[PATCH 00/22] Cleanup and optimise the page allocator V7

Mel Gorman
2009-04-22T13:54:32Z

Here is V7 of the cleanup and optimisation of the page allocator and
it should be ready for wider testing. Please consider a possibility for
merging as a Pass 1 at making the page allocator faster. Other passes will
occur later when this one has had a bit of exercise. This patchset is based
on mmotm-2009-04-17 and I've tested it successfully on a small number of
machines.

The performance improvements are in a wide range depending on the exact
machine but the results I've seen so fair are approximately;

kernbench: 0 to 0.12% (elapsed time)
0.49% to 3.20% (sys time)
aim9: -4% to 30% (for page_test and brk_test)
tbench: -1% to 4%
hackbench: -2.5% to 3.45% (mostly within the noise though)
netperf-udp -1.34% to 4.06% (varies between machines a bit)
netperf-tcp -0.44% to 5.22% (varies between machines a bit)

I haven't sysbench figures at hand, but previously they were within the -0.5%
to 2% range.

On netperf, the client and server were bound to opposite number CPUs to
maximise the problems with cache line bouncing of the struct pages so I
expect different people to report different results for netperf depending
on their exact machine and how they ran the test (different machines, same
cpus client/server, shared cache but two threads client/server, different
socket client/server etc).

I also measured the vmlinux sizes for a single x86-based config with
CONFIG_DEBUG_INFO enabled but not CONFIG_DEBUG_VM. The core of the .config
is based on the Debian Lenny kernel config so I expect it to be reasonably
typical.

text kernel
3355726 mmotm-20090417
3355718 0001-Replace-__alloc_pages_internal-with-__alloc_pages_.patch
3355622 0002-Do-not-sanity-check-order-in-the-fast-path.patch
3355574 0003-Do-not-check-NUMA-node-ID-when-the-caller-knows-the.patch
3355574 0004-Check-only-once-if-the-zonelist-is-suitable-for-the.patch
3355526 0005-Break-up-the-allocator-entry-point-into-fast-and-slo.patch
3355420 0006-Move-check-for-disabled-anti-fragmentation-out-of-fa.patch
3355452 0007-Calculate-the-preferred-zone-for-allocation-only-onc.patch
3355452 0008-Calculate-the-migratetype-for-allocation-only-once.patch
3355436 0009-Calculate-the-alloc_flags-for-allocation-only-once.patch
3355436 0010-Remove-a-branch-by-assuming-__GFP_HIGH-ALLOC_HIGH.patch
3355420 0011-Inline-__rmqueue_smallest.patch
3355420 0012-Inline-buffered_rmqueue.patch
3355420 0013-Inline-__rmqueue_fallback.patch
3355404 0014-Do-not-call-get_pageblock_migratetype-more-than-ne.patch
3355300 0015-Do-not-disable-interrupts-in-free_page_mlock.patch
3355300 0016-Do-not-setup-zonelist-cache-when-there-is-only-one-n.patch
3355188 0017-Do-not-check-for-compound-pages-during-the-page-allo.patch
3355161 0018-Use-allocation-flags-as-an-index-to-the-zone-waterma.patch
3355129 0019-Update-NR_FREE_PAGES-only-as-necessary.patch
3355129 0020-Get-the-pageblock-migratetype-without-disabling-inte.patch
3355129 0021-Use-a-pre-calculated-value-instead-of-num_online_nod.patch

Some patches were dropped in this revision because while I believe they
improved performance, they also increase the text size so they need to
be revisited in isolation to show they actually help things and by how
much. Other than that, the biggest changes were cleaning up accidental
functional changes identified by Kosaki Motohiro. Massive credit to him for a
very defailed review of V6, to Christoph Lameter who reviewed earlier versions
quite heavily and Pekka who kicked through V6 in quite a lot of detail.

