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![Uladzislau Rezki (Sony)](/assets/img/avatar_default.png)
A current "lazy drain" model suffers from at least two issues. First one is related to the unsorted list of vmap areas, thus in order to identify the [min:max] range of areas to be drained, it requires a full list scan. What is a time consuming if the list is too long. Second one and as a next step is about merging all fragments with a free space. What is also a time consuming because it has to iterate over entire list which holds outstanding lazy areas. See below the "preemptirqsoff" tracer that illustrates a high latency. It is ~24676us. Our workloads like audio and video are effected by such long latency: <snip> tracer: preemptirqsoff preemptirqsoff latency trace v1.1.5 on 4.9.186-perf+ -------------------------------------------------------------------- latency: 24676 us, #4/4, CPU#1 | (M:preempt VP:0, KP:0, SP:0 HP:0 P:8) ----------------- | task: crtc_commit:112-261 (uid:0 nice:0 policy:1 rt_prio:16) ----------------- => started at: __purge_vmap_area_lazy => ended at: __purge_vmap_area_lazy _------=> CPU# / _-----=> irqs-off | / _----=> need-resched || / _---=> hardirq/softirq ||| / _--=> preempt-depth |||| / delay cmd pid ||||| time | caller \ / ||||| \ | / crtc_com-261 1...1 1us*: _raw_spin_lock <-__purge_vmap_area_lazy [...] crtc_com-261 1...1 24675us : _raw_spin_unlock <-__purge_vmap_area_lazy crtc_com-261 1...1 24677us : trace_preempt_on <-__purge_vmap_area_lazy crtc_com-261 1...1 24683us : <stack trace> => free_vmap_area_noflush => remove_vm_area => __vunmap => vfree => drm_property_free_blob => drm_mode_object_unreference => drm_property_unreference_blob => __drm_atomic_helper_crtc_destroy_state => sde_crtc_destroy_state => drm_atomic_state_default_clear => drm_atomic_state_clear => drm_atomic_state_free => complete_commit => _msm_drm_commit_work_cb => kthread_worker_fn => kthread => ret_from_fork <snip> To address those two issues we can redesign a purging of the outstanding lazy areas. Instead of queuing vmap areas to the list, we replace it by the separate rb-tree. In hat case an area is located in the tree/list in ascending order. It will give us below advantages: a) Outstanding vmap areas are merged creating bigger coalesced blocks, thus it becomes less fragmented. b) It is possible to calculate a flush range [min:max] without scanning all elements. It is O(1) access time or complexity; c) The final merge of areas with the rb-tree that represents a free space is faster because of (a). As a result the lock contention is also reduced. Link: https://lkml.kernel.org/r/20201116220033.1837-2-urezki@gmail.com Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Cc: Hillf Danton <hdanton@sina.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Minchan Kim <minchan@kernel.org> Cc: huang ying <huang.ying.caritas@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
249 lines
7.6 KiB
C
249 lines
7.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_VMALLOC_H
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#define _LINUX_VMALLOC_H
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#include <linux/spinlock.h>
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#include <linux/init.h>
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#include <linux/list.h>
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#include <linux/llist.h>
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#include <asm/page.h> /* pgprot_t */
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#include <linux/rbtree.h>
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#include <linux/overflow.h>
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#include <asm/vmalloc.h>
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struct vm_area_struct; /* vma defining user mapping in mm_types.h */
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struct notifier_block; /* in notifier.h */
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/* bits in flags of vmalloc's vm_struct below */
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#define VM_IOREMAP 0x00000001 /* ioremap() and friends */
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#define VM_ALLOC 0x00000002 /* vmalloc() */
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#define VM_MAP 0x00000004 /* vmap()ed pages */
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#define VM_USERMAP 0x00000008 /* suitable for remap_vmalloc_range */
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#define VM_DMA_COHERENT 0x00000010 /* dma_alloc_coherent */
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#define VM_UNINITIALIZED 0x00000020 /* vm_struct is not fully initialized */
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#define VM_NO_GUARD 0x00000040 /* don't add guard page */
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#define VM_KASAN 0x00000080 /* has allocated kasan shadow memory */
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#define VM_MAP_PUT_PAGES 0x00000100 /* put pages and free array in vfree */
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/*
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* VM_KASAN is used slighly differently depending on CONFIG_KASAN_VMALLOC.
