mirror of
https://github.com/torvalds/linux.git
synced 2024-12-08 03:52:16 +00:00
e61abd4490
In tlb_batch_pages_flush(), we can end up freeing up to 512 pages or now up to 256 folio fragments that span more than one page, before we conditionally reschedule. It's a pain that we have to handle cond_resched() in tlb_batch_pages_flush() manually and cannot simply handle it in release_pages() -- release_pages() can be called from atomic context. Well, in a perfect world we wouldn't have to make our code more complicated at all. With page poisoning and init_on_free, we might now run into soft lockups when we free a lot of rather large folio fragments, because page freeing time then depends on the actual memory size we are freeing instead of on the number of folios that are involved. In the absolute (unlikely) worst case, on arm64 with 64k we will be able to free up to 256 folio fragments that each span 512 MiB: zeroing out 128 GiB does sound like it might take a while. But instead of ignoring this unlikely case, let's just handle it. So, let's teach tlb_batch_pages_flush() that there are some configurations where page freeing is horribly slow, and let's reschedule more frequently -- similarly like we did for now before we had large folio fragments in there. Avoid yet another loop over all encoded pages in the common case by handling that separately. Note that with page poisoning/zeroing, we might now end up freeing only a single folio fragment at a time that might exceed the old 512 pages limit: but if we cannot even free a single MAX_ORDER page on a system without running into soft lockups, something else is already completely bogus. Freeing a PMD-mapped THP would similarly cause trouble. In theory, we might even free 511 order-0 pages + a single MAX_ORDER page, effectively having to zero out 8703 pages on arm64 with 64k, translating to ~544 MiB of memory: however, if 512 MiB doesn't result in soft lockups, 544 MiB is unlikely to result in soft lockups, so we won't care about that for the time being. In the future, we might want to detect if handling cond_resched() is required at all, and just not do any of that with full preemption enabled. Link: https://lkml.kernel.org/r/20240214204435.167852-10-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Michal Hocko <mhocko@suse.com> Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Will Deacon <will@kernel.org> Cc: Yin Fengwei <fengwei.yin@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
472 lines
12 KiB
C
472 lines
12 KiB
C
#include <linux/gfp.h>
|
|
#include <linux/highmem.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/mmdebug.h>
|
|
#include <linux/mm_types.h>
|
|
#include <linux/mm_inline.h>
|
|
#include <linux/pagemap.h>
|
|
#include <linux/rcupdate.h>
|
|
#include <linux/smp.h>
|
|
#include <linux/swap.h>
|
|
#include <linux/rmap.h>
|
|
|
|
#include <asm/pgalloc.h>
|
|
#include <asm/tlb.h>
|
|
|
|
#ifndef CONFIG_MMU_GATHER_NO_GATHER
|
|
|
|
static bool tlb_next_batch(struct mmu_gather *tlb)
|
|
{
|
|
struct mmu_gather_batch *batch;
|
|
|
|
/* Limit batching if we have delayed rmaps pending */
|
|
if (tlb->delayed_rmap && tlb->active != &tlb->local)
|
|
return false;
|
|
|
|
batch = tlb->active;
|
|
if (batch->next) {
|
|
tlb->active = batch->next;
|
|
return true;
|
|
}
|
|
|
|
if (tlb->batch_count == MAX_GATHER_BATCH_COUNT)
|
|
return false;
|
|
|
|
batch = (void *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
|
|
if (!batch)
|
|
return false;
|
|
|
|
tlb->batch_count++;
|
|
batch->next = NULL;
|
|
batch->nr = 0;
|
|
batch->max = MAX_GATHER_BATCH;
|
|
|
|
tlb->active->next = batch;
|
|
tlb->active = batch;
|
|
|
|
return true;
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
static void tlb_flush_rmap_batch(struct mmu_gather_batch *batch, struct vm_area_struct *vma)
|
|
{
|
|
struct encoded_page **pages = batch->encoded_pages;
|
|
|
|
for (int i = 0; i < batch->nr; i++) {
|
|
struct encoded_page *enc = pages[i];
|
|
|
|
if (encoded_page_flags(enc) & ENCODED_PAGE_BIT_DELAY_RMAP) {
|
|
struct page *page = encoded_page_ptr(enc);
|
|
unsigned int nr_pages = 1;
|
|
|
|
if (unlikely(encoded_page_flags(enc) &
|
|
ENCODED_PAGE_BIT_NR_PAGES_NEXT))
|
|
nr_pages = encoded_nr_pages(pages[++i]);
|
|
|
|
folio_remove_rmap_ptes(page_folio(page), page, nr_pages,
|
|
vma);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* tlb_flush_rmaps - do pending rmap removals after we have flushed the TLB
|
|
* @tlb: the current mmu_gather
|
|
* @vma: The memory area from which the pages are being removed.
