[PATCH] revert the process-migration-speedup patch

David Mosberger asked that this be backed out:

"I do not believe that flushing the TLB before migration is be the right thing
to do on ia64 machines which support global TLB purges (i.e., all but SGI's
machines)."

It was of huge benefit for the SGI machines, so work is ongoing.

include/asm-generic/tlb.h

@@ -146,6 +146,4 @@ static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 		__pmd_free_tlb(tlb, pmdp);			\
 	} while (0)
 
-#define tlb_migrate_prepare(mm) do { } while(0)
-
 #endif /* _ASM_GENERIC__TLB_H */

include/asm-ia64/tlb.h

@@ -211,8 +211,6 @@ __tlb_remove_tlb_entry (struct mmu_gather *tlb, pte_t *ptep, unsigned long addre
 	tlb->end_addr = address + PAGE_SIZE;
 }
 
-#define tlb_migrate_prepare(mm) flush_tlb_mm(mm)
-
 #define tlb_start_vma(tlb, vma)			do { } while (0)
 #define tlb_end_vma(tlb, vma)			do { } while (0)
 

kernel/sched.c

@@ -26,8 +26,6 @@
 #include <linux/highmem.h>
 #include <linux/smp_lock.h>
 #include <asm/mmu_context.h>
-#include <linux//pagemap.h>
-#include <asm/tlb.h>
 #include <linux/interrupt.h>
 #include <linux/completion.h>
 #include <linux/kernel_stat.h>
@@ -1302,14 +1300,6 @@ static void sched_migrate_task(task_t *p, int dest_cpu)
 		wake_up_process(mt);
 		put_task_struct(mt);
 		wait_for_completion(&req.done);
-
-		/*
-		 * we want a new context here. This eliminates TLB
-		 * flushes on the cpus where the process executed prior to
-		 * the migration.
-		 */
-		tlb_migrate_prepare(current->mm);
-
 		return;
 	}
 out: