On Wed, Mar 15, 2017 at 03:56:02PM +0100, Vlastimil Babka wrote:
> I wonder if the difference would be larger if the parallelism was done
> on a higher level, something around unmap_page_range(). IIUC the current
I guess I misunderstand you in my last email - doing it at
unmap_page_range() level is essentially doing it at a per-VMA level
since it is the main function used in unmap_single_vma(). We have tried
that and felt that it's not flexible as the proposed approach since
it wouldn't parallize well for:
1 work load that uses only 1 or very few huge VMA;
2 work load that has a lot of small VMAs.
The code is nice and easy though(developed at v4.9 time frame):
>From f6d5cfde888b9e0356719fabe8754fdfe6fe236b Mon Sep 17 00:00:00 2001
From: Aaron Lu <aaron.lu@xxxxxxxxx>
Date: Wed, 11 Jan 2017 15:56:06 +0800
Subject: [PATCH] mm: async free vma
---
include/linux/mm_types.h | 6 ++++++
mm/memory.c | 23 ++++++++++++++++++++++-
2 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 4a8acedf4b7d..d10d2ce8f8f4 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -358,6 +358,12 @@ struct vm_area_struct {
struct mempolicy *vm_policy; /* NUMA policy for the VMA */
#endif
struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
+
+ struct vma_free_ctx {
+ unsigned long start_addr;
+ unsigned long end_addr;
+ struct work_struct work;
+ } free_ctx;
};
struct core_thread {
diff --git a/mm/memory.c b/mm/memory.c
index e18c57bdc75c..0fe4e45a044b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1345,6 +1345,17 @@ static void unmap_single_vma(struct mmu_gather *tlb,
}
}
+static void unmap_single_vma_work(struct work_struct *work)
+{
+ struct vma_free_ctx *ctx = container_of(work, struct vma_free_ctx, work);
+ struct vm_area_struct *vma = container_of(ctx, struct vm_area_struct, free_ctx);
+ struct mmu_gather tlb;
+
+ tlb_gather_mmu(&tlb, vma->vm_mm, ctx->start_addr, ctx->end_addr);
+ unmap_single_vma(&tlb, vma, ctx->start_addr, ctx->end_addr, NULL);
+ tlb_finish_mmu(&tlb, ctx->start_addr, ctx->end_addr);
+}
+
/**
* unmap_vmas - unmap a range of memory covered by a list of vma's
* @tlb: address of the caller's struct mmu_gather
@@ -1368,10 +1379,20 @@ void unmap_vmas(struct mmu_gather *tlb,
unsigned long end_addr)
{
struct mm_struct *mm = vma->vm_mm;
+ struct vma_free_ctx *ctx;
+ struct vm_area_struct *tmp = vma;
mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
+ for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next) {
+ ctx = &vma->free_ctx;
+ ctx->start_addr = start_addr;
+ ctx->end_addr = end_addr;
+ INIT_WORK(&ctx->work, unmap_single_vma_work);
+ queue_work(system_unbound_wq, &ctx->work);
+ }
+ vma = tmp;
for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next)
- unmap_single_vma(tlb, vma, start_addr, end_addr, NULL);
+ flush_work(&vma->free_ctx.work);
mmu_notifier_invalidate_range_end(mm, start_addr, end_addr);
}
--
2.9.3
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