May 07, 2018 at 12:19:01AM +0300, Dmitry Osipenko wrote:
> Probably the best variant would be to give an explicit control over syncing to a
> user of the IOMMU API, like for example device driver may perform multiple
> mappings / unmappings and then sync/flush in the end. I'm not sure that it's
> really worth the hassle to shuffle the API right now, maybe we can implement it
> later if needed. Joerg, do you have objections to a 'compound page' approach?
Have you measured the performance difference on both variants? The
compound-page approach only works for cases when the physical memory you
map contiguous and correctly aligned.
If it is really needed I would prefer a separate iotlb_sync_map()
call-back that is just NULL when not needed. This way all users that
don't need it only get a minimal penalty in the mapping path and you
don't have any requirements on the physical memory you map to get good
performance.
Joerg
next prev parent reply other threads:[~2018-05-07 8:04 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-09 20:07 [PATCH v1 0/4] Tegra GART fixes and improvements Dmitry Osipenko
2018-04-09 20:07 ` Dmitry Osipenko
[not found] ` <cover.1523304324.git.digetx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-04-09 20:07 ` [PATCH v1 1/4] iommu/tegra: gart: Add debugging facility Dmitry Osipenko
2018-04-09 20:07 ` Dmitry Osipenko
2018-04-27 9:46 ` Thierry Reding
2018-04-09 20:07 ` [PATCH v1 2/4] iommu/tegra: gart: Fix gart_iommu_unmap() Dmitry Osipenko
2018-04-09 20:07 ` Dmitry Osipenko
[not found] ` <dd25a9ff7bad7c92b345c0c0ce2bf235c4c3b6e8.1523304324.git.digetx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-04-27 9:43 ` Thierry Reding
2018-04-27 9:43 ` Thierry Reding
2018-04-09 20:07 ` [PATCH v1 3/4] iommu/tegra: gart: Constify number of GART pages Dmitry Osipenko
2018-04-09 20:07 ` Dmitry Osipenko
[not found] ` <954659be6760130f6ffd5e733db2ad58cbb8e6e4.1523304324.git.digetx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-04-27 9:49 ` Thierry Reding
2018-04-27 9:49 ` Thierry Reding
2018-04-09 20:07 ` [PATCH v1 4/4] iommu/tegra: gart: Optimize map/unmap Dmitry Osipenko
2018-04-09 20:07 ` Dmitry Osipenko
[not found] ` <f21a7b6a8f141b87f75687904a76f3728ea639a8.1523304324.git.digetx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-04-27 10:02 ` Thierry Reding
2018-04-27 10:02 ` Thierry Reding
2018-04-27 12:01 ` Dmitry Osipenko
2018-04-27 12:36 ` Robin Murphy
2018-04-27 12:36 ` Robin Murphy
[not found] ` <716edf58-38a7-21e5-1668-b866bf392e34-5wv7dgnIgG8@public.gmane.org>
2018-05-06 21:19 ` Dmitry Osipenko
2018-05-06 21:19 ` Dmitry Osipenko
[not found] ` <6827bda3-1aa2-da60-a749-8e2dd2e595f3-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-05-07 8:04 ` Joerg Roedel [this message]
2018-05-07 8:04 ` Joerg Roedel
[not found] ` <20180507080420.GB18595-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
2018-05-07 15:51 ` Dmitry Osipenko
2018-05-07 15:51 ` Dmitry Osipenko
[not found] ` <a6e26d17-97ac-d02e-7bf4-f009af1a25dc-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-05-07 17:38 ` Dmitry Osipenko
2018-05-07 17:38 ` Dmitry Osipenko
2018-05-07 7:59 ` Joerg Roedel
2018-05-07 7:59 ` Joerg Roedel
[not found] ` <20180507075920.GA18595-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
2018-05-07 15:46 ` Dmitry Osipenko
2018-05-07 15:46 ` Dmitry Osipenko
2018-05-03 12:52 ` [PATCH v1 0/4] Tegra GART fixes and improvements Joerg Roedel
2018-05-03 12:52 ` Joerg Roedel
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