|
|
*
|
|
* Note that because of how tlb_next_batch() above works, we will
|
|
* never start multiple new batches with pending delayed rmaps, so
|
|
* we only need to walk through the current active batch and the
|
|
* original local one.
|
|
*/
|
|
void tlb_flush_rmaps(struct mmu_gather *tlb, struct vm_area_struct *vma)
|
|
{
|
|
if (!tlb->delayed_rmap)
|
|
return;
|
|
|
|
tlb_flush_rmap_batch(&tlb->local, vma);
|
|
if (tlb->active != &tlb->local)
|
|
tlb_flush_rmap_batch(tlb->active, vma);
|
|
tlb->delayed_rmap = 0;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* We might end up freeing a lot of pages. Reschedule on a regular
|
|
* basis to avoid soft lockups in configurations without full
|
|
* preemption enabled. The magic number of 512 folios seems to work.
|
|
*/
|
|
#define MAX_NR_FOLIOS_PER_FREE 512
|
|
|
|
static void __tlb_batch_free_encoded_pages(struct mmu_gather_batch *batch)
|
|
{
|
|
struct encoded_page **pages = batch->encoded_pages;
|
|
unsigned int nr, nr_pages;
|
|
|
|
while (batch->nr) {
|
|
if (!page_poisoning_enabled_static() && !want_init_on_free()) {
|
|
nr = min(MAX_NR_FOLIOS_PER_FREE, batch->nr);
|
|
|
|
/*
|
|
* Make sure we cover page + nr_pages, and don't leave
|
|
* nr_pages behind when capping the number of entries.
|
|
*/
|
|
if (unlikely(encoded_page_flags(pages[nr - 1]) &
|
|
ENCODED_PAGE_BIT_NR_PAGES_NEXT))
|
|
nr++;
|
|
} else {
|
|
/*
|
|
* With page poisoning and init_on_free, the time it
|
|
* takes to free memory grows proportionally with the
|
|
* actual memory size. Therefore, limit based on the
|
|
* actual memory size and not the number of involved
|
|
* folios.
|
|
*/
|
|
for (nr = 0, nr_pages = 0;
|
|
nr < batch->nr && nr_pages < MAX_NR_FOLIOS_PER_FREE;
|
|
nr++) {
|
|
if (unlikely(encoded_page_flags(pages[nr]) &
|
|
ENCODED_PAGE_BIT_NR_PAGES_NEXT))
|
|
nr_pages += encoded_nr_pages(pages[++nr]);
|
|
else
|
|
nr_pages++;
|
|
}
|
|
}
|
|
|
|
free_pages_and_swap_cache(pages, nr);
|
|
pages += nr;
|
|
batch->nr -= nr;
|
|
|
|
cond_resched();
|
|
}
|
|
}
|
|
|
|
static void tlb_batch_pages_flush(struct mmu_gather *tlb)
|
|
{
|
|
struct mmu_gather_batch *batch;
|
|
|
|
for (batch = &tlb->local; batch && batch->nr; batch = batch->next)
|
|
__tlb_batch_free_encoded_pages(batch);
|
|
tlb->active = &tlb->local;
|
|
}
|
|
|
|
static void tlb_batch_list_free(struct mmu_gather *tlb)
|
|
{
|
|
struct mmu_gather_batch *batch, *next;
|
|
|
|
for (batch = tlb->local.next; batch; batch = next) {
|
|
next = batch->next;
|
|
free_pages((unsigned long)batch, 0);
|
|
}
|
|
tlb->local.next = NULL;
|
|
}
|
|
|
|
static bool __tlb_remove_folio_pages_size(struct mmu_gather *tlb,
|
|
struct page *page, unsigned int nr_pages, bool delay_rmap,
|
|
int page_size)
|
|
{
|
|
int flags = delay_rmap ? ENCODED_PAGE_BIT_DELAY_RMAP : 0;
|
|
struct mmu_gather_batch *batch;
|
|
|
|
VM_BUG_ON(!tlb->end);
|
|
|
|
#ifdef CONFIG_MMU_GATHER_PAGE_SIZE
|
|
VM_WARN_ON(tlb->page_size != page_size);
|
|
VM_WARN_ON_ONCE(nr_pages != 1 && page_size != PAGE_SIZE);
|
|
VM_WARN_ON_ONCE(page_folio(page) != page_folio(page + nr_pages - 1));
|
|
#endif
|
|
|
|
batch = tlb->active;
|
|
/*
|
|
* Add the page and check if we are full. If so
|
|
* force a flush.
