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authorDaniel Jordan <daniel.m.jordan@oracle.com>2020-06-03 15:59:51 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-03 20:09:45 -0700
commite44431498f5fbf427f139aa413cf381b4fa3a600 (patch)
tree3648c163ba2117bcc60ffd391ab267e7e28413dc /mm/page_alloc.c
parent89c7c4022dfccf0c48ab22f4a6fd2db3d98fe3bc (diff)
mm: parallelize deferred_init_memmap()
Deferred struct page init is a significant bottleneck in kernel boot. Optimizing it maximizes availability for large-memory systems and allows spinning up short-lived VMs as needed without having to leave them running. It also benefits bare metal machines hosting VMs that are sensitive to downtime. In projects such as VMM Fast Restart[1], where guest state is preserved across kexec reboot, it helps prevent application and network timeouts in the guests. Multithread to take full advantage of system memory bandwidth. The maximum number of threads is capped at the number of CPUs on the node because speedups always improve with additional threads on every system tested, and at this phase of boot, the system is otherwise idle and waiting on page init to finish. Helper threads operate on section-aligned ranges to both avoid false sharing when setting the pageblock's migrate type and to avoid accessing uninitialized buddy pages, though max order alignment is enough for the latter. The minimum chunk size is also a section. There was benefit to using multiple threads even on relatively small memory (1G) systems, and this is the smallest size that the alignment allows. The time (milliseconds) is the slowest node to initialize since boot blocks until all nodes finish. intel_pstate is loaded in active mode without hwp and with turbo enabled, and intel_idle is active as well. Intel(R) Xeon(R) Platinum 8167M CPU @ 2.00GHz (Skylake, bare metal) 2 nodes * 26 cores * 2 threads = 104 CPUs 384G/node = 768G memory kernel boot deferred init ------------------------ ------------------------ node% (thr) speedup time_ms (stdev) speedup time_ms (stdev) ( 0) -- 4089.7 ( 8.1) -- 1785.7 ( 7.6) 2% ( 1) 1.7% 4019.3 ( 1.5) 3.8% 1717.7 ( 11.8) 12% ( 6) 34.9% 2662.7 ( 2.9) 79.9% 359.3 ( 0.6) 25% ( 13) 39.9% 2459.0 ( 3.6) 91.2% 157.0 ( 0.0) 37% ( 19) 39.2% 2485.0 ( 29.7) 90.4% 172.0 ( 28.6) 50% ( 26) 39.3% 2482.7 ( 25.7) 90.3% 173.7 ( 30.0) 75% ( 39) 39.0% 2495.7 ( 5.5) 89.4% 190.0 ( 1.0) 100% ( 52) 40.2% 2443.7 ( 3.8) 92.3% 138.0 ( 1.0) Intel(R) Xeon(R) CPU E5-2699C v4 @ 2.20GHz (Broadwell, kvm guest) 1 node * 16 cores * 2 threads = 32 CPUs 192G/node = 192G memory kernel boot deferred init ------------------------ ------------------------ node% (thr) speedup time_ms (stdev) speedup time_ms (stdev) ( 0) -- 1988.7 ( 9.6) -- 1096.0 ( 11.5) 3% ( 1) 1.1% 1967.0 ( 17.6) 0.3% 1092.7 ( 11.0) 12% ( 4) 41.1% 1170.3 ( 14.2) 73.8% 287.0 ( 3.6) 25% ( 8) 47.1% 1052.7 ( 21.9) 83.9% 177.0 ( 13.5) 38% ( 12) 48.9% 1016.3 ( 12.1) 86.8% 144.7 ( 1.5) 50% ( 16) 48.9% 1015.7 ( 8.1) 87.8% 134.0 ( 4.4) 75% ( 24) 49.1% 1012.3 ( 3.1) 