Commit 243418e3 authored by Minchan Kim's avatar Minchan Kim Committed by Linus Torvalds
Browse files

mm: fs: invalidate bh_lrus for only cold path 

The kernel test robot reported the regression of fio.write_iops[1] with
commit 8cc621d2 ("mm: fs: invalidate BH LRU during page migration").

Since lru_add_drain is called frequently, invalidate bh_lrus there could
increase bh_lrus cache miss ratio, which needs more IO in the end.

This patch moves the bh_lrus invalidation from the hot path( e.g.,
zap_page_range, pagevec_release) to cold path(i.e., lru_add_drain_all,
lru_cache_disable).

Zhengjun Xing confirmed
 "I test the patch, the regression reduced to -2.9%"

[1] https://lore.kernel.org/lkml/20210520083144.GD14190@xsang-OptiPlex-9020/
[2] 8cc621d2, mm: fs: invalidate BH LRU during page migration

Link: https://lkml.kernel.org/r/20210907212347.1977686-1-minchan@kernel.org


Signed-off-by: default avatarMinchan Kim <minchan@kernel.org>
Reported-by: default avatarkernel test robot <oliver.sang@intel.com>
Reviewed-by: default avatarChris Goldsworthy <cgoldswo@codeaurora.org>
Tested-by: default avatar"Xing, Zhengjun" <zhengjun.xing@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b7cd9fa5

fs/buffer.c

+6 −2
Original line number Diff line number Diff line
@@ -1425,12 +1425,16 @@ void invalidate_bh_lrus(void) 
}

EXPORT_SYMBOL_GPL(invalidate_bh_lrus);



void invalidate_bh_lrus_cpu(int cpu)

/*

 * It's called from workqueue context so we need a bh_lru_lock to close

 * the race with preemption/irq.

 */

void invalidate_bh_lrus_cpu(void)

{

	struct bh_lru *b;



	bh_lru_lock();

	b = per_cpu_ptr(&bh_lrus, cpu);

	b = this_cpu_ptr(&bh_lrus);

	__invalidate_bh_lrus(b);

	bh_lru_unlock();

}

include/linux/buffer_head.h

+2 −2
Original line number Diff line number Diff line
@@ -194,7 +194,7 @@ void __breadahead_gfp(struct block_device *, sector_t block, unsigned int size, 
struct buffer_head *__bread_gfp(struct block_device *,

				sector_t block, unsigned size, gfp_t gfp);

void invalidate_bh_lrus(void);

void invalidate_bh_lrus_cpu(int cpu);

void invalidate_bh_lrus_cpu(void);

bool has_bh_in_lru(int cpu, void *dummy);

struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);

void free_buffer_head(struct buffer_head * bh);
@@ -408,7 +408,7 @@ static inline int inode_has_buffers(struct inode *inode) { return 0; } 
static inline void invalidate_inode_buffers(struct inode *inode) {}

static inline int remove_inode_buffers(struct inode *inode) { return 1; }

static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }

static inline void invalidate_bh_lrus_cpu(int cpu) {}

static inline void invalidate_bh_lrus_cpu(void) {}

static inline bool has_bh_in_lru(int cpu, void *dummy) { return false; }

#define buffer_heads_over_limit 0

mm/swap.c

+16 −3
Original line number Diff line number Diff line
@@ -620,7 +620,6 @@ void lru_add_drain_cpu(int cpu) 
		pagevec_lru_move_fn(pvec, lru_lazyfree_fn);



	activate_page_drain(cpu);

	invalidate_bh_lrus_cpu(cpu);

}



/**
@@ -703,6 +702,20 @@ void lru_add_drain(void) 
	local_unlock(&lru_pvecs.lock);

}



/*

 * It's called from per-cpu workqueue context in SMP case so

 * lru_add_drain_cpu and invalidate_bh_lrus_cpu should run on

 * the same cpu. It shouldn't be a problem in !SMP case since

 * the core is only one and the locks will disable preemption.

 */

static void lru_add_and_bh_lrus_drain(void)

{

	local_lock(&lru_pvecs.lock);

	lru_add_drain_cpu(smp_processor_id());

	local_unlock(&lru_pvecs.lock);

	invalidate_bh_lrus_cpu();

}



void lru_add_drain_cpu_zone(struct zone *zone)

{

	local_lock(&lru_pvecs.lock);
@@ -717,7 +730,7 @@ static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work); 


static void lru_add_drain_per_cpu(struct work_struct *dummy)

{

	lru_add_drain();

	lru_add_and_bh_lrus_drain();

}



/*
@@ -858,7 +871,7 @@ void lru_cache_disable(void) 
	 */

	__lru_add_drain_all(true);

#else

	lru_add_drain();

	lru_add_and_bh_lrus_drain();

#endif

}