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9cecde80aa
On a 104 thread, 2 socket Skylake system, Intel report a 4.7% performance
reduction with will-it-scale page_fault2. This was due to reducing the
size of the batch from 32 to 15. Increasing the folio batch size from 15
to 31 gives a performance increase of 12.5% relative to the original, or
17.2% relative to the reduced performance commit.
The penalty of this commit is an additional 128 bytes of stack usage. Six
folio_batches are also allocated from percpu memory in cpu_fbatches so
that will be an additional 768 bytes of percpu memory (per CPU). Tim Chen
originally submitted a patch like this in 2020:
https://lore.kernel.org/linux-mm/d1cc9f12a8ad6c2a52cb600d93b06b064f2bbc57.1593205965.git.tim.c.chen@linux.intel.com/
Link: https://lkml.kernel.org/r/20240315140823.2478146-1-willy@infradead.org
Fixes: 99fbb6bfc1 ("mm: make folios_put() the basis of release_pages()")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Yujie Liu <yujie.liu@intel.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202403151058.7048f6a8-oliver.sang@intel.com
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
105 lines
2.6 KiB
C
105 lines
2.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* include/linux/pagevec.h
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*
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* In many places it is efficient to batch an operation up against multiple
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* folios. A folio_batch is a container which is used for that.
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*/
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#ifndef _LINUX_PAGEVEC_H
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#define _LINUX_PAGEVEC_H
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#include <linux/types.h>
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/* 31 pointers + header align the folio_batch structure to a power of two */
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#define PAGEVEC_SIZE 31
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struct folio;
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/**
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* struct folio_batch - A collection of folios.
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*
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* The folio_batch is used to amortise the cost of retrieving and
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* operating on a set of folios. The order of folios in the batch may be
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* significant (eg delete_from_page_cache_batch()). Some users of the
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* folio_batch store "exceptional" entries in it which can be removed
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* by calling folio_batch_remove_exceptionals().
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*/
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struct folio_batch {
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unsigned char nr;
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unsigned char i;
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bool percpu_pvec_drained;
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struct folio *folios[PAGEVEC_SIZE];
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};
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/**
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* folio_batch_init() - Initialise a batch of folios
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* @fbatch: The folio batch.
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*
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* A freshly initialised folio_batch contains zero folios.
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*/
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static inline void folio_batch_init(struct folio_batch *fbatch)
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{
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fbatch->nr = 0;
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fbatch->i = 0;
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fbatch->percpu_pvec_drained = false;
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}
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static inline void folio_batch_reinit(struct folio_batch *fbatch)
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{
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fbatch->nr = 0;
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fbatch->i = 0;
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}
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static inline unsigned int folio_batch_count(struct folio_batch *fbatch)
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{
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return fbatch->nr;
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}
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static inline unsigned int folio_batch_space(struct folio_batch *fbatch)
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{
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return PAGEVEC_SIZE - fbatch->nr;
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}
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/**
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* folio_batch_add() - Add a folio to a batch.
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* @fbatch: The folio batch.
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* @folio: The folio to add.
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*
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* The folio is added to the end of the batch.
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* The batch must have previously been initialised using folio_batch_init().
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*
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* Return: The number of slots still available.
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*/
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static inline unsigned folio_batch_add(struct folio_batch *fbatch,
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struct folio *folio)
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{
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fbatch->folios[fbatch->nr++] = folio;
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return folio_batch_space(fbatch);
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}
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/**
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* folio_batch_next - Return the next folio to process.
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* @fbatch: The folio batch being processed.
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*
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* Use this function to implement a queue of folios.
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*
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* Return: The next folio in the queue, or NULL if the queue is empty.
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*/
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static inline struct folio *folio_batch_next(struct folio_batch *fbatch)
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{
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if (fbatch->i == fbatch->nr)
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return NULL;
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return fbatch->folios[fbatch->i++];
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}
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void __folio_batch_release(struct folio_batch *pvec);
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static inline void folio_batch_release(struct folio_batch *fbatch)
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{
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if (folio_batch_count(fbatch))
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__folio_batch_release(fbatch);
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}
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void folio_batch_remove_exceptionals(struct folio_batch *fbatch);
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#endif /* _LINUX_PAGEVEC_H */
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