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https://github.com/checkpoint-restore/criu
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bb98a82098
The problem is that vmsplice() to a big pipe fails very often. The kernel allocates a linear chunk of memory for pipe buffer descriptos, but a big allocation in kernel can fail. So we need to restrict maximal capacity of pipes. But the number of pipes is restricted too, so we need to split dumping memory on chunks. In this patch we calculates the pipe size for which vmsplice() will not fail. v2: s/batch/chunk and a few other small fixes v3: Remove callbacks from page_pipes and reuse pipes Signed-off-by: Andrey Vagin <avagin@openvz.org> Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
108 lines
3.2 KiB
C
108 lines
3.2 KiB
C
#ifndef __CR_PAGE_PIPE_H__
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#define __CR_PAGE_PIPE_H__
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#include <sys/uio.h>
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#include "list.h"
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/*
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* page_pipe is a descriptor of task's virtual memory
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* with pipes, containing pages.
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*
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* A page-pipe may contain holes -- these are pagemap
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* entries without pages. Holes are stored in separate
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* array to optimize paged iovs feed into vmsplice --
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* they will be sent there in one go.
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*
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* A hole is a pagemap entry that doesn't have pages
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* in it, since they are present in previous (parent)
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* snapshot.
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*
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*
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* This page-pipe vs holes vs task vmem vs image layout
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* is described below.
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*
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* Task memory: (+ present, - not present pages)
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* 0 0 0 0 1 1 1
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* 0 3 6 B 1 8 C
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* ---+++-----++++++-------++++----
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*
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* Page-pipe iovs:
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*
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* bufs = 03:3,0B:6,18:4
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* holes = <empty>
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*
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* The pagemap.img would purely contain page-pipe bufs.
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*
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* Pages image will contain pages at
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*
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* 03,04,05,0B,0C,0D,0E,0F,10,18,19,1A,1B
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*
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* stored one by one.
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*
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* Not let's imagine task touches some pages and its mem
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* looks like: (+ present, = old present, - non present)
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*
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* 0 0 0 0 11 11 1
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* 0 3 6 B 12 78 C
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* ---==+-----====+++-----++===----
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*
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* (not new pages at 11 and 17 vaddrs)
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*
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* The new --snapshot'ed page-pipe would look like
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*
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* bufs = 05:1,0F:3,17:2
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* holes = 03:2,0B:4,19:3
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*
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* So the pagemap.img would look like
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*
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* 03:2:P,05:1,0B:4:P,0F:3,17:2,19:3:P
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*
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* (the page_xfer_dump_pages generates one)
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*
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* where P means "in parent", i.e. respective pages should
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* be looked up in the parent pagemap (not pages.img, but
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* the pagemap, and then the offset in previous pages.img
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* should be calculated, see the read_pagemap_page routine).
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*
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* New pages.img file would contain only pages for
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*
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* 05,0F,10,11,17,18
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*/
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struct page_pipe_buf {
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int p[2]; /* pipe with pages */
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unsigned int pipe_size; /* how many pages can be fit into pipe */
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unsigned int pages_in; /* how many pages are there */
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unsigned int nr_segs; /* how many iov-s are busy */
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struct iovec *iov; /* vaddr:len map */
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struct list_head l; /* links into page_pipe->bufs */
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};
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struct page_pipe {
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unsigned int nr_pipes; /* how many page_pipe_bufs in there */
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struct list_head bufs; /* list of bufs */
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struct list_head free_bufs; /* list of bufs */
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unsigned int nr_iovs; /* number of iovs */
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unsigned int free_iov; /* first free iov */
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struct iovec *iovs; /* iovs. They are provided into create_page_pipe
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and all bufs have their iov-s in there */
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unsigned int nr_holes; /* number of holes allocated */
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unsigned int free_hole; /* number of holes in use */
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struct iovec *holes; /* holes */
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bool chunk_mode; /* Restrict the maximum buffer size of pipes
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and dump memory for a few iterations */
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};
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extern struct page_pipe *create_page_pipe(unsigned int nr,
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struct iovec *, bool chunk_mode);
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extern void destroy_page_pipe(struct page_pipe *p);
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extern int page_pipe_add_page(struct page_pipe *p, unsigned long addr);
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extern int page_pipe_add_hole(struct page_pipe *p, unsigned long addr);
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extern void debug_show_page_pipe(struct page_pipe *pp);
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void page_pipe_reinit(struct page_pipe *pp);
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#endif /* __CR_PAGE_PIPE_H__ */
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