88.1% 130.3 ( 2.3) 100% ( 32) 49.5% 1004.0 ( 5.3) 88.5% 125.7 ( 2.1) Intel(R) Xeon(R) CPU E5-2699 v3 @ 2.30GHz (Haswell, bare metal) 2 nodes * 18 cores * 2 threads = 72 CPUs 128G/node = 256G memory kernel boot deferred init ------------------------ ------------------------ node% (thr) speedup time_ms (stdev) speedup time_ms (stdev) ( 0) -- 1680.0 ( 4.6) -- 627.0 ( 4.0) 3% ( 1) 0.3% 1675.7 ( 4.5) -0.2% 628.0 ( 3.6) 11% ( 4) 25.6% 1250.7 ( 2.1) 67.9% 201.0 ( 0.0) 25% ( 9) 30.7% 1164.0 ( 17.3) 81.8% 114.3 ( 17.7) 36% ( 13) 31.4% 1152.7 ( 10.8) 84.0% 100.3 ( 17.9) 50% ( 18) 31.5% 1150.7 ( 9.3) 83.9% 101.0 ( 14.1) 75% ( 27) 31.7% 1148.0 ( 5.6) 84.5% 97.3 ( 6.4) 100% ( 36) 32.0% 1142.3 ( 4.0) 85.6% 90.0 ( 1.0) AMD EPYC 7551 32-Core Processor (Zen, kvm guest) 1 node * 8 cores * 2 threads = 16 CPUs 64G/node = 64G memory kernel boot deferred init ------------------------ ------------------------ node% (thr) speedup time_ms (stdev) speedup time_ms (stdev) ( 0) -- 1029.3 ( 25.1) -- 240.7 ( 1.5) 6% ( 1) -0.6% 1036.0 ( 7.8) -2.2% 246.0 ( 0.0) 12% ( 2) 11.8% 907.7 ( 8.6) 44.7% 133.0 ( 1.0) 25% ( 4) 13.9% 886.0 ( 10.6) 62.6% 90.0 ( 6.0) 38% ( 6) 17.8% 845.7 ( 14.2) 69.1% 74.3 ( 3.8) 50% ( 8) 16.8% 856.0 ( 22.1) 72.9% 65.3 ( 5.7) 75% ( 12) 15.4% 871.0 ( 29.2) 79.8% 48.7 ( 7.4) 100% ( 16) 21.0% 813.7 ( 21.0) 80.5% 47.0 ( 5.2) Server-oriented distros that enable deferred page init sometimes run in small VMs, and they still benefit even though the fraction of boot time saved is smaller: AMD EPYC 7551 32-Core Processor (Zen, kvm guest) 1 node * 2 cores * 2 threads = 4 CPUs 16G/node = 16G memory kernel boot deferred init ------------------------ ------------------------ node% (thr) speedup time_ms (stdev) speedup time_ms (stdev) ( 0) -- 716.0 ( 14.0) -- 49.7 ( 0.6) 25% ( 1) 1.8% 703.0 ( 5.3) -4.0% 51.7 ( 0.6) 50% ( 2) 1.6% 704.7 ( 1.2) 43.0% 28.3 ( 0.6) 75% ( 3) 2.7% 696.7 ( 13.1) 49.7% 25.0 ( 0.0) 100% ( 4) 4.1% 687.0 ( 10.4) 55.7% 22.0 ( 0.0) Intel(R) Xeon(R) CPU E5-2699 v3 @ 2.30GHz (Haswell, kvm guest) 1 node * 2 cores * 2 threads = 4 CPUs 14G/node = 14G memory kernel boot deferred init ------------------------ ------------------------ node% (thr) speedup time_ms (stdev) speedup time_ms (stdev) ( 0) -- 787.7 ( 6.4) -- 122.3 ( 0.6) 25% ( 1) 0.2% 786.3 ( 10.8) -2.5% 125.3 ( 2.1) 50% ( 2) 5.9% 741.0 ( 13.9) 37.6% 76.3 ( 19.7) 75% ( 3) 8.3% 722.0 ( 19.0) 49.9% 61.3 ( 3.2) 100% ( 4) 9.3% 714.7 ( 9.5) 56.4% 53.3 ( 1.5) On Josh's 96-CPU and 192G memory system: Without this patch series: [ 0.487132] node 0 initialised, 23398907 pages in 292ms [ 0.499132] node 1 initialised, 24189223 pages in 304ms ... [ 0.629376] Run /sbin/init as init process With this patch series: [ 0.231435] node 1 initialised, 24189223 pages in 32ms [ 0.236718] node 0 initialised, 23398907 pages in 36ms [1] https://static.sched.com/hosted_files/kvmforum2019/66/VMM-fast-restart_kvmforum2019.pdf Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Tested-by: Josh Triplett <josh@joshtriplett.org> Reviewed-by: Alexander Duyck <alexander.h.duyck@linux.intel.com> Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Hildenbrand <david@redhat.