On 03/23/2017 07:35 PM, David Miller wrote:
From: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Date: Thu, 23 Mar 2017 16:26:38 -0700
On Thu, Mar 23, 2017 at 07:01:48PM -0400, Pavel Tatashin wrote:
When deferred struct page initialization feature is enabled, we get a
performance gain of initializing vmemmap in parallel after other CPUs are
started. However, we still zero the memory for vmemmap using one boot CPU.
This patch-set fixes the memset-zeroing limitation by deferring it as well.
Here is example performance gain on SPARC with 32T:
base
https://hastebin.com/ozanelatat.go
fix
https://hastebin.com/utonawukof.go
As you can see without the fix it takes: 97.89s to boot
With the fix it takes: 46.91 to boot.
How long does it take if we just don't zero this memory at all? We seem
to be initialising most of struct page in __init_single_page(), so it
seems like a lot of additional complexity to conditionally zero the rest
of struct page.
Alternatively, just zero out the entire vmemmap area when it is setup
in the kernel page tables.
Hi Dave,
I can do this, either way is fine with me. It would be a little slower
compared to the current approach where we benefit from having memset()
to work as prefetch. But that would become negligible, once in the
future we will increase the granularity of multi-threading, currently it
is only one thread per-mnode to multithread vmemamp. Your call.
Thank you,
Pasha
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