|
|
*/
|
|
if (likely(nr_pages == 1)) {
|
|
batch->encoded_pages[batch->nr++] = encode_page(page, flags);
|
|
} else {
|
|
flags |= ENCODED_PAGE_BIT_NR_PAGES_NEXT;
|
|
batch->encoded_pages[batch->nr++] = encode_page(page, flags);
|
|
batch->encoded_pages[batch->nr++] = encode_nr_pages(nr_pages);
|
|
}
|
|
/*
|
|
* Make sure that we can always add another "page" + "nr_pages",
|
|
* requiring two entries instead of only a single one.
|
|
*/
|
|
if (batch->nr >= batch->max - 1) {
|
|
if (!tlb_next_batch(tlb))
|
|
return true;
|
|
batch = tlb->active;
|
|
}
|
|
VM_BUG_ON_PAGE(batch->nr > batch->max - 1, page);
|
|
|
|
return false;
|
|
}
|
|
|
|
bool __tlb_remove_folio_pages(struct mmu_gather *tlb, struct page *page,
|
|
unsigned int nr_pages, bool delay_rmap)
|
|
{
|
|
return __tlb_remove_folio_pages_size(tlb, page, nr_pages, delay_rmap,
|
|
PAGE_SIZE);
|
|
}
|
|
|
|
bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page,
|
|
bool delay_rmap, int page_size)
|
|
{
|
|
return __tlb_remove_folio_pages_size(tlb, page, 1, delay_rmap, page_size);
|
|
}
|
|
|
|
#endif /* MMU_GATHER_NO_GATHER */
|
|
|
|
#ifdef CONFIG_MMU_GATHER_TABLE_FREE
|
|
|
|
static void __tlb_remove_table_free(struct mmu_table_batch *batch)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < batch->nr; i++)
|
|
__tlb_remove_table(batch->tables[i]);
|
|
|
|
free_page((unsigned long)batch);
|
|
}
|
|
|
|
#ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE
|
|
|
|
/*
|
|
* Semi RCU freeing of the page directories.
|
|
*
|
|
* This is needed by some architectures to implement software pagetable walkers.
|
|
*
|
|
* gup_fast() and other software pagetable walkers do a lockless page-table
|
|
* walk and therefore needs some synchronization with the freeing of the page
|
|
* directories. The chosen means to accomplish that is by disabling IRQs over
|
|
* the walk.
|
|
*
|
|
* Architectures that use IPIs to flush TLBs will then automagically DTRT,
|
|
* since we unlink the page, flush TLBs, free the page. Since the disabling of
|
|
* IRQs delays the completion of the TLB flush we can never observe an already
|
|
* freed page.
|
|
*
|
|
* Architectures that do not have this (PPC) need to delay the freeing by some
|
|
* other means, this is that means.
|
|
*
|
|
* What we do is batch the freed directory pages (tables) and RCU free them.
|
|
* We use the sched RCU variant, as that guarantees that IRQ/preempt disabling
|
|
* holds off grace periods.
|
|
*
|
|
* However, in order to batch these pages we need to allocate storage, this
|
|
* allocation is deep inside the MM code and can thus easily fail on memory
|
|
* pressure. To guarantee progress we fall back to single table freeing, see
|
|
* the implementation of tlb_remove_table_one().
