(12/12/11 4:27 AM), KAMEZAWA Hiroyuki wrote:
On Mon, 12 Dec 2011 09:49:30 +0900
KAMEZAWA Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
On Fri, 9 Dec 2011 17:48:40 -0500
kosaki.motohiro@xxxxxxxxx wrote:
From: KOSAKI Motohiro<kosaki.motohiro@xxxxxxxxxxxxxx>
commit 297c5eee37 (mm: make the vma list be doubly linked) added
vm_prev member into vm_area_struct. Therefore we can simplify
find_vma_prev() by using it. Also, this change help to improve
page fault performance because it has strong locality of reference.
Signed-off-by: KOSAKI Motohiro<kosaki.motohiro@xxxxxxxxxxxxxx>
Reviewed-by: KAMEZAWA Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxxx>
Hmm, your work remind me of a patch I tried in past.
Here is a refleshed one...how do you think ?
==
From c0261936fc01322d06425731d33f38b2021e8067 Mon Sep 17 00:00:00 2001
From: KAMEZAWA Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxxx>
Date: Mon, 12 Dec 2011 18:31:19 +0900
Subject: [PATCH] per thread vma cache.
This is a toy patch. How do you think ?
This is a patch for per-thread mmap_cache without heavy atomic ops.
I'm sure overhead of find_vma() is pretty small in usual application
and this will not show good improvement. But I think, if we need
to have cache of vma, it should be per thread rather than per mm.
Agreed. per-thread is better.
This patch adds thread->mmap_cache, a pointer for vm_area_struct
and update it appropriately. Because we have no refcnt on vm_area_struct,
thread->mmap_cache may be a stale pointer. This patch detects stale
pointer by checking
- thread->mmap_cache is one of SLABs in vm_area_cachep.
- thread->mmap_cache->vm_mm == mm.
vma->vm_mm will be cleared before kmem_cache_free() by this patch.
Do you mean the cache can make mishit with unrelated vma when freed vma
was reused?
If so, it is most tricky part of this patch, I strongly hope you write
a comment more.
Thank you.
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