Messages in this thread Patch in this message | | | Date | Tue, 25 May 2021 09:39:31 -0700 | From | Minchan Kim <> | Subject | Re: [mm] 8cc621d2f4: fio.write_iops -21.8% regression |
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On Tue, May 25, 2021 at 08:16:03AM -0700, Minchan Kim wrote:
< snip >
> > > On Thu, May 20, 2021 at 04:31:44PM +0800, kernel test robot wrote: > > > > > > > > > > > > Greeting, > > > > > > > > FYI, we noticed a -21.8% regression of fio.write_iops due to commit: > > > > > > > > > > > > commit: 8cc621d2f45ddd3dc664024a647ee7adf48d79a5 ("mm: fs: > > > > invalidate BH LRU during page migration") > > > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master > > > > > > > > > > > > in testcase: fio-basic > > > > on test machine: 96 threads 2 sockets Intel(R) Xeon(R) Gold 6252 CPU > > > > @ 2.10GHz with 256G memory > > > > with following parameters: > > > > > > > > disk: 2pmem > > > > fs: ext4 > > > > runtime: 200s > > > > nr_task: 50% > > > > time_based: tb > > > > rw: randwrite > > > > bs: 4k > > > > ioengine: libaio > > > > test_size: 200G > > > > cpufreq_governor: performance > > > > ucode: 0x5003006 > > > > > > > > test-description: Fio is a tool that will spawn a number of threads > > > > or processes doing a particular type of I/O action as specified by > > > > the user. > > > > test-url: https://github.com/axboe/fio > > > > > > > > > > > > > > > > If you fix the issue, kindly add following tag > > > > Reported-by: kernel test robot <oliver.sang@intel.com> > > > > > > > > > > > > Details are as below: > > > > --------------------------------------------------------------------------------------------------> > > > > > > > > > > > > To reproduce: > > > > > > > > git clone https://github.com/intel/lkp-tests.git > > > > cd lkp-tests > > > > bin/lkp install job.yaml # job file is > > > > attached in this email > > > > bin/lkp split-job --compatible job.yaml # generate the yaml > > > > file for lkp run > > > > bin/lkp run generated-yaml-file > > > > > > Hi, > > > > > > I tried to insall the lkp-test in my machine by following above guide > > > but failed > > > due to package problems(I guess it's my problem since I use something > > > particular > > > environement). However, I guess it comes from increased miss ratio of > > > bh_lrus > > > since the patch caused more frequent invalidation of the bh_lrus calls > > > compared > > > to old. For example, lru_add_drain could be called from several hot > > > places(e.g., > > > unmap and pagevec_release from several path) and it could keeps > > > invalidating > > > bh_lrus. > > > > > > IMO, we should move the overhead from such hot path to cold one. How > > > about this? > > > > > > From ebf4ede1cf32fb14d85f0015a3693cb8e1b8dbfe Mon Sep 17 00:00:00 2001 > > > From: Minchan Kim <minchan@kernel.org> > > > Date: Thu, 20 May 2021 11:17:56 -0700 > > > Subject: [PATCH] invalidate bh_lrus only at lru_add_drain_all > > > > > > Not-Yet-Signed-off-by: Minchan Kim <minchan@kernel.org> > > > --- > > > mm/swap.c | 15 +++++++++++++-- > > > 1 file changed, 13 insertions(+), 2 deletions(-) > > > > > > diff --git a/mm/swap.c b/mm/swap.c > > > index dfb48cf9c2c9..d6168449e28c 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); > > > } > > > > > > +void lru_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); > > > +} > > > + > > > > Nit: drop int cpu? > > Do you mean to suggest using smp_processor_id at both places > instead of local varaible? Since the invalidate_bh_lrus_cpu > is called out of the lru_pvecs.lock, I wanted to express > the draining happens at the same CPU via storing the 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_and_bh_lrus_drain(); > > > } > > > > > > /* > > > @@ -881,6 +891,7 @@ void lru_cache_disable(void) > > > __lru_add_drain_all(true); > > > #else > > > lru_add_drain(); > > > + invalidate_bh_lrus_cpu(smp_processor_id()); > > > #endif > > > } > > > > Can't we replace the call to lru_add_drain() and > > invalidate_bh_lrus_cpu(smp_processor_id()) with a single call to > > lru_and_bh_lrus_drain()? > > Good idea.
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> Cc: 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
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