Messages in this thread Patch in this message | | | Date | Tue, 07 Sep 2021 11:46:02 -0700 | From | Chris Goldsworthy <> | Subject | Re: [LKP] Re: [mm] 8cc621d2f4: fio.write_iops -21.8% regression |
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On 2021-09-07 09:55, Minchan Kim wrote: > Hi, > > On Fri, Sep 03, 2021 at 03:11:33PM +0800, Xing, Zhengjun wrote: >> Hi Minchan, >> >> Do you have time to look at this? I re-test it in v5.14, the >> regression >> still existed. Thanks. > > Reminding me the issue, again, Xing. That's because the patch > was not merged yet so let me send it again. > > Andrew? > > From 8caadeb49d82403a08643dfbdb0b7749017c00bb Mon Sep 17 00:00:00 2001 > From: Minchan Kim <minchan@kernel.org> > Date: Tue, 25 May 2021 08:19:17 -0700 > Subject: [PATCH] mm: fs: invalidate bh_lrus for only cold path > > kernel test robot reported the regression of fio.write_iops[1] > with [2]. > > 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). > > [1] > https://lore.kernel.org/lkml/20210520083144.GD14190@xsang-OptiPlex-9020/ > [2] 8cc621d2f45d, mm: fs: invalidate BH LRU during page migration > Cc: Xing, Zhengjun <zhengjun.xing@intel.com> > Reviewed-by: Chris Goldsworthy <cgoldswo@codeaurora.org> > Reported-by: kernel test robot <oliver.sang@intel.com> > Signed-off-by: Minchan Kim <minchan@kernel.org> > --- > mm/swap.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > > diff --git a/mm/swap.c b/mm/swap.c > index 1958d5feb148..3e25d99a9dbb 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -642,7 +642,6 @@ void lru_add_drain_cpu(int cpu) > pagevec_lru_move_fn(pvec, lru_lazyfree_fn); > > activate_page_drain(cpu); > - invalidate_bh_lrus_cpu(cpu); > } > > /** > @@ -725,6 +724,17 @@ void lru_add_drain(void) > local_unlock(&lru_pvecs.lock); > } > > +static void lru_add_and_bh_lrus_drain(void) > +{ > + int cpu; > + > + local_lock(&lru_pvecs.lock); > + cpu = smp_processor_id(); > + lru_add_drain_cpu(cpu); > + local_unlock(&lru_pvecs.lock); > + invalidate_bh_lrus_cpu(cpu); > +} > + > void lru_add_drain_cpu_zone(struct zone *zone) > { > local_lock(&lru_pvecs.lock); > @@ -739,7 +749,7 @@ 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(); > } > > /* > @@ -880,7 +890,7 @@ void lru_cache_disable(void) > */ > __lru_add_drain_all(true); > #else > - lru_add_drain(); > + lru_add_and_bh_lrus_drain(); > #endif > } > > -- > 2.31.1.818.g46aad6cb9e-goog
Hi Minchan,
I believe that was the first iteration of your patch - there was some further feedback, such that this was the last version you submitted:
From 8d58e7ade3ed6c080995dec1395b1e130b3d16b3 Mon Sep 17 00:00:00 2001 From: Minchan Kim <minchan@kernel.org> Date: Tue, 25 May 2021 08:19:17 -0700 Subject: [PATCH] mm: fs: invalidate bh_lrus for only cold path
kernel test robot reported the regression of fio.write_iops[1] with [2].
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).
[1] https://lore.kernel.org/lkml/20210520083144.GD14190@xsang-OptiPlex-9020/ [2] 8cc621d2f45d, mm: fs: invalidate BH LRU during page migration Reported-by: kernel test robot <oliver.sang@intel.com> Signed-off-by: Minchan Kim <minchan@kernel.org> --- fs/buffer.c | 8 ++++++-- include/linux/buffer_head.h | 4 ++-- mm/swap.c | 19 ++++++++++++++++--- 3 files changed, 24 insertions(+), 7 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c index 673cfbef9eec..bdaffed39030 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -1487,12 +1487,16 @@ 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(); } diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index e7e99da31349..b04d34bab124 100644 --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -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 0; } #define buffer_heads_over_limit 0
diff --git a/mm/swap.c b/mm/swap.c index 1958d5feb148..4d9ec3c3c5a9 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -642,7 +642,6 @@ void lru_add_drain_cpu(int cpu) pagevec_lru_move_fn(pvec, lru_lazyfree_fn);
activate_page_drain(cpu); - invalidate_bh_lrus_cpu(cpu); }
/** @@ -725,6 +724,20 @@ 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); @@ -739,7 +752,7 @@ 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(); }
/* @@ -880,7 +893,7 @@ void lru_cache_disable(void) */ __lru_add_drain_all(true); #else - lru_add_drain(); + lru_add_and_bh_lrus_drain(); #endif }
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