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*
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* If IS_ENABLED(CONFIG_KASAN_VMALLOC), VM_KASAN is set on a vm_struct after
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* shadow memory has been mapped. It's used to handle allocation errors so that
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* we don't try to poision shadow on free if it was never allocated.
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*
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* Otherwise, VM_KASAN is set for kasan_module_alloc() allocations and used to
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* determine which allocations need the module shadow freed.
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*/
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/*
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* Memory with VM_FLUSH_RESET_PERMS cannot be freed in an interrupt or with
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* vfree_atomic().
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*/
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#define VM_FLUSH_RESET_PERMS 0x00000100 /* Reset direct map and flush TLB on unmap */
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/* bits [20..32] reserved for arch specific ioremap internals */
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/*
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* Maximum alignment for ioremap() regions.
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* Can be overriden by arch-specific value.
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*/
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#ifndef IOREMAP_MAX_ORDER
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#define IOREMAP_MAX_ORDER (7 + PAGE_SHIFT) /* 128 pages */
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#endif
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struct vm_struct {
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struct vm_struct *next;
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void *addr;
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unsigned long size;
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unsigned long flags;
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struct page **pages;
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unsigned int nr_pages;
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phys_addr_t phys_addr;
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const void *caller;
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};
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struct vmap_area {
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unsigned long va_start;
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unsigned long va_end;
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struct rb_node rb_node; /* address sorted rbtree */
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struct list_head list; /* address sorted list */
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/*
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* The following two variables can be packed, because
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* a vmap_area object can be either:
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* 1) in "free" tree (root is vmap_area_root)
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* 2) or "busy" tree (root is free_vmap_area_root)
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*/
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union {
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unsigned long subtree_max_size; /* in "free" tree */
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struct vm_struct *vm; /* in "busy" tree */
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};
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};
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/*
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* Highlevel APIs for driver use
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*/
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extern void vm_unmap_ram(const void *mem, unsigned int count);
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extern void *vm_map_ram(struct page **pages, unsigned int count, int node);
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extern void vm_unmap_aliases(void);
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#ifdef CONFIG_MMU
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extern void __init vmalloc_init(void);
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extern unsigned long vmalloc_nr_pages(void);
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#else
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static inline void vmalloc_init(void)
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{
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}
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static inline unsigned long vmalloc_nr_pages(void) { return 0; }
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#endif
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extern void *vmalloc(unsigned long size);
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extern void *vzalloc(unsigned long size);
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extern void *vmalloc_user(unsigned long size);
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extern void *vmalloc_node(unsigned long size, int node);
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extern void *vzalloc_node(unsigned long size, int node);
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extern void *vmalloc_32(unsigned long size);
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extern void *vmalloc_32_user(unsigned long size);
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extern void *__vmalloc(unsigned long size, gfp_t gfp_mask);
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extern void *__vmalloc_node_range(unsigned long size, unsigned long align,
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unsigned long start, unsigned long end, gfp_t gfp_mask,
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pgprot_t prot, unsigned long vm_flags, int node,
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const void *caller);
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void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask,
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int node, const void *caller);
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extern void vfree(const void *addr);
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extern void vfree_atomic(const void *addr);
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extern void *vmap(struct page **pages, unsigned int count,
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unsigned long flags, pgprot_t prot);
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void *vmap_pfn(unsigned long *pfns, unsigned int count, pgprot_t prot);
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extern void vunmap(const void *addr);
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extern int remap_vmalloc_range_partial(struct vm_area_struct *vma,
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unsigned long uaddr, void *kaddr,
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unsigned long pgoff, unsigned long size);
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extern int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
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unsigned long pgoff);
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/*
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* Architectures can set this mask to a combination of PGTBL_P?D_MODIFIED values
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* and let generic vmalloc and ioremap code know when arch_sync_kernel_mappings()
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* needs to be called.
