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| author | Rik van Riel <riel@surriel.com> | 2018-09-25 23:58:38 -0400 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2018-10-09 16:51:11 +0200 |
| commit | 5462bc3a9a3c38328bbbd276d51164c7cf21d6a8 (patch) | |
| tree | 2581f1146d6bfca6fec8a02a3133049950550ab6 /arch/x86/mm | |
| parent | a31acd3ee8f7dbc0370bdf4a4bfef7a8c13c7542 (diff) | |
| download | blackbird-op-linux-5462bc3a9a3c38328bbbd276d51164c7cf21d6a8.tar.gz blackbird-op-linux-5462bc3a9a3c38328bbbd276d51164c7cf21d6a8.zip | |
x86/mm/tlb: Always use lazy TLB mode
On most workloads, the number of context switches far exceeds the
number of TLB flushes sent. Optimizing the context switches, by always
using lazy TLB mode, speeds up those workloads.
This patch results in about a 1% reduction in CPU use on a two socket
Broadwell system running a memcache like workload.
Cc: npiggin@gmail.com
Cc: efault@gmx.de
Cc: will.deacon@arm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-team@fb.com
Cc: hpa@zytor.com
Cc: luto@kernel.org
Tested-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Rik van Riel <riel@surriel.com>
(cherry picked from commit 95b0e6357d3e4e05349668940d7ff8f3b7e7e11e)
Acked-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180716190337.26133-7-riel@surriel.com
Diffstat (limited to 'arch/x86/mm')
| -rw-r--r-- | arch/x86/mm/tlb.c | 15 |
1 files changed, 1 insertions, 14 deletions
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 6aa195796dec..54a5870190a6 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -368,20 +368,7 @@ void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk) if (this_cpu_read(cpu_tlbstate.loaded_mm) == &init_mm) return; - if (tlb_defer_switch_to_init_mm()) { - /* - * There's a significant optimization that may be possible - * here. We have accurate enough TLB flush tracking that we - * don't need to maintain coherence of TLB per se when we're - * lazy. We do, however, need to maintain coherence of - * paging-structure caches. We could, in principle, leave our - * old mm loaded and only switch to init_mm when - * tlb_remove_page() happens. - */ - this_cpu_write(cpu_tlbstate.is_lazy, true); - } else { - switch_mm(NULL, &init_mm, NULL); - } + this_cpu_write(cpu_tlbstate.is_lazy, true); } /* |