|
|
*
|
|
*/
|
|
|
|
static void tlb_remove_table_smp_sync(void *arg)
|
|
{
|
|
/* Simply deliver the interrupt */
|
|
}
|
|
|
|
void tlb_remove_table_sync_one(void)
|
|
{
|
|
/*
|
|
* This isn't an RCU grace period and hence the page-tables cannot be
|
|
* assumed to be actually RCU-freed.
|
|
*
|
|
* It is however sufficient for software page-table walkers that rely on
|
|
* IRQ disabling.
|
|
*/
|
|
smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
|
|
}
|
|
|
|
static void tlb_remove_table_rcu(struct rcu_head *head)
|
|
{
|
|
__tlb_remove_table_free(container_of(head, struct mmu_table_batch, rcu));
|
|
}
|
|
|
|
static void tlb_remove_table_free(struct mmu_table_batch *batch)
|
|
{
|
|
call_rcu(&batch->rcu, tlb_remove_table_rcu);
|
|
}
|
|
|
|
#else /* !CONFIG_MMU_GATHER_RCU_TABLE_FREE */
|
|
|
|
static void tlb_remove_table_free(struct mmu_table_batch *batch)
|
|
{
|
|
__tlb_remove_table_free(batch);
|
|
}
|
|
|
|
#endif /* CONFIG_MMU_GATHER_RCU_TABLE_FREE */
|
|
|
|
/*
|
|
* If we want tlb_remove_table() to imply TLB invalidates.
|
|
*/
|
|
static inline void tlb_table_invalidate(struct mmu_gather *tlb)
|
|
{
|
|
if (tlb_needs_table_invalidate()) {
|
|
/*
|
|
* Invalidate page-table caches used by hardware walkers. Then
|
|
* we still need to RCU-sched wait while freeing the pages
|
|
* because software walkers can still be in-flight.
|
|
*/
|
|
tlb_flush_mmu_tlbonly(tlb);
|
|
}
|
|
}
|
|
|
|
static void tlb_remove_table_one(void *table)
|
|
{
|
|
tlb_remove_table_sync_one();
|
|
__tlb_remove_table(table);
|
|
}
|
|
|
|
static void tlb_table_flush(struct mmu_gather *tlb)
|
|
{
|
|
struct mmu_table_batch **batch = &tlb->batch;
|
|
|
|
if (*batch) {
|
|
tlb_table_invalidate(tlb);
|
|
tlb_remove_table_free(*batch);
|
|
*batch = NULL;
|
|
}
|
|
}
|
|
|
|
void tlb_remove_table(struct mmu_gather *tlb, void *table)
|
|
{
|
|
struct mmu_table_batch **batch = &tlb->batch;
|
|
|
|
if (*batch == NULL) {
|
|
*batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
|
|
if (*batch == NULL) {
|
|
tlb_table_invalidate(tlb);
|
|
tlb_remove_table_one(table);
|
|
return;
|
|
}
|
|
(*batch)->nr = 0;
|
|
}
|
|
|
|
(*batch)->tables[(*batch)->nr++] = table;
|
|
if ((*batch)->nr == MAX_TABLE_BATCH)
|
|
tlb_table_flush(tlb);
|
|
}
|
|
|
|
static inline void tlb_table_init(struct mmu_gather *tlb)
|
|
{
|
|
tlb->batch = NULL;
|
|
}
|
|
|
|
#else /* !CONFIG_MMU_GATHER_TABLE_FREE */
|
|
|
|
static inline void tlb_table_flush(struct mmu_gather *tlb) { }
|
|
static inline void tlb_table_init(struct mmu_gather *tlb) { }
|
|
|
|
#endif /* CONFIG_MMU_GATHER_TABLE_FREE */
|
|
|
|
static void tlb_flush_mmu_free(struct mmu_gather *tlb)
|
|
{
|
|
tlb_table_flush(tlb);
|
|
#ifndef CONFIG_MMU_GATHER_NO_GATHER
|
|
tlb_batch_pages_flush(tlb);
|
|
#endif
|
|
}
|
|
|
|
void tlb_flush_mmu(struct mmu_gather *tlb)
|
|
{
|
|
tlb_flush_mmu_tlbonly(tlb);
|
|
tlb_flush_mmu_free(tlb);
|
|
}
|
|
|
|
static void __tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