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*/
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#ifndef ARCH_PAGE_TABLE_SYNC_MASK
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#define ARCH_PAGE_TABLE_SYNC_MASK 0
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#endif
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/*
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* There is no default implementation for arch_sync_kernel_mappings(). It is
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* relied upon the compiler to optimize calls out if ARCH_PAGE_TABLE_SYNC_MASK
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* is 0.
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*/
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void arch_sync_kernel_mappings(unsigned long start, unsigned long end);
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/*
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* Lowlevel-APIs (not for driver use!)
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*/
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static inline size_t get_vm_area_size(const struct vm_struct *area)
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{
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if (!(area->flags & VM_NO_GUARD))
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/* return actual size without guard page */
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return area->size - PAGE_SIZE;
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else
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return area->size;
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}
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extern struct vm_struct *get_vm_area(unsigned long size, unsigned long flags);
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extern struct vm_struct *get_vm_area_caller(unsigned long size,
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unsigned long flags, const void *caller);
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extern struct vm_struct *__get_vm_area_caller(unsigned long size,
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unsigned long flags,
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unsigned long start, unsigned long end,
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const void *caller);
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void free_vm_area(struct vm_struct *area);
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extern struct vm_struct *remove_vm_area(const void *addr);
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extern struct vm_struct *find_vm_area(const void *addr);
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#ifdef CONFIG_MMU
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extern int map_kernel_range_noflush(unsigned long start, unsigned long size,
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pgprot_t prot, struct page **pages);
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int map_kernel_range(unsigned long start, unsigned long size, pgprot_t prot,
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struct page **pages);
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extern void unmap_kernel_range_noflush(unsigned long addr, unsigned long size);
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extern void unmap_kernel_range(unsigned long addr, unsigned long size);
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static inline void set_vm_flush_reset_perms(void *addr)
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{
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struct vm_struct *vm = find_vm_area(addr);
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if (vm)
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vm->flags |= VM_FLUSH_RESET_PERMS;
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}
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#else
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static inline int
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map_kernel_range_noflush(unsigned long start, unsigned long size,
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pgprot_t prot, struct page **pages)
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{
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return size >> PAGE_SHIFT;
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}
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#define map_kernel_range map_kernel_range_noflush
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static inline void
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unmap_kernel_range_noflush(unsigned long addr, unsigned long size)
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{
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}
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#define unmap_kernel_range unmap_kernel_range_noflush
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static inline void set_vm_flush_reset_perms(void *addr)
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{
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}
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#endif
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/* for /dev/kmem */
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extern long vread(char *buf, char *addr, unsigned long count);
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extern long vwrite(char *buf, char *addr, unsigned long count);
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/*
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* Internals. Dont't use..
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*/
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extern struct list_head vmap_area_list;
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extern __init void vm_area_add_early(struct vm_struct *vm);
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extern __init void vm_area_register_early(struct vm_struct *vm, size_t align);
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#ifdef CONFIG_SMP
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# ifdef CONFIG_MMU
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struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
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const size_t *sizes, int nr_vms,
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size_t align);
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void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms);
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# else
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static inline struct vm_struct **
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pcpu_get_vm_areas(const unsigned long *offsets,
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const size_t *sizes, int nr_vms,
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size_t align)
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{
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return NULL;
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}
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static inline void
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pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
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{
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}
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# endif
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#endif
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#ifdef CONFIG_MMU
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#define VMALLOC_TOTAL (VMALLOC_END - VMALLOC_START)
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#else
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#define VMALLOC_TOTAL 0UL
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#endif
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int register_vmap_purge_notifier(struct notifier_block *nb);
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int unregister_vmap_purge_notifier(struct notifier_block *nb);
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#endif /* _LINUX_VMALLOC_H */
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