[PATCH v2 0/3] xen/mm: Optimize init_heap_pages()

From: Julien Grall <julien@xen.org>
To: xen-devel@lists.xenproject.org
Cc: julien@xen.org, Julien Grall <jgrall@amazon.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	George Dunlap <george.dunlap@citrix.com>,
	Jan Beulich <jbeulich@suse.com>,
	Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>
Subject: [PATCH v2 0/3] xen/mm: Optimize init_heap_pages()
Date: Fri, 15 Jul 2022 18:03:09 +0100	[thread overview]
Message-ID: <20220715170312.13931-1-julien@xen.org> (raw)

From: Julien Grall <jgrall@amazon.com>

Hi all,

As part of the Live-Update work, we noticed that a big part Xen boot
is spent to add pages in the heap. For instance, on when running Xen
in a nested envionment on a c5.metal with 90GB, it takes ~1.4s.

This small series is reworking init_heap_pages() to give the pages
to free_heap_pages() by chunk rather than one by one.

With this approach, the time spent to init the heap is down
to 96 ms in the setup mention above.

There is potentially one more optimization possible that would
allow to further reduce the time spent. The new approach is accessing
the page information multiple time in separate loop that can potentially
be large.

Cheers,

Julien Grall (2):
  xen: page_alloc: Don't open-code IS_ALIGNED()
  xen/heap: Split init_heap_pages() in two
  xen/heap: pass order to free_heap_pages() in heap init

 xen/common/page_alloc.c | 106 ++++++++++++++++++++++++++++++----------
 1 file changed, 79 insertions(+), 27 deletions(-)

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2.32.0