Messages in this thread | | | Date | Tue, 25 May 2021 08:16:03 -0700 | From | Minchan Kim <> | Subject | Re: [mm] 8cc621d2f4: fio.write_iops -21.8% regression |
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On Mon, May 24, 2021 at 10:37:49AM -0700, Chris Goldsworthy wrote: > Hi Minchan, > > This looks good to me, I just have some minor feedback. > > Thanks,
Hi Chris,
Thanks for the review. Please see below.
> > Chris. > > On 2021-05-20 11:36, Minchan Kim wrote: > > 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.
Thanks!
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