On Thu, Nov 19, 2020 at 11:34:32AM +0800, Zhenhua Huang wrote: > On Wed, Nov 04, 2020 at 07:27:03AM +0800, Minchan Kim wrote: > > Sorry if this mail corrupts the mail thread or had heavy mangling > > since I lost this mail from my mailbox so I am sending this mail by > > web gmail. > > > > On Thu, Oct 22, 2020 at 10:18 AM <vjitta@xxxxxxxxxxxxxx> wrote: > > > > > > From: Yogesh Lal <ylal@xxxxxxxxxxxxxx> > > > > > > Use STACK_HASH_ORDER_SHIFT to configure STACK_HASH_SIZE. > > > > > > Aim is to have configurable value for STACK_HASH_SIZE, > > > so depend on use case one can configure it. > > > > > > One example is of Page Owner, default value of > > > STACK_HASH_SIZE lead stack depot to consume 8MB of static memory. > > > Making it configurable and use lower value helps to enable features like > > > CONFIG_PAGE_OWNER without any significant overhead. > > > > > > Signed-off-by: Yogesh Lal <ylal@xxxxxxxxxxxxxx> > > > Signed-off-by: Vinayak Menon <vinmenon@xxxxxxxxxxxxxx> > > > Signed-off-by: Vijayanand Jitta <vjitta@xxxxxxxxxxxxxx> > > > --- > > > lib/Kconfig | 9 +++++++++ > > > lib/stackdepot.c | 3 +-- > > > 2 files changed, 10 insertions(+), 2 deletions(-) > > > > > > diff --git a/lib/Kconfig b/lib/Kconfig > > > index 18d76b6..b3f8259 100644 > > > --- a/lib/Kconfig > > > +++ b/lib/Kconfig > > > @@ -651,6 +651,15 @@ config STACKDEPOT > > > bool > > > select STACKTRACE > > > > > > +config STACK_HASH_ORDER_SHIFT > > > + int "stack depot hash size (12 => 4KB, 20 => 1024KB)" > > > + range 12 20 > > > + default 20 > > > + depends on STACKDEPOT > > > + help > > > + Select the hash size as a power of 2 for the stackdepot hash > > > table. > > > + Choose a lower value to reduce the memory impact. > > > + > > > config SBITMAP > > > bool > > > > > > diff --git a/lib/stackdepot.c b/lib/stackdepot.c > > > index 2caffc6..413c20b 100644 > > > --- a/lib/stackdepot.c > > > +++ b/lib/stackdepot.c > > > @@ -142,8 +142,7 @@ static struct stack_record *depot_alloc_stack(unsigned > > > long *entries, int size, > > > return stack; > > > } > > > > > > -#define STACK_HASH_ORDER 20 > > > -#define STACK_HASH_SIZE (1L << STACK_HASH_ORDER) > > > +#define STACK_HASH_SIZE (1L << CONFIG_STACK_HASH_ORDER_SHIFT) > > > #define STACK_HASH_MASK (STACK_HASH_SIZE - 1) > > > #define STACK_HASH_SEED 0x9747b28c > > > > > > -- > > > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member > > > of Code Aurora Forum, hosted by The Linux Foundation > > > 2.7.4 > > > > > > > 1. When we don't use page_owner, we don't want to waste any memory for > > stackdepot hash array. > > 2. When we use page_owner, we want to have reasonable stackdeport hash array > > > > With this configuration, it couldn't meet since we always need to > > reserve a reasonable size for the array. > > Can't we make the hash size as a kernel parameter? > > With it, we could use it like this. > > > > 1. page_owner=off, stackdepot_stack_hash=0 -> no more wasted memory > > when we don't use page_owner > > 2. page_owner=on, stackdepot_stack_hash=8M -> reasonable hash size > > when we use page_owner. > Seems we have other users like kasan, and dma_buf_ref which we introduced. > Also we can't guarantee there will not be any other users for stackdepot, so > it's better we not depend on only page owner? I didn't mean to make it page_owner dependent. What I suggested is just to define kernel parameter for stackdeport hash size so admin could override it at right size when we really need it.
