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mm: mmu_gather rework

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Rework the existing mmu_gather infrastructure.

The direct purpose of these patches was to allow preemptible mmu_gather,
but even without that I think these patches provide an improvement to the
status quo.

The first 9 patches rework the mmu_gather infrastructure.  For review
purpose I've split them into generic and per-arch patches with the last of
those a generic cleanup.

The next patch provides generic RCU page-table freeing, and the followup
is a patch converting s390 to use this.  I've also got 4 patches from
DaveM lined up (not included in this series) that uses this to implement
gup_fast() for sparc64.

Then there is one patch that extends the generic mmu_gather batching.

After that follow the mm preemptibility patches, these make part of the mm
a lot more preemptible.  It converts i_mmap_lock and anon_vma->lock to
mutexes which together with the mmu_gather rework makes mmu_gather
preemptible as well.

Making i_mmap_lock a mutex also enables a clean-up of the truncate code.

This also allows for preemptible mmu_notifiers, something that XPMEM I
think wants.

Furthermore, it removes the new and universially detested unmap_mutex.

This patch:

Remove the first obstacle towards a fully preemptible mmu_gather.

The current scheme assumes mmu_gather is always done with preemption
disabled and uses per-cpu storage for the page batches.  Change this to
try and allocate a page for batching and in case of failure, use a small
on-stack array to make some progress.

Preemptible mmu_gather is desired in general and usable once i_mmap_lock
becomes a mutex.  Doing it before the mutex conversion saves us from
having to rework the code by moving the mmu_gather bits inside the
pte_lock.

Also avoid flushing the tlb batches from under the pte lock, this is
useful even without the i_mmap_lock conversion as it significantly reduces
pte lock hold times.

[akpm@linux-foundation.org: fix comment tpyo]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Miller <davem@davemloft.net>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Tony Luck <tony.luck@intel.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Peter Zijlstra
2011-05-24 17:11:45 -07:00
committed by Linus Torvalds
parent d05f3169c0
commit d16dfc550f
5 changed files with 107 additions and 65 deletions
Download Patch File Download Diff File Expand all files Collapse all files

46
mm/memory.c
View File

@ -912,12 +912,13 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
long *zap_work, struct zap_details *details)
{
struct mm_struct *mm = tlb->mm;
int force_flush = 0;
pte_t *pte;
spinlock_t *ptl;
int rss[NR_MM_COUNTERS];
init_rss_vec(rss);
again:
pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
arch_enter_lazy_mmu_mode();
do {
@ -974,7 +975,9 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
page_remove_rmap(page);
if (unlikely(page_mapcount(page) < 0))
print_bad_pte(vma, addr, ptent, page);
tlb_remove_page(tlb, page);
force_flush = !__tlb_remove_page(tlb, page);
if (force_flush)
break;
continue;
}
/*
@ -1001,6 +1004,18 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
arch_leave_lazy_mmu_mode();
pte_unmap_unlock(pte - 1, ptl);
/*
* mmu_gather ran out of room to batch pages, we break out of
* the PTE lock to avoid doing the potential expensive TLB invalidate
* and page-free while holding it.
*/
if (force_flush) {
force_flush = 0;
tlb_flush_mmu(tlb);
if (addr != end)
goto again;
}
return addr;
}
@ -1121,17 +1136,14 @@ static unsigned long unmap_page_range(struct mmu_gather *tlb,
* ensure that any thus-far unmapped pages are flushed before unmap_vmas()
* drops the lock and schedules.
*/
unsigned long unmap_vmas(struct mmu_gather **tlbp,
unsigned long unmap_vmas(struct mmu_gather *tlb,
struct vm_area_struct *vma, unsigned long start_addr,
unsigned long end_addr, unsigned long *nr_accounted,
struct zap_details *details)
{
long zap_work = ZAP_BLOCK_SIZE;
unsigned long tlb_start = 0; /* For tlb_finish_mmu */
int tlb_start_valid = 0;
unsigned long start = start_addr;
spinlock_t *i_mmap_lock = details? details->i_mmap_lock: NULL;
int fullmm = (*tlbp)->fullmm;
struct mm_struct *mm = vma->vm_mm;
mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
@ -1152,11 +1164,6 @@ unsigned long unmap_vmas(struct mmu_gather **tlbp,
untrack_pfn_vma(vma, 0, 0);
while (start != end) {
if (!tlb_start_valid) {
tlb_start = start;
tlb_start_valid = 1;
}
if (unlikely(is_vm_hugetlb_page(vma))) {
/*
* It is undesirable to test vma->vm_file as it
@ -1177,7 +1184,7 @@ unsigned long unmap_vmas(struct mmu_gather **tlbp,
start = end;
} else
start = unmap_page_range(*tlbp, vma,
start = unmap_page_range(tlb, vma,
start, end, &zap_work, details);
if (zap_work > 0) {
@ -1185,19 +1192,13 @@ unsigned long unmap_vmas(struct mmu_gather **tlbp,
break;
}
tlb_finish_mmu(*tlbp, tlb_start, start);
if (need_resched() ||
(i_mmap_lock && spin_needbreak(i_mmap_lock))) {
if (i_mmap_lock) {
*tlbp = NULL;
if (i_mmap_lock)
goto out;
}
cond_resched();
}
*tlbp = tlb_gather_mmu(vma->vm_mm, fullmm);
tlb_start_valid = 0;
zap_work = ZAP_BLOCK_SIZE;
}
}
@ -1217,16 +1218,15 @@ unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
unsigned long size, struct zap_details *details)
{
struct mm_struct *mm = vma->vm_mm;
struct mmu_gather *tlb;
struct mmu_gather tlb;
unsigned long end = address + size;
unsigned long nr_accounted = 0;
lru_add_drain();
tlb = tlb_gather_mmu(mm, 0);
tlb_gather_mmu(&tlb, mm, 0);
update_hiwater_rss(mm);
end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
if (tlb)
tlb_finish_mmu(tlb, address, end);
tlb_finish_mmu(&tlb, address, end);
return end;
}