arch/ia64/hp/common/sba_iommu.c | 2
arch/ia64/kernel/mca.c | 3
arch/ia64/kernel/uncached.c | 3
arch/ia64/sn/pci/pci_dma.c | 3
arch/powerpc/platforms/cell/ras.c | 2
arch/x86/kvm/vmx.c | 2
drivers/misc/sgi-gru/grufile.c | 2
drivers/misc/sgi-xp/xpc_uv.c | 2
include/linux/gfp.h | 27 -
include/linux/mm.h | 1
include/linux/mmzone.h | 11
include/linux/nodemask.h | 15 -
kernel/profile.c | 8
mm/filemap.c | 2
mm/hugetlb.c | 8
mm/internal.h | 11
mm/mempolicy.c | 2
mm/migrate.c | 2
mm/page_alloc.c | 555 ++++++++++++++++++++++++--------------
mm/slab.c | 11
mm/slob.c | 4
mm/slub.c | 2
net/sunrpc/svc.c | 2
23 files changed, 424 insertions(+), 256 deletions(-)

Changes since V6
o Remove unintentional functional changes when splitting into fast and slow paths
o Drop patch 7 for zonelist filtering as it modified when zlc_setup() is called
for the wrong reasons. The patch that avoids calling it for non-NUMA machines is
still there which has the bulk of the saving. cpusets is relatively small
o Drop an unnecessary check for in_interrupt() in gfp_to_alloc_flags()
o Clarify comment on __GFP_HIGH == ALLOC_HIGH
o Redefine the watermark mask to be expessed in terms of ALLOC_MARK_NOWATERMARK
o Use BUILD_BUG_ON for checking __GFP_HIGH == ALLOC_HIGH
o Drop some patches that were not reducing text sizes as expected
o Remove numa_platform from slab

Change since V5
o Rebase to mmotm-2009-04-17

Changes since V4
o Drop the more controversial patches for now and focus on the "obvious win"
material.
o Add reviewed-by notes
o Fix changelog entry to say __rmqueue_fallback instead __rmqueue
o Add unlikely() for the clearMlocked check
o Change where PGFREE is accounted in free_hot_cold_page() to have symmetry
with __free_pages_ok()
o Convert num_online_nodes() to use a static value so that callers do
not have to be individually updated
o Rebase to mmotm-2003-03-13

Changes since V3
o Drop the more controversial patches for now and focus on the "obvious win"
material
o Add reviewed-by notes
o Fix changelog entry to say __rmqueue_fallback instead __rmqueue
o Add unlikely() for the clearMlocked check
o Change where PGFREE is accounted in free_hot_cold_page() to have symmetry
with __free_pages_ok()

Changes since V2
o Remove brances by treating watermark flags as array indices
o Remove branch by assuming __GFP_HIGH == ALLOC_HIGH
o Do not check for compound on every page free
o Remove branch by always ensuring the migratetype is known on free
o Simplify buffered_rmqueue further
o Reintroduce improved version of batched bulk free of pcp pages
o Use allocation flags as an index to zone watermarks
o Work out __GFP_COLD only once
o Reduce the number of times zone stats are updated
o Do not dump reserve pages back into the allocator. Instead treat them
as MOVABLE so that MIGRATE_RESERVE gets used on the max-order-overlapped
boundaries without causing trouble
o Allow pages up to PAGE_ALLOC_COSTLY_ORDER to use the per-cpu allocator.
order-1 allocations are frequently enough in particular to justify this
o Rearrange inlining such that the hot-path is inlined but not in a way
that increases the text size of the page allocator
o Make the check for needing additional zonelist filtering due to NUMA
or cpusets as light as possible
o Do not destroy compound pages going to the PCP lists
o Delay the merging of buddies until a high-order allocation needs them
or anti-fragmentation is being forced to fallback

Changes since V1
o Remove the ifdef CONFIG_CPUSETS from inside get_page_from_freelist()
o Use non-lock bit operations for clearing the mlock flag
o Factor out alloc_flags calculation so it is only done once (Peter)
o Make gfp.h a bit prettier and clear-cut (Peter)
o Instead of deleting a debugging check, replace page_count() in the
free path with a version that does not check for compound pages (Nick)
o Drop the alteration for hot/cold page freeing until we know if it
helps or not