From: Borislav Petkov <bp@alien8.de>
To: "Kalra, Ashish" <Ashish.Kalra@amd.com>
Cc: "Lendacky, Thomas" <Thomas.Lendacky@amd.com>,
"Grimm, Jon" <Jon.Grimm@amd.com>,
"Singh, Brijesh" <brijesh.singh@amd.com>,
"dave.hansen@linux-intel.com" <dave.hansen@linux-intel.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
"mingo@redhat.com" <mingo@redhat.com>,
"luto@kernel.org" <luto@kernel.org>,
"hpa@zytor.com" <hpa@zytor.com>,
"rientjes@google.com" <rientjes@google.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"hch@lst.de" <hch@lst.de>
Subject: Re: [PATCH v6] swiotlb: Adjust SWIOTBL bounce buffer size for SEV guests.
Date: Tue, 24 Nov 2020 10:38:37 +0100 [thread overview]
Message-ID: <20201124093837.GD4009@zn.tnic> (raw)
In-Reply-To: <EF13C80C-42DC-4B51-8AF8-2C1D3859B490@amd.com>
On Tue, Nov 24, 2020 at 09:25:06AM +0000, Kalra, Ashish wrote:
> But what will be the criteria to figure out this percentage?
>
> As I mentioned earlier, this can be made as complicated as possible by
> adding all kind of heuristics but without any predictable performance
> gain.
>
> Or it can be kept simple by using a static percentage value.
Yes, static percentage number based on the guest memory. X% of the guest
memory is used for SWIOTLB.
Since you use sev_active(), it means the size computation is done in the
guest so that SWIOTLB size is per-guest. Yes?
If so, you can simply take, say, 5% of the guest memory's size and use
that for SWIOTLB buffers. Or 6 or X or whatever.
Makes sense?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
WARNING: multiple messages have this Message-ID (diff)
From: Borislav Petkov <bp@alien8.de>
To: "Kalra, Ashish" <Ashish.Kalra@amd.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
"hch@lst.de" <hch@lst.de>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"hpa@zytor.com" <hpa@zytor.com>,
"x86@kernel.org" <x86@kernel.org>,
"luto@kernel.org" <luto@kernel.org>,
"peterz@infradead.org" <peterz@infradead.org>,
"dave.hansen@linux-intel.com" <dave.hansen@linux-intel.com>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Singh, Brijesh" <brijesh.singh@amd.com>,
"Lendacky, Thomas" <Thomas.Lendacky@amd.com>,
"Grimm, Jon" <Jon.Grimm@amd.com>,
"rientjes@google.com" <rientjes@google.com>
Subject: Re: [PATCH v6] swiotlb: Adjust SWIOTBL bounce buffer size for SEV guests.
Date: Tue, 24 Nov 2020 10:38:37 +0100 [thread overview]
Message-ID: <20201124093837.GD4009@zn.tnic> (raw)
In-Reply-To: <EF13C80C-42DC-4B51-8AF8-2C1D3859B490@amd.com>
On Tue, Nov 24, 2020 at 09:25:06AM +0000, Kalra, Ashish wrote:
> But what will be the criteria to figure out this percentage?
>
> As I mentioned earlier, this can be made as complicated as possible by
> adding all kind of heuristics but without any predictable performance
> gain.
>
> Or it can be kept simple by using a static percentage value.
Yes, static percentage number based on the guest memory. X% of the guest
memory is used for SWIOTLB.
Since you use sev_active(), it means the size computation is done in the
guest so that SWIOTLB size is per-guest. Yes?
If so, you can simply take, say, 5% of the guest memory's size and use
that for SWIOTLB buffers. Or 6 or X or whatever.
Makes sense?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2020-11-24 9:38 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-19 21:42 [PATCH v6] swiotlb: Adjust SWIOTBL bounce buffer size for SEV guests Ashish Kalra
2020-11-19 21:42 ` Ashish Kalra
2020-11-23 17:06 ` Borislav Petkov
2020-11-23 17:06 ` Borislav Petkov
2020-11-23 17:56 ` Konrad Rzeszutek Wilk
2020-11-23 17:56 ` Konrad Rzeszutek Wilk
2020-11-23 18:02 ` Borislav Petkov
2020-11-23 18:02 ` Borislav Petkov
2020-11-23 18:43 ` Konrad Rzeszutek Wilk
2020-11-23 18:43 ` Konrad Rzeszutek Wilk
2020-11-24 9:00 ` Borislav Petkov
2020-11-24 9:00 ` Borislav Petkov
2020-11-23 22:56 ` Ashish Kalra
2020-11-23 22:56 ` Ashish Kalra
2020-11-24 9:04 ` Borislav Petkov
2020-11-24 9:04 ` Borislav Petkov
2020-11-24 9:25 ` Kalra, Ashish
2020-11-24 9:25 ` Kalra, Ashish
2020-11-24 9:38 ` Borislav Petkov [this message]
2020-11-24 9:38 ` Borislav Petkov
2020-11-24 9:43 ` Kalra, Ashish
2020-11-24 9:43 ` Kalra, Ashish
2020-11-24 23:46 ` Ashish Kalra
2020-11-24 23:46 ` Ashish Kalra
2020-12-01 20:42 ` Konrad Rzeszutek Wilk
2020-12-01 20:42 ` Konrad Rzeszutek Wilk
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20201124093837.GD4009@zn.tnic \
--to=bp@alien8.de \
--cc=Ashish.Kalra@amd.com \
--cc=Jon.Grimm@amd.com \
--cc=Thomas.Lendacky@amd.com \
--cc=brijesh.singh@amd.com \
--cc=dave.hansen@linux-intel.com \
--cc=hch@lst.de \
--cc=hpa@zytor.com \
--cc=iommu@lists.linux-foundation.org \
--cc=konrad.wilk@oracle.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=rientjes@google.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.