|
|
bool fullmm)
|
|
{
|
|
tlb->mm = mm;
|
|
tlb->fullmm = fullmm;
|
|
|
|
#ifndef CONFIG_MMU_GATHER_NO_GATHER
|
|
tlb->need_flush_all = 0;
|
|
tlb->local.next = NULL;
|
|
tlb->local.nr = 0;
|
|
tlb->local.max = ARRAY_SIZE(tlb->__pages);
|
|
tlb->active = &tlb->local;
|
|
tlb->batch_count = 0;
|
|
#endif
|
|
tlb->delayed_rmap = 0;
|
|
|
|
tlb_table_init(tlb);
|
|
#ifdef CONFIG_MMU_GATHER_PAGE_SIZE
|
|
tlb->page_size = 0;
|
|
#endif
|
|
|
|
__tlb_reset_range(tlb);
|
|
inc_tlb_flush_pending(tlb->mm);
|
|
}
|
|
|
|
/**
|
|
* tlb_gather_mmu - initialize an mmu_gather structure for page-table tear-down
|
|
* @tlb: the mmu_gather structure to initialize
|
|
* @mm: the mm_struct of the target address space
|
|
*
|
|
* Called to initialize an (on-stack) mmu_gather structure for page-table
|
|
* tear-down from @mm.
|
|
*/
|
|
void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm)
|
|
{
|
|
__tlb_gather_mmu(tlb, mm, false);
|
|
}
|
|
|
|
/**
|
|
* tlb_gather_mmu_fullmm - initialize an mmu_gather structure for page-table tear-down
|
|
* @tlb: the mmu_gather structure to initialize
|
|
* @mm: the mm_struct of the target address space
|
|
*
|
|
* In this case, @mm is without users and we're going to destroy the
|
|
* full address space (exit/execve).
|
|
*
|
|
* Called to initialize an (on-stack) mmu_gather structure for page-table
|
|
* tear-down from @mm.
|
|
*/
|
|
void tlb_gather_mmu_fullmm(struct mmu_gather *tlb, struct mm_struct *mm)
|
|
{
|
|
__tlb_gather_mmu(tlb, mm, true);
|
|
}
|
|
|
|
/**
|
|
* tlb_finish_mmu - finish an mmu_gather structure
|
|
* @tlb: the mmu_gather structure to finish
|
|
*
|
|
* Called at the end of the shootdown operation to free up any resources that
|
|
* were required.
|
|
*/
|
|
void tlb_finish_mmu(struct mmu_gather *tlb)
|
|
{
|
|
/*
|
|
* If there are parallel threads are doing PTE changes on same range
|
|
* under non-exclusive lock (e.g., mmap_lock read-side) but defer TLB
|
|
* flush by batching, one thread may end up seeing inconsistent PTEs
|
|
* and result in having stale TLB entries. So flush TLB forcefully
|
|
* if we detect parallel PTE batching threads.
|
|
*
|
|
* However, some syscalls, e.g. munmap(), may free page tables, this
|
|
* needs force flush everything in the given range. Otherwise this
|
|
* may result in having stale TLB entries for some architectures,
|
|
* e.g. aarch64, that could specify flush what level TLB.
|
|
*/
|
|
if (mm_tlb_flush_nested(tlb->mm)) {
|
|
/*
|
|
* The aarch64 yields better performance with fullmm by
|
|
* avoiding multiple CPUs spamming TLBI messages at the
|
|
* same time.
|
|
*
|
|
* On x86 non-fullmm doesn't yield significant difference
|
|
* against fullmm.
|
|
*/
|
|
tlb->fullmm = 1;
|
|
__tlb_reset_range(tlb);
|
|
tlb->freed_tables = 1;
|
|
}
|
|
|
|
tlb_flush_mmu(tlb);
|
|
|
|
#ifndef CONFIG_MMU_GATHER_NO_GATHER
|
|
tlb_batch_list_free(tlb);
|
|
#endif
|
|
dec_tlb_flush_pending(tlb->mm);
|
|
}
|