x86/mm: split vmalloc_sync_all()

Commit 3f8fd02b1b ("mm/vmalloc: Sync unmappings in
__purge_vmap_area_lazy()") introduced a call to vmalloc_sync_all() in
the vunmap() code-path.  While this change was necessary to maintain
correctness on x86-32-pae kernels, it also adds additional cycles for
architectures that don't need it.

Specifically on x86-64 with CONFIG_VMAP_STACK=y some people reported
severe performance regressions in micro-benchmarks because it now also
calls the x86-64 implementation of vmalloc_sync_all() on vunmap().  But
the vmalloc_sync_all() implementation on x86-64 is only needed for newly
created mappings.

To avoid the unnecessary work on x86-64 and to gain the performance
back, split up vmalloc_sync_all() into two functions:

	* vmalloc_sync_mappings(), and
	* vmalloc_sync_unmappings()

Most call-sites to vmalloc_sync_all() only care about new mappings being
synchronized.  The only exception is the new call-site added in the
above mentioned commit.

Shile Zhang directed us to a report of an 80% regression in reaim
throughput.

Fixes: 3f8fd02b1b ("mm/vmalloc: Sync unmappings in __purge_vmap_area_lazy()")
Reported-by: kernel test robot <oliver.sang@intel.com>
Reported-by: Shile Zhang <shile.zhang@linux.alibaba.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Borislav Petkov <bp@suse.de>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>	[GHES]
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20191009124418.8286-1-joro@8bytes.org
Link: https://lists.01.org/hyperkitty/list/lkp@lists.01.org/thread/4D3JPPHBNOSPFK2KEPC6KGKS6J25AIDB/
Link: http://lkml.kernel.org/r/20191113095530.228959-1-shile.zhang@linux.alibaba.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Joerg Roedel 2020-03-21 18:22:41 -07:00 committed by Linus Torvalds
parent 0715e6c516
commit 763802b53a
6 changed files with 43 additions and 13 deletions

View File

@ -190,7 +190,7 @@ static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
return pmd_k;
}
void vmalloc_sync_all(void)
static void vmalloc_sync(void)
{
unsigned long address;
@ -217,6 +217,16 @@ void vmalloc_sync_all(void)
}
}
void vmalloc_sync_mappings(void)
{
vmalloc_sync();
}
void vmalloc_sync_unmappings(void)
{
vmalloc_sync();
}
/*
* 32-bit:
*
@ -319,11 +329,23 @@ out:
#else /* CONFIG_X86_64: */
void vmalloc_sync_all(void)
void vmalloc_sync_mappings(void)
{
/*
* 64-bit mappings might allocate new p4d/pud pages
* that need to be propagated to all tasks' PGDs.
*/
sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
}
void vmalloc_sync_unmappings(void)
{
/*
* Unmappings never allocate or free p4d/pud pages.
* No work is required here.
*/
}
/*
* 64-bit:
*

View File

@ -171,7 +171,7 @@ int ghes_estatus_pool_init(int num_ghes)
* New allocation must be visible in all pgd before it can be found by
* an NMI allocating from the pool.
*/
vmalloc_sync_all();
vmalloc_sync_mappings();
rc = gen_pool_add(ghes_estatus_pool, addr, PAGE_ALIGN(len), -1);
if (rc)

View File

@ -141,8 +141,9 @@ extern int remap_vmalloc_range_partial(struct vm_area_struct *vma,
extern int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
unsigned long pgoff);
void vmalloc_sync_all(void);
void vmalloc_sync_mappings(void);
void vmalloc_sync_unmappings(void);
/*
* Lowlevel-APIs (not for driver use!)
*/

View File

@ -519,7 +519,7 @@ NOKPROBE_SYMBOL(notify_die);
int register_die_notifier(struct notifier_block *nb)
{
vmalloc_sync_all();
vmalloc_sync_mappings();
return atomic_notifier_chain_register(&die_chain, nb);
}
EXPORT_SYMBOL_GPL(register_die_notifier);

View File

@ -370,10 +370,14 @@ void vm_unmap_aliases(void)
EXPORT_SYMBOL_GPL(vm_unmap_aliases);
/*
* Implement a stub for vmalloc_sync_all() if the architecture chose not to
* have one.
* Implement a stub for vmalloc_sync_[un]mapping() if the architecture
* chose not to have one.
*/
void __weak vmalloc_sync_all(void)
void __weak vmalloc_sync_mappings(void)
{
}
void __weak vmalloc_sync_unmappings(void)
{
}

View File

@ -1295,7 +1295,7 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)
* First make sure the mappings are removed from all page-tables
* before they are freed.
*/
vmalloc_sync_all();
vmalloc_sync_unmappings();
/*
* TODO: to calculate a flush range without looping.
@ -3128,16 +3128,19 @@ int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
EXPORT_SYMBOL(remap_vmalloc_range);
/*
* Implement a stub for vmalloc_sync_all() if the architecture chose not to
* have one.
* Implement stubs for vmalloc_sync_[un]mappings () if the architecture chose
* not to have one.
*
* The purpose of this function is to make sure the vmalloc area
* mappings are identical in all page-tables in the system.
*/
void __weak vmalloc_sync_all(void)
void __weak vmalloc_sync_mappings(void)
{
}
void __weak vmalloc_sync_unmappings(void)
{
}
static int f(pte_t *pte, unsigned long addr, void *data)
{