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mm, x86/mm: Make the batched unmap TLB flush API more generic 

try_to_unmap_flush() used to open-code a rather x86-centric flush
sequence: local_flush_tlb() + flush_tlb_others().  Rearrange the
code so that the arch (only x86 for now) provides
arch_tlbbatch_add_mm() and arch_tlbbatch_flush() and the core code
calls those functions instead.

I'll want this for x86 because, to enable address space ids, I can't
support the flush_tlb_others() mode used by exising
try_to_unmap_flush() implementation with good performance.  I can
support the new API fairly easily, though.

I imagine that other architectures may be in a similar position.
Architectures with strong remote flush primitives (arm64?) may have
even worse performance problems with flush_tlb_others() the way that
try_to_unmap_flush() uses it.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/19f25a8581f9fb77876b7ff3b001f89835e34ea3.1495492063.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2017-05-22 15:30:03 -07:00 committed by Ingo Molnar
parent b3b90e5af7
commit e73ad5ff2f
5 changed files with 54 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
arch/x86/include/asm/tlbbatch.h Normal file
View File

@ -0,0 +1,16 @@
#ifndef _ARCH_X86_TLBBATCH_H
#define _ARCH_X86_TLBBATCH_H
#include <linux/cpumask.h>
#ifdef CONFIG_SMP
struct arch_tlbflush_unmap_batch {
/*
* Each bit set is a CPU that potentially has a TLB entry for one of
* the PFNs being flushed..
*/
struct cpumask cpumask;
};
#endif
#endif /* _ARCH_X86_TLBBATCH_H */

8
arch/x86/include/asm/tlbflush.h
View File

@ -329,6 +329,14 @@ static inline void reset_lazy_tlbstate(void)
this_cpu_write(cpu_tlbstate.active_mm, &init_mm);
}
static inline void arch_tlbbatch_add_mm(struct arch_tlbflush_unmap_batch *batch,
struct mm_struct *mm)
{
cpumask_or(&batch->cpumask, &batch->cpumask, mm_cpumask(mm));
}
extern void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch);
#endif /* SMP */
#ifndef CONFIG_PARAVIRT

17
arch/x86/mm/tlb.c
View File

@ -395,6 +395,23 @@ void flush_tlb_kernel_range(unsigned long start, unsigned long end)
}
}
void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch)
{
int cpu = get_cpu();
if (cpumask_test_cpu(cpu, &batch->cpumask)) {
count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
local_flush_tlb();
trace_tlb_flush(TLB_LOCAL_SHOOTDOWN, TLB_FLUSH_ALL);
}
if (cpumask_any_but(&batch->cpumask, cpu) < nr_cpu_ids)
flush_tlb_others(&batch->cpumask, NULL, 0, TLB_FLUSH_ALL);
cpumask_clear(&batch->cpumask);
put_cpu();
}
static ssize_t tlbflush_read_file(struct file *file, char __user *user_buf,
size_t count, loff_t *ppos)
{

15
include/linux/mm_types_task.h
View File

@ -14,6 +14,10 @@
#include <asm/page.h>
#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
#include <asm/tlbbatch.h>
#endif
#define USE_SPLIT_PTE_PTLOCKS (NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS)
#define USE_SPLIT_PMD_PTLOCKS (USE_SPLIT_PTE_PTLOCKS && \
IS_ENABLED(CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK))
@ -67,12 +71,15 @@ struct page_frag {
struct tlbflush_unmap_batch {
#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
/*
* Each bit set is a CPU that potentially has a TLB entry for one of
* the PFNs being flushed. See set_tlb_ubc_flush_pending().
* The arch code makes the following promise: generic code can modify a
* PTE, then call arch_tlbbatch_add_mm() (which internally provides all
* needed barriers), then call arch_tlbbatch_flush(), and the entries
* will be flushed on all CPUs by the time that arch_tlbbatch_flush()
* returns.
*/
struct cpumask cpumask;
struct arch_tlbflush_unmap_batch arch;
/* True if any bit in cpumask is set */
/* True if a flush is needed. */
bool flush_required;
/*

16
mm/rmap.c
View File

@ -579,25 +579,13 @@ void page_unlock_anon_vma_read(struct anon_vma *anon_vma)
void try_to_unmap_flush(void)
{
struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
int cpu;
if (!tlb_ubc->flush_required)
return;
cpu = get_cpu();
if (cpumask_test_cpu(cpu, &tlb_ubc->cpumask)) {
count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
local_flush_tlb();
trace_tlb_flush(TLB_LOCAL_SHOOTDOWN, TLB_FLUSH_ALL);
}
if (cpumask_any_but(&tlb_ubc->cpumask, cpu) < nr_cpu_ids)
flush_tlb_others(&tlb_ubc->cpumask, NULL, 0, TLB_FLUSH_ALL);
cpumask_clear(&tlb_ubc->cpumask);
arch_tlbbatch_flush(&tlb_ubc->arch);
tlb_ubc->flush_required = false;
tlb_ubc->writable = false;
put_cpu();
}
/* Flush iff there are potentially writable TLB entries that can race with IO */
@ -613,7 +601,7 @@ static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
{
struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
cpumask_or(&tlb_ubc->cpumask, &tlb_ubc->cpumask, mm_cpumask(mm));
arch_tlbbatch_add_mm(&tlb_ubc->arch, mm);
tlb_ubc->flush_required = true;
/*