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 <[email protected]> --- include/linux/sched.h | 9 +++++---- kernel/fork.c | 6 ++++-- mm/vmscan.c | 13 +++++++------ 3 files changed, 16 insertions(+), 12 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 f668c8fa78fd..a8dde281652a 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2766,17 +2766,18 @@ out: } #ifdef CONFIG_ARCH_SUPPORTS_LOCAL_TLB_PFN_FLUSH +/* + * 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. + */ static inline void alloc_tlb_ubc(void) { if (current->tlb_ubc) return; - /* - * Allocate the control structure for batch TLB flushing. Harmless if - * the allocation fails as reclaimer will just send more IPIs. - */ - 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