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Kirill Tkhai <ktkhai@virtuozzo.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Pavel Machek <pavel@ucw.cz> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Robert Elliott <elliott@hpe.com> Cc: Shile Zhang <shile.zhang@linux.alibaba.com> Cc: Steffen Klassert <steffen.klassert@secunet.com> Cc: Steven Sistare <steven.sistare@oracle.com> Cc: Tejun Heo <tj@kernel.org> Cc: Zi Yan <ziy@nvidia.com> Link: http://lkml.kernel.org/r/20200527173608.2885243-7-daniel.m.jordan@oracle.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c46
1 files changed, 40 insertions, 6 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 89bd57241e08..27ec5dc4db33 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -68,6 +68,7 @@
#include <linux/lockdep.h>
#include <linux/nmi.h>
#include <linux/psi.h>
+#include <linux/padata.h>
#include <asm/sections.h>
#include <asm/tlbflush.h>
@@ -1815,6 +1816,26 @@ deferred_init_maxorder(u64 *i, struct zone *zone, unsigned long *start_pfn,
return nr_pages;
}
+static void __init
+deferred_init_memmap_chunk(unsigned long start_pfn, unsigned long end_pfn,
+ void *arg)
+{
+ unsigned long spfn, epfn;
+ struct zone *zone = arg;
+ u64 i;
+
+ deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn, start_pfn);
+
+ /*
+ * Initialize and free pages in MAX_ORDER sized increments so that we
+ * can avoid introducing any issues with the buddy allocator.
+ */
+ while (spfn < end_pfn) {
+ deferred_init_maxorder(&i, zone, &spfn, &epfn);
+ cond_resched();
+ }
+}
+
/* Initialise remaining memory on a node */
static int __init deferred_init_memmap(void *data)
{
@@ -1824,7 +1845,7 @@ static int __init deferred_init_memmap(void *data)
unsigned long first_init_pfn, flags;
unsigned long start = jiffies;
struct zone *zone;
- int zid;
+ int zid, max_threads;
u64 i;
/* Bind memory initialisation thread to a local node if possible */
@@ -1864,13 +1885,26 @@ static int __init deferred_init_memmap(void *data)
goto zone_empty;
/*
- * Initialize and free pages in MAX_ORDER sized increments so
- * that we can avoid introducing any issues with the buddy
- * allocator.
+ * More CPUs always led to greater speedups on tested systems, up to
+ * all the nodes' CPUs. Use all since the system is otherwise idle now.
*/
+ max_threads = max(cpumask_weight(cpumask), 1u);
+
while (spfn < epfn) {
- deferred_init_maxorder(&i, zone, &spfn, &epfn);
- cond_resched();
+ unsigned long epfn_align = ALIGN(epfn, PAGES_PER_SECTION);
+ struct padata_mt_job job = {
+ .thread_fn = deferred_init_memmap_chunk,
+ .fn_arg = zone,
+ .start = spfn,
+ .size = epfn_align - spfn,
+ .align = PAGES_PER_SECTION,
+ .min_chunk = PAGES_PER_SECTION,
+ .max_threads = max_threads,
+ };
+
+ padata_do_multithreaded(&job);
+ deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn,
+ epfn_align);
}
zone_empty:
/* Sanity check that the next zone really is unpopulated */