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Re: [PATCH] xen: make multicall debug boot time selectable
- To: Jürgen Groß <jgross@xxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx, linux-doc@xxxxxxxxxxxxxxx
- From: boris.ostrovsky@xxxxxxxxxx
- Date: Mon, 8 Jul 2024 10:32:46 -0400
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- Cc: Jonathan Corbet <corbet@xxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Mon, 08 Jul 2024 14:33:30 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 7/8/24 5:04 AM, Jürgen Groß wrote:
On 06.07.24 00:36, boris.ostrovsky@xxxxxxxxxx wrote:
Also, would it be better to keep these fields as a struct of scalars
and instead have the percpu array of this struct? Otherwise there is a
whole bunch of [MC_BATCH] arrays, all of them really indexed by the
same value. (And while at it, there is no reason to have
callbacks[MC_BATCH] sized like that -- it has nothing to do with batch
size and can probably be made smaller)
As today the mc_buffer's entries are copied via a single memcpy(), there
are 3 options:
Ah yes, it's memcpy, I didn't think of that. Then leaving it as is is
the best.
- make mc_debug_data a percpu pointer to a single array, requiring to
copy the mc_buffer's entries in a loop
- let struct mc_debug_data contain two arrays (entries[] and struct foo
{}[],
with struct foo containing the other pointers/values)
- keep the layout as in my patch
Regarding the callbacks: I think the max number of callbacks is indeed
MC_BATCH,
as for each batch member one callback might be requested. So I'd rather
keep it
the way it is today.
Right, I was trying to point out that it's the max number but I suspect
it usually is smaller -- we currently ask for a callback in fewer than
half of the cases where we submit a request.
-boris
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