From: Mel Gorman <mgorman@suse.de>
To: Linux-MM <linux-mm@kvack.org>
Cc: Rik van Riel <riel@redhat.com>, Hugh Dickins <hughd@google.com>,
Minchan Kim <minchan@kernel.org>,
Dave Hansen <dave.hansen@intel.com>,
Andi Kleen <andi@firstfloor.org>,
LKML <linux-kernel@vger.kernel.org>, Mel Gorman <mgorman@suse.de>
Subject: [PATCH 6/6] mm: Gather more PFNs before sending a TLB to flush unmapped pages
Date: Tue, 21 Apr 2015 11:41:20 +0100 [thread overview]
Message-ID: <1429612880-21415-7-git-send-email-mgorman@suse.de> (raw)
In-Reply-To: <1429612880-21415-1-git-send-email-mgorman@suse.de>
The patch "mm: Send a single IPI to TLB flush multiple pages when unmapping"
would batch 32 pages before sending an IPI. This patch increases the size of
the data structure to hold a pages worth of PFNs before sending an IPI. This
is a trade-off between memory usage and reducing IPIS sent. In the ideal
case where multiple processes are reading large mapped files, this patch
reduces interrupts/second from roughly 180K per second to 60K per second.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
---
include/linux/sched.h | 9 +++++----
kernel/fork.c | 6 ++++--
mm/vmscan.c | 5 +++--
3 files changed, 12 insertions(+), 8 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5c09db02fe78..3e4d3f545005 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1275,16 +1275,17 @@ enum perf_event_task_context {
perf_nr_task_contexts,
};
-/* Matches SWAP_CLUSTER_MAX but refined to limit header dependencies */
-#define BATCH_TLBFLUSH_SIZE 32UL
-
/* Track pages that require TLB flushes */
struct tlbflush_unmap_batch {
struct cpumask cpumask;
unsigned long nr_pages;
- unsigned long pfns[BATCH_TLBFLUSH_SIZE];
+ unsigned long pfns[0];
};
+/* alloc_tlb_ubc() always allocates a page */
+#define BATCH_TLBFLUSH_SIZE \
+ ((PAGE_SIZE - sizeof(struct tlbflush_unmap_batch)) / sizeof(unsigned long))
+
struct task_struct {
volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */
void *stack;
diff --git a/kernel/fork.c b/kernel/fork.c
index 86c872fec9fb..f260663f209a 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -247,8 +247,10 @@ void __put_task_struct(struct task_struct *tsk)
put_signal_struct(tsk->signal);
#ifdef CONFIG_ARCH_SUPPORTS_LOCAL_TLB_PFN_FLUSH
- kfree(tsk->tlb_ubc);
- tsk->tlb_ubc = NULL;
+ if (tsk->tlb_ubc) {
+ free_page((unsigned long)tsk->tlb_ubc);
+ tsk->tlb_ubc = NULL;
+ }
#endif
if (!profile_handoff_task(tsk))
diff --git a/mm/vmscan.c b/mm/vmscan.c
index e39e7c4bf548..080ba929049c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2775,14 +2775,15 @@ out:
/*
* Allocate the control structure for batch TLB flushing. An allocation
* failure is harmless as the reclaimer will send IPIs where necessary.
+ * If the allocation size changes then update BATCH_TLBFLUSH_SIZE.
*/
void alloc_tlb_ubc(void)
{
if (current->tlb_ubc)
return;
- current->tlb_ubc = kmalloc(sizeof(struct tlbflush_unmap_batch),
- GFP_ATOMIC | __GFP_NOWARN);
+ current->tlb_ubc = (struct tlbflush_unmap_batch *)
+ __get_free_page(GFP_KERNEL | __GFP_NOWARN);
if (!current->tlb_ubc)
return;
--
2.1.2
next prev parent reply other threads:[~2015-04-21 10:41 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-21 10:41 [RFC PATCH 0/6] TLB flush multiple pages with a single IPI v3 Mel Gorman
2015-04-21 10:41 ` [PATCH 1/6] x86, mm: Trace when an IPI is about to be sent Mel Gorman
2015-04-21 10:41 ` [PATCH 2/6] mm: Send a single IPI to TLB flush multiple pages when unmapping Mel Gorman
2015-04-21 10:41 ` [PATCH 3/6] mm: Defer TLB flush after unmap as long as possible Mel Gorman
2015-04-21 20:31 ` Rik van Riel
2015-04-21 21:17 ` Mel Gorman
2015-04-21 10:41 ` [PATCH 4/6] mm, migrate: Drop references to successfully migrated pages at the same time Mel Gorman
2015-04-21 10:41 ` [PATCH 5/6] mm, migrate: Batch TLB flushing when unmapping pages for migration Mel Gorman
2015-04-21 10:41 ` Mel Gorman [this message]
2015-04-24 14:46 ` [RFC PATCH 0/6] TLB flush multiple pages with a single IPI v3 Vlastimil Babka
2015-04-24 15:16 ` Mel Gorman
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